Influence of fabrication method on the structure and thermal expansion property of ZrWMoO₈ and its composites

We report the preparation of ZrWMoO₈ and its composites with near zero thermal expansion property using in situ solid state reaction or co-precipitation route. The aim of this study is to compare the influence of the fabrication method on the structure and thermal expansion of the products. The composition of the obtained powders was characterized by X-ray diffraction (XRD) and thermal expansion property was investigated by Thermomechanical Analysis (TMA), respectively. The results indicate that the room temperature structure of ZrWMoO₈ depends on the preparation method, and the structure can be indexed either as α-ZrW₂O₈ structure for in situ solid state reaction or as β-ZrW₂O₈ structure for co-precipitation route. The participation of the water in the reaction process was speculated to be the reason for the difference structure. However, no matter which structure ZrWMoO₈ adopted, it exhibits excellent negative thermal expansion property and can be utilized to decrease the thermal expansion of ZrO₂. The only difference is that the CTE curves of ZrO₂ composites with ZrWMoO₈ adopting α-ZrW₂O₈ structure have a discontinuity at about 150 °C due to the α–β phase transition while the other curves are linear.