Effect of Heat Treatment Process on ZrW₂O₈ Synthesis by Hydrothermal Method

The negative thermal expansion Zr W₂O₈ materials were prepared by hydrothermal method. The effects of calcination temperature and cooling methods on the synthesized products were investigated. The results show that, the ZrW₂O₈ can be synthesized at 500-700 ℃, and the crystallinity of the product is the highest when the temperature is at 600 ℃. When the temperature rises to 800 ℃, the Zr W₂O₈ is decomposed seriously. The crystallinity of the calcined powder water cooling after is the highest, the crystallinity after furnace cooling is the second, and the crystallinity after air cooling is the lowest. The highest crystallinity is obtained when The precursor is calcined at 600 ℃ for 6 h after water cooling. The shape of powder is long strip and needle shape.