Influence of Temperature on the Order-Disorder Transition in Gd₂Zr₂O₇

Abstract:

Chemical co-precipitation method was used to prepare Gd₂Zr₂O₇ powders. The powders were then heated in air at 1500°C, 1510°C, 1525°C, 1530°C, 1550°C, 1575°C, 1600°C for 5 h, and 1575°C, 1600°C for 10 h, respectively. The samples after heat treatment were characterized by X-ray diffraction and Raman spectroscopy. X-ray diffraction patterns reveal that order-disorder transition of Gd₂Zr₂O₇ occurs between 1550°C and 1575°C. Prior to the transition, the relative intensity of peaks corresponding to the super-lattice of pyrochlores increases with the increasing temperature. On the other hand, Raman spectra give an inconsistent result from the X-ray diffraction data. No appreciable difference can be observed for all the samples though with peaks broadening as temperature increases. The spectra of the samples indicated as fluorite structure in X-ray diffraction patterns appear with six resolvable peaks which is quite different from the spectrum of ideal fluorite structure.

• Periodical: Key Engineering Materials (Volume 697)
• Pages: 386-389
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.697.386
• Online since: July 2016
• Authors: Jing Lin Shi, Zhi Xue Qu*, Qun Wang
• Keywords: Fluorite, Order-Disorder Transition, Pyrochlore

References

[1] Minervini L, Grimes R W, Sickafus K E. Disorder in pyrochlore oxides, J. Am. Ceram Soc. 83 (2000) 1873-1878.

DOI: 10.1111/j.1151-2916.2000.tb01484.x

[2] Stanek C R, Minervini L, Grimes R W. Nonstoichiometry in A2B2O7 pyrochlores, J. Am. Ceram. Soc. 85 (2002) 2792-2798.

DOI: 10.1111/j.1151-2916.2002.tb00530.x

[3] Zhixue Qu, Chunlei Wan, Wei Pan. Thermal expansion and defect chemistry of MgO-doped Sm2Zr2O7. Chem. Mater. 19 (2007) 4913-4918.

DOI: 10.1021/cm071615z

[4] Tabira Y, Withers R L. Structure and crystal chemistry as a function of composition across the wide range nonstoichiometric (1-ε) ZrO2·εSmO1. 5, 0. 38 <ε< 0. 55, oxide pyrochlore system, J Solid State Chem. 148 (1999) 205-214.

DOI: 10.1006/jssc.1999.8433

[5] McCauley R A. Structural characteristics of pyrochlore formation, J. Appl Phys, 51 (1980) 290-294.

[6] Tabira Y, Withers R L, Minervini L. Systematic structural change in selected rare earth oxide pyrochlores as determined by wide-angle CBED and a comparison with the results of atomistic computer simulation. J Solid State Chem. 153 (2000)16-25.

DOI: 10.1006/jssc.2000.8712

[7] Kostorz G, Herman H, Alper A M. Phase diagrams in advanced Ceramics. M. Elsevier, (1995).

[8] Zdeňka Čermáková, Petr Bezdička, Ivan Němec, anka Hradilová. Naturally irradiated fluorite as a historic violet pigment: Raman spectroscopic and X-ray diffraction study. J. Raman Spectrosc. 46 (2015) 236–243.

DOI: 10.1002/jrs.4627

[9] Zhixue Qu. Defect chemistry and thermophysical properties of rare-earth oxide ceramics for thermal barrier coating applications. Beijing: Tsinghua University, (2009).