Compounds having negative coefficient of thermal expansion (NTE) can be utilized for the synthesis of composites having tailored co-efficient of thermal expansion (CTE). Many compounds are known to exhibit NTE over a limited temperature range. However, due to anisotropy and very limited temperature window for this unusual thermal behavior, it becomes very difficult to exploit the NTE in actual applications. ZrW2O8 is a cubic compound known for its isotropic NTE. It is stable in a very narrow temperature range 1105-1257 °C and is metastable up to 777 °C. Metastable ZrW2O8 undergoes an order?disorder transformation at around 155 °C accompanied by a discontinuity in NTE. This discontinuity is undesirable for the structural stability of CTE tailored composites. Mo substituted ZrW2O8 powders with varying Mo substitution levels are synthesized by a hydrothermal route. The phase transformation and decomposition of the samples are characterized by high temperature X-ray diffraction and differential scanning calorimetery. Partial substitution of Mo in for W is shown to progressively suppress the order? disorder transformation to about 6 °C at the same time shifting the decomposition above 850 °C forZrW1.09Mo0.91O8.
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