Minimization of absorption contrast for accurate amorphous phase quantification: application to ZrO₂ nanoparticles

Monoclinic and tetragonal zirconia samples were characterized by X-ray diffraction, pycnometry, thermogravimetric analysis (TGA), Fourier transform (FT) IR and mass (MS) spectroscopies, and scanning and transmission electron (TEM) microscopies. The results show, for the particular case of a tetragonal zirconia sample, an X-ray-undetected subproduct identified as an amorphous organic phase by FTIR-ATR (attenuated total reflection) and TGA-MS. The observations by TEM allowed this amorphous phase to be localized on the surface as a shell coating the nanoparticles. Moreover, this amorphous phase was quantified by Rietveld refinement via the addition of an internal silicon standard. Because zirconia and silicon have different linear absorption coefficients, the microabsorption effect was minimized by using small particle sizes. The amorphous phase was calculated to constitute 11.4 (30)% of the initial mass before Brindley correction and 10.6 (30)% of the initial mass after Brindley correction. The closeness of these values shows that the contribution of the Brindley correction can be neglected if precautions are taken on the microabsorption effect. This work has also highlighted the importance of thoroughly characterizing commercial products, which are not necessarily pure. Indeed, the presence of impurities could become a non-negligible parameter for physical and chemical properties studies related to commercial materials.

Computing details

For all compounds, data collection: Diffrac Plus Raw; cell refinement: Jana2006 (Petricek et al., 2006).

(monoclinic_zirconia) Zirconium Oxide

Crystal data

O2Zr	β = 99.215 (2)°
Monoclinic, P21/c	V = 140.74 (1) Å^3
a = 5.1477 (1) Å	Z = 4
b = 5.2096 (2) Å	Cu Kα1 radiation
c = 5.3164 (2) Å	T = 298 K

Data collection

Bragg-Brentano geometry diffractometer	2θmin = 20°, 2θmax = 100°
Radiation source: X-ray tube

Refinement

Rp = 8.7	R(F) = 1.37
Rwp = 11.5	Profile function: Lorenztian
RBragg = 1.4	Background function: Legendre polynomial

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.068 (1)	0.329 (1)	0.342 (1)	0.014 (2)
O2	0.449 (1)	0.7599 (8)	0.478 (1)	0.017 (3)
Zr1	0.2753 (2)	0.0399 (1)	0.2091 (2)	0.0045 (3)

(tetragonal_zirconia) Zirconium Oxide tetragonal

Crystal data

O1.985Y0.03Zr0.97	V = 67.73 (1) Å^3
Tetragonal, P42/nmcS	Z = 2
a = 3.6244 (3) Å	Cu Kα1 radiation
c = 5.156 (1) Å	T = 298 K

Data collection

Bragg-Brentano geometry diffractometer	2θmin = 20°, 2θmax = 100°
Radiation source: X-ray tube

Refinement

Rp = 9.8	R(F) = 2.98
Rwp = 13.1	Profile function: Lorenztian
RBragg = 3.0	Background function: Legendre polynomial

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
O	0.25	0.25	0.039 (1)	0.013 (1)	0.25
Zr	0.75	0.25	0.75	0.0061 (3)	0.125

(tetragonal_zirconia_annealed) Zirconium Oxide tetragonal

Crystal data

O1.985Y0.03Zr0.97	V = 67.43 (1) Å^3
Tetragonal, P42/nmcS	Z = 2
a = 3.6132 (1) Å	Cu Kα1 radiation
c = 5.1649 (2) Å	T = 298 K

Data collection

Bragg-Brentano geometry diffractometer	2θmin = 20°, 2θmax = 100°
Radiation source: X-ray tube

Refinement

Rp = 9.9	R(F) = 2.98
Rwp = 13.0	Profile function: Lorenztian
RBragg = 2.5	Background function: Legendre polynomial

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
O	0.25	0.25	0.039 (1)	0.014 (1)	0.25
Zr	0.75	0.25	0.75	0.0072 (3)	0.125