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Crystal structure reinvestigation and spectroscopic analysis of tricadmium orthophosphate

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aLaboratoire de Chimie Appliquée des Matériaux, Centre des Sciences des Matériaux, Faculty of Science, Mohammed V University in Rabat, Avenue Ibn Batouta, BP 1014, Rabat, Morocco, and bLaboratoire de Physico-Chimie des Matériaux Inorganiques et Organiques, Centre des Sciences des Matériaux, Ecole Normale Supérieure, Mohammed V University in Rabat, Morocco
*Correspondence e-mail: fatimazahra_cherif@um5.ac.ma

Edited by L. Suescun, Universidad de la República, Uruguay (Received 10 October 2023; accepted 8 November 2023; online 14 November 2023)

This article is part of a collection of articles to commemorate the founding of the African Crystallographic Association and the 75th anniversary of the IUCr.

Single crystals of tricadmium orthophosphate, Cd3(PO4)2, have been synthesized successfully by the hydro­thermal route, while its powder form was obtained by a solid-solid process. The corresponding crystal structure was determined using X-ray diffraction data in the monoclinic space group P21/n. The crystal structure consists of Cd2O8 or Cd2O10 dimers linked together by PO4 tetra­hedra through sharing vertices or edges. Scanning electron microscopy (SEM) was used to investigate the morphology and to confirm the chemical composition of the synthesized powder. Infrared analysis corroborates the presence of isolated phosphate tetra­hedrons in the structure. UV–Visible studies showed an absorbance peak at 289 nm and a band gap energy of 3.85 eV, as determined by the Kubelka–Munk model.

1. Chemical context

Phosphates with transition metals have received significant attention due to their wide range of potential applications in different fields of technology such as farming, energy storage, and in the medical field, as medicines or for diagnosis. For instance, Ni3(PO4)2 was identified as a heat-sensitive pigment and a catalyst for breaking and de­hydrogenating aliphatic hydro­carbons (Correcher et al., 2013[Correcher, V., Isasi, J., Cubero, A., Pérez, M., Aldama, I., Arévalo, P., Castillo, J. F. & Garcia-Guinea, J. (2013). J. Phys. Chem. Solids, 74, 1678-1682.]), while the orthophosphates Zn3(PO4)2 and Cu3(PO4)2 have been applied in dentistry as a component of tooth fillings and environmental contamination control (Servais & Cartz, 1971[Servais, G. E. & Cartz, L. (1971). J. Dent. Res. 50, 613-620.] and Rong et al. 2017[Rong, J., Zhang, T., Qiu, F. & Zhu, Y. (2017). ACS Sustainable Chem. Eng. 5, 4468-4477. https://doi.org/10.1021/acssuschemeng.8b01469]), respectively. The aim of this paper is to provide a comprehensive discussion on the crystallographic arrangement of the β-Cd3(PO4)2 structure and to supply a full crystallographic description. Additionally, we will present the findings of our investigations into the compound's optical and morphological properties.

2. Structural commentary

Structural study

On the basis of the single crystal X-ray diffraction data analysis, the tri-cadmium orthophosphate crystallizes in the monoclinic system, space group P21/n. In this phosphate structure, all cadmium, phospho­rus and oxygen atoms occupy the general Wyckoff positions 4e. The anisotropic refinement of all atoms belonging to the crystal structure of β-Cd3(PO4)2 leads to excellent merit factors {R[F2 > 2σ(F2)] = 0.023, wR(F2) = 0.054 and S = 1.07}, which corroborate the adopted crystallographic model.

Structural description

The crystal structure of β-Cd3(PO4)2 presents a 3D framework constructed from isolated PO4 tetra­hedra and two different types of cadmium polyhedra, of coordination numbers five and six. The cadmium polyhedra are linked together to form a 3D framework. In this crystal structure, six of the nine cadmium atoms (Cd1, Cd2, Cd3, Cd4, Cd5, and Cd6) are located inside five-vertex polyhedra, with Cd—O bond lengths ranging from 2.1454 (19) to 2.3996 (18) Å, and averaging 2.2613 Å. The remaining three cadmium atoms (Cd7, Cd8, and Cd9) are located at the centers of six vertex polyhedra, with Cd—O bond lengths ranging from 2.2156 (17) to 2.5935 (19) Å, and averaging 2.3282 Å. The nearly regular phosphate tetra­hedra in the structure have P—O bond lengths ranging from 1.527 (2) to 1.557 (2) Å, and averaging 1.538 Å. On the other hand, while Stephens (1967[Stephens, J. S. (1967). Doctor of Philosophy Thesis, McMaster University, Hamilton, Ontario (May, 1967).]) noted irregularities in the PO4 tetra­hedra due to incomplete refinement of the structure, in this case the structure has been fully refined and the PO4 tetra­hedra are all regular as shown by the bond lengths and the inter­atomic angles recorded in the supporting information.

The calculated bond-valence-sum (BVS) values (Brown & Altermatt, 1985[Brown, I. D. & Altermatt, D. (1985). Acta Cryst. B41, 244-247.]) of all atoms in the crystal structure are in good agreement with the expected valence states of +5 for each of the six phospho­rus atoms, +2 for each of the nine cadmium atoms. and almost −2 for all oxygen atoms except O6 (BVS −1.669). Nevertheless, we see that all oxygen atoms are each linked to one phospho­rus atom and two cadmium atoms except O6, which is linked to one phospho­rus atom and a single cadmium atom. In this context, if we take into account the contribution of the two cadmiums located at distances of 2.729 and 2.731 Å, the BVS (O6) will be equal to −1.884. This indicates that the structure is nearly ionic, with each ion donating or accepting the expected number of valence electrons.

This phosphate has a complex crystal structure composed of almost regular PO4 tetra­hedra linked to two different types of distorted cadmium polyhedra arranged in a specific pattern to form a three-dimensional framework with small tunnels along the a-axis direction (see Fig. 1[link]). Moreover, the anionic network is formed by layers of PO4 tetra­hedra stacked nearly along the [[\overline{1}]01] direction and the cadmium polyhedra fill the remaining space as shown in Fig. 2[link]. Furthermore, the description of the sequence of the cadmium polyhedra is not easy. Indeed the polyhedra surrounding the cations (Cd2, Cd4 and Cd9) and (Cd5, Cd6 and Cd8) form two successive layers parallel to the ab plane (Fig. 3[link]a). The first layer of the framework consists of Cd2O5, Cd4O5 and Cd9O6 polyhedra, forming a ring of eight polyhedra two pairs of square-based prisms that share an edge and four pyramids linked by the vertices (Fig. 3[link]b). The second layer is composed of two Cd5O5, Cd6O5 pyramids and a deformed Cd8O6 octa­hedron arranged to share corners (Fig. 3[link]c). This layer is connected to the first layer to form a 3D framework with tunnels along the a-axis direction (Fig. 3[link]d). The zigzag chain composed of the remaining cadmium polyhedra, namely two pyramids, Cd1O5, Cd3O5, and the Cd7O6 prism fills the large tunnels of the framework (Fig. 3[link]e). The polyhedra belonging to this chain share the edges or vertices and form a zigzag pattern in the tunnels, which consolidates the connection of the two layers. Moreover, a more laborious examination of the structure shows that the four groups of cadmium polyhedra Cd5O5–Cd7O6–Cd1O5–Cd6O5 share edges to form slabs, which are linked together by the corners to build an infinite zigzag chain along the a-axis direction, as shown in Fig. 3[link]f.

[Figure 1]
Figure 1
Three-dimensional view the β-Cd3(PO4)2 crystal structure showing small tunnels along the a-axis direction.
[Figure 2]
Figure 2
The anionic network of β-Cd3(PO4)2, formed by layers of PO4 tetra­hedra stacked along the [[\overline{1}]01] direction.
[Figure 3]
Figure 3
Schematic representation of the three dimensional coordination of the β-Cd3(PO4)2 structure; (a) two successive layers parallel to the ab plane of the cations (Cd2, Cd4 and Cd9) and (Cd5, Cd6 and Cd8), (b) Cd2O5, Cd4O5 and Cd9O6 polyhedra forming a ring of eight polyhedra, (c) two pyramids (Cd5O5, Cd6O5) and a deformed octa­hedron (Cd8O6) arranged to share corners building the second layer, (d) first and second layer connected, (e) a zigzag chain composed of the two pyramids Cd1O5 and Cd3O5 and the Cd7O6 prism fills the large tunnels of the framework, (f) the sequence of the three pyramids Cd1O5, Cd5O5, Cd6O5 and the square-based prism Cd7O6.

Powder X-ray diffraction

The single crystal diffraction analysis and refinement of β-Cd3(PO4)2 produced high-quality crystallographic data, which were then used to run a profile matching with a Le Bail approach for X-ray powder analysis. This study leads to a very good match (Fig. 4[link]), confirming the unit-cell parameters and space-group symmetry of the compound. The obtained lattice parameters are a = 9.1861 (8) Å, b = 10.3349 (8) Å, c = 21.689 (2) Å, and β = 99.575 (3)°, in the monoclinic system, space group P21/n. This fact is corroborated by the good merit factors: Rp = 8.1%, Rwp = 11.7%, Rexp  = 8.5%, χ2 = 1.904.

[Figure 4]
Figure 4
Calculated and observed X-ray diffraction patterns for β-Cd3(PO4)2.

Fourier-transform infrared analysis

Fig. 5[link] presents the FTIR spectra of β-Cd3(PO4)2, displaying two distinct regions of bands that originate from the [PO4]3− groups. The first region, ranging from 1151 to 936 cm−1, correspond to the P—O fundamental vibrational modes, while the second region, spanning from 624 to 431 cm−1, indicates the bending modes of O—P—O. These two groups of bands exhibit similarities with those observed in the A3(PO4)2 family (Jin et al., 2014[Jin, K., Park, J., Lee, J., Yang, K. D., Pradhan, G. K., Sim, U., Jeong, D., Jang, H. L., Park, S., Kim, D., Sung, N. E., Kim, S. H., Han, S. & Nam, K. T. (2014). J. Am. Chem. Soc. 136, 7435-7443.]). Specifically, the bands located at 1051, 1026, 971, and 936 cm−1 in β-Cd3(PO4)2 correspond to the fundamental vibrational modes of the symmetric P—O stretching, while the bands at 624, 597, 570, 558, 544, 531, and 431 cm−1 are assigned to the bending modes of O—P—O. Table 1[link] summarizes the bands and their corresponding assignments.

Table 1
Infrared bands of β-Cd3(PO4)2 and their assignments

Band Assignment
431 PO4 v2 out of plane bending modes
531 PO4 v4 out of plane bending modes
544 PO4 v4 out of plane bending modes
558 PO4 v4 out of plane bending modes
570 PO4 v4 out of plane bending modes
597 PO4 v4 out of plane bending modes
624 PO4 v4 out of plane bending modes
936 The symmetric P—O stretching corresponds to the undamental vibrational mode v1
971 The symmetric P—O stretching corresponds to the fundamental vibrational mode v1
1026 The triple-degenerate asymmetric P—O stretching mode corresponds to the v3 fundamental vibrational mode
1051 The triple-degenerate asymmetric P—O stretching mode corresponds to the v3 fundamental vibrational mode
[Figure 5]
Figure 5
FT–IR spectra of β-Cd3(PO4)2.

Morphology of the powders

In Fig. 6[link], the morphology of β-Cd3(PO4)2 powders is depicted, showing particulate structures of a pulverized powder. The micrographic analysis indicates that the grains possess a well-defined shape. Furthermore, the EDX analysis confirms the purity and composition of the compound, which was also reported by Rajasri et al. (2019[Rajasri, S., Krishnakumar, B., Abilio, J. F., Sobral, N., Balachandran, S., Swaminathan, M. & Muthuvel, I. (2019). Mater. Today Proc., 15, 471-480.]), thereby verifying its high quality.

[Figure 6]
Figure 6
SEM images and EDX spectra of β-Cd3(PO4)2.

UV–Visible spectroscopy analysis.

UV–Visible absorbance spectra of the β-Cd3(PO4)2 compound is presented in Fig. 7[link]. The analysis was performed on a powder sample. An absorbance band is observed at 289 nm. The Kubelka–Munk analyses are required to determine the experimental band-gap energy. The band gap energy is the crossing point between the linear inclination of the absorption band and the energy axis. The estimated optical indirect band-gap energy is 3.85 eV. This energy value roughly places this phosphate in the class of semiconductors.

[Figure 7]
Figure 7
UV–Vis absorption spectra of β-Cd3(PO4)2. The inset shows the plot of (αhν)1/2 for determining the band-gap energy.

3. Database survey

The crystal structure of the tricadmium diorthophosphate, namely β-Cd3(PO4)2, was determined by Stephens (1967[Stephens, J. S. (1967). Doctor of Philosophy Thesis, McMaster University, Hamilton, Ontario (May, 1967).]) using X-ray diffraction data collected from Weissenberg photographs. Its corresponding high-temperature form crystallizes in the monoclinic system and presents structural similarities with the β-Mn3(PO4)2 graftonite type (Stephens & Calvo, 1969[Stephens, J. S. & Calvo, C. (1969). Can. J. Chem. 47, 2215-2225.]). In light of this literature, β-Cd3(PO4)2 adopts the monoclinic space group P21/c with the following cell parameters: a = 9.221 (1) Å, b = 10.335 (1) Å, c = 24.902 (5) Å, and β = 120.7 (2)° (Stephens, 1967[Stephens, J. S. (1967). Doctor of Philosophy Thesis, McMaster University, Hamilton, Ontario (May, 1967).]; see Table 2[link]). However, the crystal structure details are not readily available in the published articles. Furthermore, during our research on transition-metal-based phosphates, we have synthesized β-Cd3(PO4)2 crystals that crystallize in the monoclinic system with the lattice parameters a′ = 9.1895 Å, b′ = 10.3507 Å, c′ = 21.6887 Å, β′ = 99.64°, space group P21/n (see Table 2[link]). In fact, these parameters are related to those found by Stephens through the following basis transformation a′ = a, b′ = b and c′ = a + c. Although there is a relationship between the unit-cell parameters, it is very difficult to compare the two structural models due to the low quality of the Stephens (1967[Stephens, J. S. (1967). Doctor of Philosophy Thesis, McMaster University, Hamilton, Ontario (May, 1967).]) model. Thus, we cannot conclude that it is the same structure.

Table 2
Divalent cation-based orthophosphates [M3(PO4)2] summary crystallographic data (Å, °, Å3)

Compound Space group a b c β Z V Reference
Ca3(PO4)2 P21/a 12.89 (6) 27.28 (5) 15.22 (3) 126.2 (9) 24 4317.5 Mathew et al. (1977[Mathew, M., Schroeder, L. W., Dickens, B. & Brown, W. E. (1977). Solid State Commun. B33, 1325-1333.])
Cd3(PO4)2 P21/c 9.22 (4) 10.34 (9) 24.90 (2) 120.7 (1) 12 2030.0 Stephens (1967[Stephens, J. S. (1967). Doctor of Philosophy Thesis, McMaster University, Hamilton, Ontario (May, 1967).])
  P21/n 9.19 (7) 10.35 (1) 21.69 (9) 99.6 (2) 12 2033.8 Present work
Co3(PO4)2 P21/n 5.06 (8) 8.36 (2) 8.79 (4) 121.0 (1) 2 319.4 Anderson et al. (1975[Anderson, J. B., Kostiner, E., Miller, M. C. & Rea, J. R. (1975). J. Solid State Chem. 14, 372-377.])
Cr3(PO4)2 P21/n 4.97 (9) 9.50 (3) 6.48 (2) 91.4 (3) 2 305.6 Glaum et al. (2011[Glaum, R., Hammer, E., Hermes, W. & Pöttgen, R. (2011). Z. Anorg. Allg. Chem. 637, 1052-1061.])
Fe3(PO4)2 P21/a 10.44 (3) 4.79 (2) 6.03 (2) 91.0 (5) 2 301.3 Ericsson & Khangi (1988[Ericsson, T. & Khangi, F. (1988). Hyperfine Interact. 41, 783-786.])
  P21/n 8.88 (2) 11.17 (3) 6.15 (8) 99.4 (8) 4 601.0 Kostiner & Rea (1974[Kostiner, E. & Rea, J. R. (1974). Inorg. Chem. 13, 2876-2880.])
Mg3(PO4)2 P21/n 7.60 (7) 8.23 (1) 5.08 (1) 94.1 (5) 2 316.6 Nord & Kierkegaard (1968[Nord, A. G. & Kierkegaard, P. (1968). Acta Chem. Scand. 22, 1466-1474.])
  P21/m 7.605 (2) 8.233 (3) 5.080 (1) 94.19 (3) 2 317.2 Baykal et al. (1997[Baykal, A., Kizilyalli, M. & Kniep, R. (1997). Turk. J. Chem. 21, 394-400.])
  P21/n 10.25 (9) 4.72 (2) 5.92 (4) 90.9 (1) 2 287.0 Nord & Stefanidis (1983[Nord, A. G. & Stefanidis, T. (1983). Phys. Chem. Miner. 10, 10-15.])
Mn3(PO4)2 P21/c 8.94 (3) 10.04 (1) 24.12 (8) 120.8 (3) 12 1861.1 Stephens & Calvo (1969[Stephens, J. S. & Calvo, C. (1969). Can. J. Chem. 47, 2215-2225.])
  P21/c 8.80 (4) 11.45 (1) 6.25 (5) 99.0 (2) 4 621.9 Volkova et al. (2016[Volkova, O. S., Shvanskaya, L. V., Ovchenkov, E. A., Zvereva, E. A., Volkov, A. S., Chareev, D. A., Molla, K., Rahaman, B., Saha-Dasgupta, T. & Vasiliev, A. N. (2016). Inorg. Chem. 55, 10692-10700.])
  P21/c 8.92 (1) 9.15 (9) 8.66 (9) 111.7 (1) 4 657.2 Neher & Salguero (2017[Neher, G. & Salguero, T. T. (2017). Cryst. Growth Des. 17, 4864-4872.])
Ni3(PO4)2 P21/n 5.82 (6) 4.69 (2) 10.10 (5) 91.1 (3) 2 276.1 Escobal et al. (2005[Escobal, J., Pizarro, J. L., Mesa, J. L., Rojo, J. M., Bazan, B., Arriortua, M. I. & Rojo, T. (2005). J. Solid State Chem. 178, 2626-2634.])
  P21/c 8.70 (2) 11.12 (1) 6.11 (2) 100.0 (8) 4 581.7 Nord & Stefanidis (1983[Nord, A. G. & Stefanidis, T. (1983). Phys. Chem. Miner. 10, 10-15.])
Pb3(PO4)2 C2/c 13.81 (8) 5.69 (8) 9.43 (3) 102.4 (3) 4 723.5 Brixner et al. (1973[Brixner, L. H., Bierstedt, P. E., Jaep, W. F. & Barkley, J. R. (1973). Mater. Res. Bull. 8, 497-503.])
Sr3(PO4)2 R[\overline{3}]m 5.3901 (8) 5.3901 (8) 19.785 (5)   4 497.8 Sugiyama & Tokonami (1990[Sugiyama, K. & Tokonami, M. (1990). Miner. J. 15, 141-146. https://doi.org/10.2465/minerj.15.141])
Ba3(PO4)2 R[\overline{3}]m 5.6038 (7) 5.6038 (7) 21.000 (5)   4 571.1 Sugiyama & Tokonami (1990[Sugiyama, K. & Tokonami, M. (1990). Miner. J. 15, 141-146. https://doi.org/10.2465/minerj.15.141])
Zn3(PO4)2 P21/c 5.07 (2) 8.47 (3) 8.77 (2) 120.5 (5) 2 323.1 Calvo (1963[Calvo, C. (1963). J. Phys. Chem. Solids, 24, 141-149.]); Stephens & Calvo (1967[Stephens, J. S. & Calvo, C. (1967). Can. J. Chem. 45, 2303-2312.])
  C2/c 8.14 (7) 5.63 (3) 15.04 (9) 105.1 (8) 4 665.4 Calvo (1965[Calvo, C. (1965). Can. J. Chem. 43, 436-445.])
  P21/n 9.39 (8) 9.17 (1) 8.69 (3) 125.7 (3) 4 607.3 Stephens & Calvo (1969[Stephens, J. S. & Calvo, C. (1969). Can. J. Chem. 47, 2215-2225.])

It is important to note that the present structural model is obtained from the resolution and least-squares refinement of single crystal X-ray diffraction data (8280 reflections), measured with high precision. The low values of the reliability factors R and Rw (see Table 3[link]) show that this model is correct. Moreover, the precisions of the inter­atomic distances and angles calculated from the atomic positions are very satisfactory and the values are compatible with the P—O and Cd—O distances and the O—P—O and O—Cd—O angles given in the literature of this type of phosphate. In the recent model, the cadmium–oxygen (Cd—O) bonds vary between 2.1454 and 2.5935 Å. In contrast, Stephens' structure shows a more varied Cd—O bond length, ranging from 2.13 to 2.7 Å. Furthermore, the current structure portrays the phosphate tetra­hedra with regular geometries, wherein phospho­rus–oxygen (P—O) bond distances are consistently between 1.527 and 1.556 Å. Stephens' model, on the other hand, presents a wider P—O bond distance variation, from 1.44 to 1.63 Å. The irregularities observed in the Stephens' polyhedral units potentially stem from the aforementioned data resolution limitations of that study.

Table 3
Experimental details

Crystal data
Chemical formula Cd3(PO4)2
Mr 527.14
Crystal system, space group Monoclinic, P21/n
Temperature (K) 296
a, b, c (Å) 9.1895 (7), 10.3507 (8), 21.6887 (16)
β (°) 99.644 (3)
V3) 2033.8 (3)
Z 12
Radiation type Mo Kα
μ (mm−1) 9.81
Crystal size (mm) 0.31 × 0.27 × 0.22
 
Data collection
Diffractometer Bruker X8 APEX Diffractometer
Absorption correction Multi-scan (SADABS; Krause et al., 2015[Krause, L., Herbst-Irmer, R., Sheldrick, G. M. & Stalke, D. (2015). J. Appl. Cryst. 48, 3-10.])
Tmin, Tmax 0.544, 0.747
No. of measured, independent and observed [I > 2σ(I)] reflections 129694, 9851, 8280
Rint 0.047
(sin θ/λ)max−1) 0.833
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.023, 0.054, 1.07
No. of reflections 9851
No. of parameters 352
Δρmax, Δρmin (e Å−3) 1.60, −1.74
Computer programs: APEX3 and SAINT (Bruker, 2016[Bruker (2016). APEX3 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]), SHELXT2014/5 (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]), SHELXL2018/3 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]), ORTEP-3 for Windows (Farrugia, 2012[Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849-854. ]), DIAMOND (Brandenburg, 2006[Brandenburg, K. (2006). DIAMOND. Crystal Impact GbR, Bonn, Germany.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

The rich crystal chemistry of the 3d transition-metal (II) orthophosphates attracts scientists to study their physico-chemical properties. From the crystallographic point of view, the most commonly adopted symmetry for the M3(PO4)2 family is the monoclinic system, space group P21/c. Table 2[link] summarizes the crystallographic data for a selection of compounds belonging to this family. It appears from analysis of this table that the structural study of practically all phosphates belonging to this family has long been carried out, except Cr3(PO4)2. The latter phosphate crystal structure, constructed from CrO5, CrO6 and PO4 polyhedra, is closely related to the studied phosphate in the present work. However, a structural reinvestigation of some phosphates, such as Ni3(PO4)2 and Mn3(PO4)2, has been undertaken in recent years, as shown in Table 2[link].

4. Synthesis and crystallization

Single crystals of β-Cd3(PO4)2 were synthesized by a hydro­thermal process using the following protocol. In a Teflon beaker of 23 mL, cadmium nitrate (0.567 g, 99%) and phospho­ric acid (1.09 mL of a solution of 14.615 M) were mixed in the molar ratio Cd(NO3)2:H3PO4 = 3:2, and 12 mL of distilled water were added to the mix. The Teflon beaker was placed in the autoclave, carefully sealed, and heated at 473 K for two days. The resulting product constituted two single-crystal types with different shapes. Binocular observations allowed us to estimate the percentage of the two different crystal forms at 50% each. Single-crystal X-ray analysis revealed that the first one corresponds to the well-known compound Cd5(PO4)3OH (Hata et al., 1978[Hata, M., Okada, K., Iwai, S., Akao, M. & Aoki, H. (1978). Acta Cryst. B34, 3062-3064.]), a prism-shaped phosphate, while the second type, which is parallelepiped shaped, is the subject of the present work and was identified as β-Cd3(PO4)2.

The powder of the studied phosphate was synthesized by means of solid-state reaction carried out in air. Cadmium nitrate (99%), and di-ammonium hydrogen-phosphate (99%) were weighed at a molar ratio of 3:2 and ground thoroughly in an agate mortar. The mixture was pre-heated at 423 K, 623 K, and 823 K. The resulting powder was then ground thoroughly and heated to 1273 K for 24 h to obtain pure β-Cd3(PO4)2.

Experimental details

X-ray powder diffraction data were collected at room temperature using a Shimadzu diffractometer model LABXRD-6100, equipped with a secondary monochromator and Cu Kα radiation (λ = 1.54056 Å). The X-ray diffraction data were collected at 40 kV in the inter­val 10° ≤ 2θ ≤ 70° with a step of 0.04 in 2θ and a counting time of 1.2 s per step. The collected XRD pattern was fitted using JANA2006 software (Petříček et al., 2014[Petříček, V., Dušek, M. & Palatinus, L. (2014). Z. Kristallogr. 229, 345-352.]). The morphology and composition of the synthesized material were characterized using a JEOL JSM-IT 100 scanning electron microscope (SEM) equipped with an EDX at an accelerating voltage of 20 kV. Fourier-transform infrared spectroscopy (FTIR) was performed using a Bruker Platinum-ATR instrument. UV–Visible absorbance measurements were performed on powder samples using a JASCO instrument in the range of 190 to 900 nm at room temperature. The crystal structures were visualized using DIAMOND crystal and mol­ecular structure software (Bergerhoff et al., 1996[Bergerhoff, G., Berndt, M. & Brandenburg, K. (1996). J. Res. Natl Inst. Stand. Technol. 101, 221-225.]).

5. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3[link].

Supporting information


Computing details top

Tricadmium bis(orthophosphate) top
Crystal data top
Cd3(PO4)2F(000) = 2856
Mr = 527.14Dx = 5.165 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 9.1895 (7) ÅCell parameters from 9851 reflections
b = 10.3507 (8) Åθ = 2.2–36.3°
c = 21.6887 (16) ŵ = 9.81 mm1
β = 99.644 (3)°T = 296 K
V = 2033.8 (3) Å3Parallelepiped, colourless
Z = 120.31 × 0.27 × 0.22 mm
Data collection top
Bruker X8 APEX Diffractometer9851 independent reflections
Radiation source: fine-focus sealed tube8280 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.047
φ and ω scansθmax = 36.3°, θmin = 2.2°
Absorption correction: multi-scan
(SADABS; Krause et al., 2015)
h = 1515
Tmin = 0.544, Tmax = 0.747k = 1717
129694 measured reflectionsl = 3636
Refinement top
Refinement on F20 restraints
Least-squares matrix: fullPrimary atom site location: dual
R[F2 > 2σ(F2)] = 0.023Secondary atom site location: difference Fourier map
wR(F2) = 0.054 w = 1/[σ2(Fo2) + (0.0205P)2 + 4.3579P]
where P = (Fo2 + 2Fc2)/3
S = 1.07(Δ/σ)max = 0.004
9851 reflectionsΔρmax = 1.60 e Å3
352 parametersΔρmin = 1.74 e Å3
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Refinement. The crystal structure of β-Cd3(PO4)2 was investigated using single-crystal X-ray diffraction data collected at room temperature with a Bruker D8 Venture Super DUO Diffractometer equipped with a PHOTON100 CMOS area-detector and monochromatic MoKα radiation (λ=0.71073 Å). APEX3 (Bruker, APEX3 (Version 5.054), SAINT (Version 6.36A), SADABS. (Bruker, 2016) software was used for data reduction and the absorption correction was performed by multi-scan semi-empirical method using SADABS program (Krause, et al. 2015). The crystal structure was solved using dual space algorithm as implemented in SHELXT program (Sheldrick, 2015a), completed by a Difference Fourier map and refined by least-squares using SHELXL program (Sheldrick 2015b) integrated into the WinGX interface (Farrugia, 2012).

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Cd10.74691 (2)0.71080 (2)0.36476 (2)0.01178 (3)
Cd20.27909 (2)0.39633 (2)0.92293 (2)0.01251 (3)
Cd30.60228 (2)0.39417 (2)0.58439 (2)0.01124 (3)
Cd40.94569 (2)0.28838 (2)0.95686 (2)0.01149 (3)
Cd50.71202 (2)0.41020 (2)0.77990 (2)0.01002 (3)
Cd60.05148 (2)0.60385 (2)0.74786 (2)0.01157 (3)
Cd70.60491 (2)0.60229 (2)0.89221 (2)0.00988 (3)
Cd80.40399 (2)0.70425 (2)0.70409 (2)0.01088 (3)
Cd90.93970 (2)0.59251 (2)0.56014 (2)0.01049 (3)
P10.69824 (6)0.43486 (5)0.43995 (2)0.00739 (9)
P20.95135 (6)0.36168 (6)0.67096 (3)0.00825 (9)
P30.69971 (7)0.64250 (6)0.66858 (3)0.00801 (9)
P40.35072 (6)0.42713 (5)0.77938 (2)0.00705 (9)
P50.03383 (6)0.57903 (5)0.89456 (2)0.00714 (9)
P60.62768 (7)0.35381 (6)1.00079 (3)0.00835 (9)
O10.7195 (2)0.32411 (17)0.39518 (8)0.0153 (3)
O20.62835 (19)0.55464 (17)0.40326 (8)0.0120 (3)
O30.84808 (19)0.46875 (17)0.47901 (8)0.0132 (3)
O40.5870 (2)0.39020 (19)0.48128 (8)0.0158 (3)
O50.8179 (2)0.30534 (18)0.62739 (9)0.0161 (3)
O61.0338 (2)0.4652 (2)0.63983 (10)0.0255 (5)
O71.0579 (2)0.24766 (18)0.68907 (8)0.0166 (3)
O80.9105 (2)0.41803 (19)0.73139 (8)0.0175 (4)
O90.7346 (2)0.57633 (18)0.60939 (8)0.0153 (3)
O100.5947 (2)0.75733 (17)0.64955 (8)0.0149 (3)
O110.8400 (2)0.70048 (17)0.70769 (9)0.0154 (3)
O120.6177 (2)0.5506 (2)0.70596 (9)0.0204 (4)
O130.28310 (19)0.54515 (17)0.74156 (8)0.0117 (3)
O140.3730 (2)0.31593 (17)0.73519 (8)0.0138 (3)
O150.50013 (19)0.45790 (17)0.82041 (8)0.0125 (3)
O160.2369 (2)0.38617 (18)0.82065 (8)0.0138 (3)
O170.0602 (2)0.63773 (19)0.84925 (8)0.0163 (3)
O180.18533 (19)0.53473 (17)0.85947 (8)0.0128 (3)
O190.0598 (2)0.68256 (17)0.94219 (8)0.0136 (3)
O200.05089 (19)0.46386 (16)0.92864 (8)0.0117 (3)
O210.4881 (2)0.30043 (18)0.95967 (9)0.0168 (3)
O220.6649 (2)0.49060 (17)0.98153 (8)0.0156 (3)
O230.7475 (2)0.25479 (18)0.99447 (9)0.0186 (4)
O240.6119 (2)0.36004 (19)1.07107 (8)0.0167 (3)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cd10.01169 (7)0.01256 (7)0.01087 (6)0.00280 (6)0.00125 (5)0.00014 (5)
Cd20.01060 (7)0.01629 (8)0.00983 (6)0.00050 (6)0.00060 (5)0.00269 (5)
Cd30.00935 (7)0.01100 (7)0.01280 (7)0.00021 (5)0.00021 (5)0.00116 (5)
Cd40.01258 (7)0.01305 (7)0.00873 (6)0.00046 (6)0.00142 (5)0.00123 (5)
Cd50.01194 (7)0.00914 (7)0.00902 (6)0.00021 (5)0.00187 (5)0.00066 (5)
Cd60.00914 (7)0.01060 (7)0.01430 (7)0.00063 (5)0.00009 (5)0.00122 (5)
Cd70.01032 (7)0.01008 (7)0.00935 (6)0.00014 (5)0.00200 (5)0.00078 (5)
Cd80.01204 (7)0.01262 (7)0.00817 (6)0.00067 (5)0.00220 (5)0.00167 (5)
Cd90.01215 (7)0.01086 (7)0.00841 (6)0.00036 (5)0.00158 (5)0.00089 (5)
P10.0078 (2)0.0074 (2)0.0064 (2)0.00011 (18)0.00040 (17)0.00001 (17)
P20.0080 (2)0.0090 (2)0.0074 (2)0.00023 (18)0.00032 (17)0.00032 (18)
P30.0085 (2)0.0079 (2)0.0072 (2)0.00045 (18)0.00022 (17)0.00030 (17)
P40.0076 (2)0.0069 (2)0.00626 (19)0.00028 (18)0.00013 (17)0.00019 (17)
P50.0077 (2)0.0068 (2)0.0065 (2)0.00028 (18)0.00001 (17)0.00010 (17)
P60.0090 (2)0.0093 (2)0.0066 (2)0.00031 (18)0.00063 (18)0.00027 (18)
O10.0210 (9)0.0105 (7)0.0122 (7)0.0037 (6)0.0040 (6)0.0047 (6)
O20.0108 (7)0.0113 (7)0.0139 (7)0.0031 (6)0.0018 (6)0.0041 (6)
O30.0094 (7)0.0163 (8)0.0127 (7)0.0006 (6)0.0016 (6)0.0052 (6)
O40.0163 (8)0.0198 (9)0.0118 (7)0.0071 (7)0.0042 (6)0.0019 (6)
O50.0124 (8)0.0132 (8)0.0194 (8)0.0010 (6)0.0070 (6)0.0054 (6)
O60.0160 (9)0.0360 (12)0.0225 (9)0.0078 (8)0.0023 (7)0.0188 (9)
O70.0176 (9)0.0154 (8)0.0157 (8)0.0064 (7)0.0010 (6)0.0020 (6)
O80.0161 (9)0.0231 (9)0.0145 (7)0.0024 (7)0.0060 (6)0.0087 (7)
O90.0155 (8)0.0166 (8)0.0145 (7)0.0019 (7)0.0048 (6)0.0060 (6)
O100.0162 (8)0.0117 (8)0.0157 (7)0.0051 (6)0.0004 (6)0.0013 (6)
O110.0124 (8)0.0102 (8)0.0203 (8)0.0006 (6)0.0066 (6)0.0037 (6)
O120.0143 (9)0.0254 (10)0.0212 (9)0.0013 (7)0.0022 (7)0.0144 (8)
O130.0094 (7)0.0108 (7)0.0144 (7)0.0015 (6)0.0002 (6)0.0046 (6)
O140.0175 (8)0.0109 (7)0.0116 (7)0.0043 (6)0.0020 (6)0.0042 (6)
O150.0095 (7)0.0145 (8)0.0122 (7)0.0004 (6)0.0019 (6)0.0030 (6)
O160.0138 (8)0.0177 (8)0.0103 (7)0.0043 (6)0.0034 (6)0.0015 (6)
O170.0179 (9)0.0194 (9)0.0122 (7)0.0069 (7)0.0045 (6)0.0041 (6)
O180.0080 (7)0.0155 (8)0.0141 (7)0.0006 (6)0.0004 (6)0.0058 (6)
O190.0199 (9)0.0095 (7)0.0098 (6)0.0042 (6)0.0025 (6)0.0026 (6)
O200.0115 (7)0.0093 (7)0.0141 (7)0.0022 (6)0.0015 (6)0.0029 (6)
O210.0134 (8)0.0153 (8)0.0185 (8)0.0015 (6)0.0065 (6)0.0026 (7)
O220.0207 (9)0.0112 (8)0.0133 (7)0.0040 (6)0.0017 (6)0.0036 (6)
O230.0153 (9)0.0152 (8)0.0272 (9)0.0027 (7)0.0092 (7)0.0004 (7)
O240.0165 (9)0.0258 (10)0.0080 (6)0.0053 (7)0.0030 (6)0.0029 (6)
Geometric parameters (Å, º) top
Cd1—O22.1913 (17)Cd8—O132.2156 (17)
Cd1—O14i2.2782 (17)Cd8—O1i2.2783 (17)
Cd1—O17ii2.3068 (18)Cd8—O16xii2.2973 (18)
Cd1—O24iii2.3243 (18)Cd8—O7iii2.3285 (18)
Cd1—O7iv2.338 (2)Cd8—O102.3381 (19)
Cd2—O162.1896 (17)Cd8—O122.522 (2)
Cd2—O212.1900 (19)Cd9—O32.2248 (17)
Cd2—O202.2336 (18)Cd9—O62.2297 (19)
Cd2—O22v2.3602 (18)Cd9—O21iii2.3135 (19)
Cd2—O1vi2.3996 (18)Cd9—O92.3230 (18)
Cd3—O42.2176 (17)Cd9—O3iv2.3411 (18)
Cd3—O52.2409 (18)Cd9—O23iii2.550 (2)
Cd3—O2i2.2437 (17)P1—O31.5316 (18)
Cd3—O92.2598 (18)P1—O11.5358 (18)
Cd3—O19vii2.2818 (18)P1—O41.5388 (18)
Cd4—O232.1454 (19)P1—O21.5529 (17)
Cd4—O20viii2.1924 (17)P2—O61.533 (2)
Cd4—O4ix2.2702 (18)P2—O51.5327 (18)
Cd4—O19v2.2836 (17)P2—O81.5376 (18)
Cd4—O10x2.2978 (18)P2—O71.5417 (19)
Cd5—O122.2292 (18)P3—O121.5283 (19)
Cd5—O18viii2.2326 (17)P3—O91.5354 (18)
Cd5—O11x2.2486 (18)P3—O111.5409 (18)
Cd5—O82.2543 (18)P3—O101.5430 (18)
Cd5—O152.3196 (18)P4—O141.5334 (18)
Cd6—O172.2150 (18)P4—O151.5391 (18)
Cd6—O11xi2.2293 (18)P4—O131.5430 (17)
Cd6—O132.2396 (17)P4—O161.5451 (18)
Cd6—O14xii2.3131 (18)P5—O191.5348 (18)
Cd6—O8xi2.313 (2)P5—O171.5383 (18)
Cd7—O222.2441 (17)P5—O181.5404 (18)
Cd7—O152.2547 (17)P5—O201.5429 (17)
Cd7—O18viii2.2732 (17)P6—O231.527 (2)
Cd7—O5iii2.2808 (18)P6—O221.5311 (19)
Cd7—O24v2.2990 (19)P6—O211.5372 (19)
Cd7—O7iii2.5935 (19)P6—O241.5566 (18)
O2—Cd1—O14i94.64 (7)O15—Cd7—O7iii77.53 (6)
O2—Cd1—O17ii98.73 (7)O18viii—Cd7—O7iii112.89 (6)
O14i—Cd1—O17ii73.41 (6)O5iii—Cd7—O7iii60.05 (6)
O2—Cd1—O24iii121.70 (6)O24v—Cd7—O7iii72.69 (6)
O14i—Cd1—O24iii141.54 (7)O13—Cd8—O1i92.86 (7)
O17ii—Cd1—O24iii87.86 (7)O13—Cd8—O16xii113.40 (7)
O2—Cd1—O7iv142.93 (6)O1i—Cd8—O16xii73.32 (6)
O14i—Cd1—O7iv80.58 (7)O13—Cd8—O7iii77.26 (6)
O17ii—Cd1—O7iv114.60 (7)O1i—Cd8—O7iii158.96 (7)
O24iii—Cd1—O7iv77.21 (6)O16xii—Cd8—O7iii93.39 (6)
O16—Cd2—O21110.02 (7)O13—Cd8—O10145.55 (6)
O16—Cd2—O2093.60 (7)O1i—Cd8—O1081.31 (7)
O21—Cd2—O20153.63 (7)O16xii—Cd8—O1097.48 (6)
O16—Cd2—O22v152.72 (7)O7iii—Cd8—O10117.23 (7)
O21—Cd2—O22v81.75 (7)O13—Cd8—O1287.84 (6)
O20—Cd2—O22v82.22 (7)O1i—Cd8—O12101.36 (7)
O16—Cd2—O1vi72.91 (6)O16xii—Cd8—O12158.06 (6)
O21—Cd2—O1vi79.03 (7)O7iii—Cd8—O1296.82 (7)
O20—Cd2—O1vi97.73 (7)O10—Cd8—O1260.58 (6)
O22v—Cd2—O1vi134.32 (6)O3—Cd9—O6108.60 (8)
O4—Cd3—O5108.31 (7)O3—Cd9—O21iii118.11 (7)
O4—Cd3—O2i102.91 (7)O6—Cd9—O21iii127.43 (7)
O5—Cd3—O2i146.53 (7)O3—Cd9—O995.37 (6)
O4—Cd3—O9101.42 (7)O6—Cd9—O980.79 (7)
O5—Cd3—O980.78 (7)O21iii—Cd9—O9115.63 (7)
O2i—Cd3—O9104.80 (7)O3—Cd9—O3iv77.59 (7)
O4—Cd3—O19vii75.41 (6)O6—Cd9—O3iv83.26 (7)
O5—Cd3—O19vii79.23 (6)O21iii—Cd9—O3iv84.39 (7)
O2i—Cd3—O19vii97.58 (7)O9—Cd9—O3iv159.49 (7)
O9—Cd3—O19vii157.50 (7)O3—Cd9—O23iii82.85 (6)
O23—Cd4—O20viii133.04 (7)O6—Cd9—O23iii153.31 (7)
O23—Cd4—O4ix105.57 (7)O21iii—Cd9—O23iii59.54 (6)
O20viii—Cd4—O4ix118.55 (7)O9—Cd9—O23iii74.04 (6)
O23—Cd4—O19v86.54 (7)O3iv—Cd9—O23iii123.24 (6)
O20viii—Cd4—O19v90.31 (7)O3—P1—O1108.84 (10)
O4ix—Cd4—O19v74.37 (6)O3—P1—O4111.71 (10)
O23—Cd4—O10x110.78 (8)O1—P1—O4108.13 (11)
O20viii—Cd4—O10x80.80 (6)O3—P1—O2110.91 (10)
O4ix—Cd4—O10x96.33 (6)O1—P1—O2110.94 (10)
O19v—Cd4—O10x162.23 (7)O4—P1—O2106.28 (10)
O12—Cd5—O18viii104.06 (7)O6—P2—O5113.44 (11)
O12—Cd5—O11x130.59 (7)O6—P2—O8108.65 (12)
O18viii—Cd5—O11x122.38 (7)O5—P2—O8112.67 (11)
O12—Cd5—O883.60 (7)O6—P2—O7107.92 (12)
O18viii—Cd5—O894.01 (7)O5—P2—O7105.92 (10)
O11x—Cd5—O8107.18 (7)O8—P2—O7107.98 (11)
O12—Cd5—O1583.32 (7)O12—P3—O9110.88 (12)
O18viii—Cd5—O1581.78 (6)O12—P3—O11113.07 (11)
O11x—Cd5—O1587.22 (7)O9—P3—O11111.18 (11)
O8—Cd5—O15164.84 (7)O12—P3—O10106.22 (11)
O17—Cd6—O11xi101.60 (7)O9—P3—O10109.20 (10)
O17—Cd6—O13103.11 (7)O11—P3—O10105.98 (10)
O11xi—Cd6—O13150.83 (7)O14—P4—O15108.48 (10)
O17—Cd6—O14xii74.45 (6)O14—P4—O13110.24 (10)
O11xi—Cd6—O14xii81.67 (6)O15—P4—O13112.60 (10)
O13—Cd6—O14xii90.24 (7)O14—P4—O16109.29 (11)
O17—Cd6—O8xi102.19 (6)O15—P4—O16110.29 (10)
O11xi—Cd6—O8xi83.31 (7)O13—P4—O16105.89 (10)
O13—Cd6—O8xi106.17 (7)O19—P5—O17108.76 (11)
O14xii—Cd6—O8xi163.55 (7)O19—P5—O18108.10 (10)
O22—Cd7—O15105.64 (7)O17—P5—O18111.09 (10)
O22—Cd7—O18viii90.72 (7)O19—P5—O20109.87 (9)
O15—Cd7—O18viii82.34 (6)O17—P5—O20108.60 (11)
O22—Cd7—O5iii126.62 (7)O18—P5—O20110.39 (10)
O15—Cd7—O5iii126.31 (7)O23—P6—O22113.50 (11)
O18viii—Cd7—O5iii85.34 (7)O23—P6—O21104.52 (11)
O22—Cd7—O24v83.70 (7)O22—P6—O21112.15 (10)
O15—Cd7—O24v93.27 (7)O23—P6—O24107.62 (11)
O18viii—Cd7—O24v171.73 (7)O22—P6—O24106.90 (11)
O5iii—Cd7—O24v102.88 (7)O21—P6—O24112.17 (11)
O22—Cd7—O7iii156.36 (7)
Symmetry codes: (i) x+1, y+1, z+1; (ii) x+1/2, y+3/2, z1/2; (iii) x+3/2, y+1/2, z+3/2; (iv) x+2, y+1, z+1; (v) x+1, y+1, z+2; (vi) x1/2, y+1/2, z+1/2; (vii) x+1/2, y1/2, z+3/2; (viii) x+1, y, z; (ix) x+1/2, y+1/2, z+1/2; (x) x+3/2, y1/2, z+3/2; (xi) x1, y, z; (xii) x+1/2, y+1/2, z+3/2.
Infrared bands of β-Cd3(PO4)2 and their assignments top
BandAssignment
431PO4 v2 out of plane bending modes
531PO4 v4 out of plane bending modes
544PO4 v4 out of plane bending modes
558PO4 v4 out of plane bending modes
570PO4 v4 out of plane bending modes
597PO4 v4 out of plane bending modes
624PO4 v4 out of plane bending modes
936The symmetric P—O stretching corresponds to the fundamental vibrational mode v1
971The symmetric P—O stretching corresponds to the fundamental vibrational mode v1
1026The triple-degenerate asymmetric P—O stretching mode corresponds to the v3 fundamental vibrational mode
1051The triple-degenerate asymmetric P—O stretching mode corresponds to the v3 fundamental vibrational mode
Divalent cation-based orthophosphates [M3(PO4)2] summary crystallographic data (Å, °, Å3) top
CompoundSpace groupabcβZVReference
Ca3(PO4)2P21/a12.89 (6)27.28 (5)15.22 (3)126.2 (9)244317.5Mathew et al. (1977)
Cd3(PO4)2P21/c9.22 (4)10.34 (9)24.90 (2)120.7 (1)122030.0Stephens (1967)
P21/n9.19 (7)10.35 (1)21.69 (9)99.6 (2)122033.8Present work
Co3(PO4)2P21/n5.06 (8)8.36 (2)8.79 (4)121.0 (1)2319.4Anderson et al. (1975)
Cr3(PO4)2P21/n4.97 (9)9.50 (3)6.48 (2)91.4 (3)2305.6Glaum et al. (2011)
Fe3(PO4)2P21/a10.44 (3)4.79 (2)6.03 (2)91.0 (5)2301.3Ericsson & Khangi (1988)
P21/n8.88 (2)11.17 (3)6.15 (8)99.4 (8)4601.0Kostiner & Rea (1974)
Mg3(PO4)2P21/n7.60 (7)8.23 (1)5.08 (1)94.1 (5)2316.6Nord & Kierkegaard (1968)
P21/m7.605 (2)8.233 (3)5.080 (1)94.19 (3)2317.2Baykal et al. (1997)
P21/n10.25 (9)4.72 (2)5.92 (4)90.9 (1)2287.0Nord & Stefanidis (1983)
Mn3(PO4)2P21/c8.94 (3)10.04 (1)24.12 (8)120.8 (3)121861.1Stephens & Calvo (1969)
P21/c8.80 (4)11.45 (1)6.25 (5)99.0 (2)4621.9Volkova et al. (2016)
P21/c8.92 (1)9.15 (9)8.66 (9)111.7 (1)4657.2Neher & Salguero (2017)
Ni3(PO4)2P21/n5.82 (6)4.69 (2)10.10 (5)91.1 (3)2276.1Escobal et al. (2005)
P21/c8.70 (2)11.12 (1)6.11 (2)100.0 (8)4581.7Nord & Stefanidis (1983)
Pb3(PO4)2C2/c13.81 (8)5.69 (8)9.43 (3)102.4 (3)4723.5Brixner et al. (1973)
Sr3(PO4)2R3m5.3901 (8)5.3901 (8)19.785 (5)4497.8Sugiyama & Tokonami (1990)
Ba3(PO4)2R3m5.6038 (7)5.6038 (7)21.000 (5)4571.1Sugiyama & Tokonami (1990)
Zn3(PO4)2P21/c5.07 (2)8.47 (3)8.77 (2)120.5 (5)2323.1Calvo (1963); Stephens & Calvo (1967)
C2/c8.14 (7)5.63 (3)15.04 (9)105.1 (8)4665.4Calvo (1965)
P21/n9.39 (8)9.17 (1)8.69 (3)125.7 (3)4607.3Stephens & Calvo (1969)
 

Acknowledgements

The authors would like to express their sincere gratitude to the Faculty of Science, Mohammed V University in Rabat for providing the resources and facilities necessary for carrying out this research and to the Laboratory of Physico-Chemistry of Inorganic and Organic Materials (LPCMIO), Normal School Supérieure (ENS), Rabat, Morocco for the FTIR analysis and for the fruitful collaboration.

References

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