Evolution of pressure-amorphized zirconium tungstate upon annealing

• Published in: Journal of non-crystalline solids 2009-11, Vol.355 (45), p.2289-2294
• Main Authors: Ravindran, T.R., Arora, A.K., Sastry, V.S., Sahu, P.Ch
• Format: Article
• Language: English
• Subjects: Ceramics; Condensed matter: structure, mechanical and thermal properties; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Glass transitions; Optical spectroscopy; Phonons; Physics; Raman scattering; Raman spectroscopy; Short-range order; Specific phase transitions; Structure; X-ray diffraction
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2009.07.019

Zirconium tungstate Zr(WO 4) 2 exhibits irreversible amorphization at high pressure. Upon heating, the pressure-amorphized phase transforms into different phase/phases depending on the pressure applied during heating. Transformation of pressure-amorphized samples to metastable cubic phase during isochronal annealing at ambient pressure is investigated using X-ray diffraction and Raman spectroscopy. Though the X-ray diffraction and Raman spectra show only monotonic changes up to 850 K in the amorphous state, the sample exhibits dramatic changes in the color from gray to black to white. The relaxation of the amorphous phase during annealing suggests gradual irreversible volume increase by about 6%, whereas the tungstate tetrahedra are found to shrink. Crystallization to cubic phase at 900 K is accompanied by a large increase in the sample volume. The specific volumes of the amorphous phases obtained from cycling the samples to different pressures suggest the possibility of polyamorphism in this system.