Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270102003049/br1357sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270102003049/br1357Isup2.hkl | |
Rietveld powder data file (CIF format) https://doi.org/10.1107/S0108270102003049/br1357Isup3.rtv |
The γ polymorph of NaGaO2 was synthesized by a solid-state reaction. The starting materials were Na2CO3 (99.7%, Baker) and Ga2O3 (99.99%, Aldrich). A mixture (ratio?) totalling 10 g was prepared by weighing Na2CO3 and Ga2O3 and mixing them into a paste with acetone in an agate mortar. The mixture was fired in an electric muffle furnace, whose temperature was controlled and measured. Initial firing was at 873–973 K for a few hours to expel CO2, followed by 6 d at 1323 K and quenching in ice to room temperature.
The positions of 37 resolvable peaks were input to the LSUCRI program for least-squares unit-cell refinement (Garvey, 1986). The starting set of cell parameters for the refinement was taken from the data reported by Grey et al. (1990) for the isostructural compound KGaO2. The close values observed for the full width at half-maximum (FWHM; 0.12° at 28.446°), corresponding to the 111 peak of Si, NBS 640BC, used as external standard, and that for the 231 peak, belonging to the sample (FWHM = 0.124° at 29.962°), indicate a high degree of crystallinity in the specimen. The powder diffraction data were refined by the Rietveld method, using the coordinates reported for KGaO2 as starting parameters for the refinement. A pseudo-Voigt function modified by Thompson et al. (1987) was chosen to generate the line shape of the diffraction peaks. The background was fitted to a polynomial refinable function. The following parameters were refined in the space group Pbca: zero point, scale factor, six background polynomial coefficients, unit-cell dimensions, half-width, pseudo-Voigt and asymmetry parameters for the peak shape, and positional and isotropic displacement parameters. The FULLPROF program for Rietveld refinement and pattern-matching analysis (unpublished) is a strongly modified version (by Juan Rodríguez-Carvajal) of that described by Wiles & Young (1987).
Data collection: DIFFRAC/AT (Siemens, 1993); cell refinement: LSUCRI (Garvey, 1986); data reduction: Please provide missing details; program(s) used to solve structure: Please provide missing details; program(s) used to refine structure: FULLPROF (unpublished); molecular graphics: ATOMS (Dowty, 1994); software used to prepare material for publication: ATOMS.
NaGaO2 | Z = 16 |
Mr = 124.71 | Cu Kα1, Cu Kα2 radiation, λ = 1.54056, 1.544 Å |
Orthorhombic, Pbca | T = 295 K |
a = 5.3145 (2) Å | white |
b = 10.6234 (5) Å | flat sheet, 20 × 20 mm |
c = 14.7782 (7) Å | Specimen preparation: Prepared at 1323 K |
V = 834.36 (7) Å3 |
Siemens D5000 diffractometer | Data collection mode: reflection |
Radiation source: sealed X-ray tube, Cu Kα | Scan method: step |
Graphite monochromator | 2θmin = 10°, 2θmax = 90°, 2θstep = 0.02° |
Specimen mounting: packed powder sample container |
Least-squares matrix: full with fixed elements per cycle | 4001 data points |
Rp = 0.12 | Profile function: 'pseudo-Voigt modified by Thompson et al. (1987)' |
Rwp = ? | 47 parameters |
Rexp = 0.11 | |
RBragg = 0.05 | Background function: polynomial |
R(F2) = 0.04 | Preferred orientation correction: none |
χ2 = 2.190 |
NaGaO2 | V = 834.36 (7) Å3 |
Mr = 124.71 | Z = 16 |
Orthorhombic, Pbca | Cu Kα1, Cu Kα2 radiation, λ = 1.54056, 1.544 Å |
a = 5.3145 (2) Å | T = 295 K |
b = 10.6234 (5) Å | flat sheet, 20 × 20 mm |
c = 14.7782 (7) Å |
Siemens D5000 diffractometer | Scan method: step |
Specimen mounting: packed powder sample container | 2θmin = 10°, 2θmax = 90°, 2θstep = 0.02° |
Data collection mode: reflection |
Rp = 0.12 | R(F2) = 0.04 |
Rwp = ? | χ2 = 2.190 |
Rexp = 0.11 | 4001 data points |
RBragg = 0.05 | 47 parameters |
x | y | z | Uiso*/Ueq | ||
Ga1 | 0.1957 (5) | 0.0245 (3) | 0.1874 (4) | 0.0065 (6) | |
Ga2 | 0.3085 (6) | 0.2767 (3) | 0.0618 (3) | 0.0065 (6) | |
Na1 | 0.717 (2) | 0.985 (1) | 0.066 (1) | 0.020 (1) | |
Na2 | 0.815 (2) | 0.273 (1) | 0.190 (1) | 0.020 (1) | |
O1 | 0.640 (3) | 0.274 (1) | 0.040 (1) | 0.005 (1) | |
O2 | 0.212 (2) | 0.442 (1) | 0.083 (1) | 0.005 (1) | |
O3 | 0.225 (2) | 0.194 (2) | 0.170 (1) | 0.005 (1) | |
O4 | 0.134 (3) | 0.481 (1) | 0.289 (1) | 0.005 (1) |
Ga1—O2 | 1.84 (2) | Na1—O1 | 2.39 (2) |
Ga1—O3 | 1.83 (2) | Na1—O2 | 2.33 (2) |
Ga1—O4 | 1.85 (2) | Na1—O2' | 2.34 (2) |
Ga1—O4' | 1.81 (2) | Na1—O4 | 2.29 (2) |
Ga2—O1 | 1.79 (2) | Na2—O1 | 2.40 (2) |
Ga2—O1' | 1.83 (2) | Na2—O3 | 2.35 (1) |
Ga2—O2 | 1.85 (2) | Na2—O3' | 2.29 (2) |
Ga2—O3 | 1.87 (2) | Na2—O4 | 2.43 (2) |
O2—Ga1—O3 | 109.1 (14) | O1—Na1—O2 | 99.6 (10) |
O2—Ga1—O4 | 107.0 (13) | O1—Na1—O2' | 98.3 (9) |
O2—Ga1—O4' | 116.0 (14) | O1—Na1—O4 | 91.2 (10) |
O3—Ga1—O4 | 110.8 (13) | O2—Na1—O2' | 99.1 (10) |
O3—Ga1—O4' | 109.1 (13) | O2—Na1—O4 | 153.3 (13) |
O4—Ga1—O4' | 104.7 (13) | O2'—Na1—O4 | 103.4 (10) |
O1—Ga2—O1' | 109.2 (13) | O1—Na2—O3 | 104.2 (10) |
O1—Ga2—O2 | 108.5 (12) | O1—Na2—O3' | 139.2 (13) |
O1—Ga2—O3 | 112.2 (13) | O1—Na2—O4 | 87.8 (10) |
O1'—Ga2—O2 | 106.5 (13) | O3—Na2—O3' | 100.2 (10) |
O1'—Ga2—O3 | 116.5 (14) | O3—Na2—O4 | 135.0 (10) |
O2—Ga2—O3 | 103.5 (13) | O3'—Na2—O4 | 97.6 (10) |
Experimental details
Crystal data | |
Chemical formula | NaGaO2 |
Mr | 124.71 |
Crystal system, space group | Orthorhombic, Pbca |
Temperature (K) | 295 |
a, b, c (Å) | 5.3145 (2), 10.6234 (5), 14.7782 (7) |
V (Å3) | 834.36 (7) |
Z | 16 |
Radiation type | Cu Kα1, Cu Kα2, λ = 1.54056, 1.544 Å |
Specimen shape, size (mm) | Flat sheet, 20 × 20 |
Data collection | |
Diffractometer | Siemens D5000 diffractometer |
Specimen mounting | Packed powder sample container |
Data collection mode | Reflection |
Scan method | Step |
2θ values (°) | 2θmin = 10 2θmax = 90 2θstep = 0.02 |
Refinement | |
R factors and goodness of fit | Rp = 0.12, Rwp = ?, Rexp = 0.11, RBragg = 0.05, R(F2) = 0.04, χ2 = 2.190 |
No. of data points | 4001 |
No. of parameters | 47 |
No. of restraints | ? |
Computer programs: DIFFRAC/AT (Siemens, 1993), LSUCRI (Garvey, 1986), Please provide missing details, FULLPROF (unpublished), ATOMS (Dowty, 1994), ATOMS.
Ga1—O2 | 1.84 (2) | Na1—O1 | 2.39 (2) |
Ga1—O3 | 1.83 (2) | Na1—O2 | 2.33 (2) |
Ga1—O4 | 1.85 (2) | Na1—O2' | 2.34 (2) |
Ga1—O4' | 1.81 (2) | Na1—O4 | 2.29 (2) |
Ga2—O1 | 1.79 (2) | Na2—O1 | 2.40 (2) |
Ga2—O1' | 1.83 (2) | Na2—O3 | 2.35 (1) |
Ga2—O2 | 1.85 (2) | Na2—O3' | 2.29 (2) |
Ga2—O3 | 1.87 (2) | Na2—O4 | 2.43 (2) |
NaGaO2 belongs to the group of tetrahedrally coordinated oxides with the general formula ABO2, where A is Li or Na and B is Al, Ga or Fe (B is Fe only when A is Na). These oxides are usually polymorphic and the polymorphs fall into two groups.
The first group is known as the low-temperature β phase, having the basic wurtzite structure, and the second group is the high-temperature γ phase, where the crystal structure presents the cations distributed over two different sets of available tetrahedral sites.
In addition to these β and γ polymorphic phases, a low-temperature and sometimes high-pressure α form occurs (West, 1975).
Vielhaber & Hoppe (1969) and Müller & Hoppe (1992) have reported crystal data for the β phase of NaGaO2, but no reports exist to date concerning the synthesis or crystal characterization of the γ phase of NaGaO2, which is reported here.