Phase Behaviors of the ZrMo2-xWxO8 (x = 0.2-2.0) System and the Preparation of an Mo-Rich Cubic Phase

• Published in: European Journal of Inorganic Chemistry 2005, Vol.2005 (22), p.4521-4526
• Main Authors: Huang, Ling, Xiao, Qiu-guo, Ma, Hui, Li, Guo-bao, Liao, Fu-hui, Qi, Chuan-min, Zhao, Xin-hua
• Format: Review
• Language: English
• Subjects: Calorimetry; Materials science; Phase diagrams; Phase transitions; Zirconium
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.200500487

The phase behaviors of ZrMo2–xWxO8 (x = 0.2 to 2.0) solid solutions have been studied systematically by variable‐temperature X‐ray diffraction (XRD) and differential scanning calorimetric (DSC) techniques. A low‐temperature (LT) orthorhombic ZrMo2–xWxO8 (x = 0.2–2.0) phase is formed by dehydration of the precursors ZrMo2–xWxO7(OH)2(H2O)2 (x = 0.2–2.0) within a temperature range from 124 to 203 °C. Among them, the orthorhombic ZrMo2–xWxO8 solid solutions are able to convert further into metastable cubic phases within an x‐dependent temperature range from 502 to 552 °C; the trigonal phases become dominant at higher temperature for Mo‐rich solid solutions. However, no trigonal phases are formed in the high‐temperature region for W‐rich solid solutions. The absence of decomposition of ZrMo2–xWxO8 (x = 0.2 to 1.6) solid solutions up to 800 °C indicates that the molybdenum substitution leads to a remarkable improvement of the thermal stability in comparison with ZrW2O8. Based on the phase behaviors reported in this paper, an approach for the preparation of cubic Mo‐rich solid solutions ZrMo2–xWxO8 with attractive negative thermal expansion (NTE) properties is demonstrated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)