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Phase Behaviors of the ZrMo 2– x W x O 8 ( x = 0.2–2.0) System and the Preparation of an Mo‐Rich Cubic Phase
Author(s) -
Huang Ling,
Xiao Qiuguo,
Ma Hui,
Li Guobao,
Liao Fuhui,
Qi Chuanmin,
Zhao Xinhua
Publication year - 2005
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200500487
Subject(s) - solid solution , chemistry , orthorhombic crystal system , crystallography , atmospheric temperature range , phase (matter) , x ray crystallography , differential scanning calorimetry , thermal decomposition , negative thermal expansion , molybdenum , metastability , analytical chemistry (journal) , thermal expansion , diffraction , crystal structure , thermodynamics , inorganic chemistry , physics , organic chemistry , chromatography , optics
The phase behaviors of ZrMo 2– x W x O 8 ( 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 ZrMo 2– x W x O 8 ( x = 0.2–2.0) phase is formed by dehydration of the precursors ZrMo 2– x W x O 7 (OH) 2 (H 2 O) 2 ( x = 0.2–2.0) within a temperature range from 124 to 203 °C. Among them, the orthorhombic ZrMo 2– x W x O 8 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 ZrMo 2– x W x O 8 ( 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 ZrW 2 O 8 . Based on the phase behaviors reported in this paper, an approach for the preparation of cubic Mo‐rich solid solutions ZrMo 2– x W x O 8 with attractive negative thermal expansion (NTE) properties is demonstrated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)