A new polymorph of ZrW2O8 prepared using nonhydrolytic sol-gel chemistry

A new polymorph of ZrW2O8, structurally related to trigonal ZrMo2O8, has be en prepared at low temperatures using nonhydrolytic sol-gel chemistry. Its identity was established by powder X-ray diffraction, energy dispersive X-r ay analysis, and extended X-ray absorption fine structure (EXAFS). This mat erial is denser than the previously reported cubic and orthorhombic forms o f ZrW2O8 and decomposes into the binary oxides on prolonged heating at 700 degrees C. An EXAFS investigation of the crystallization of "ZrW2O8" gels, prepared by nonhydrolytic methods, suggests that the coordination environme nts of the cations in the heat-treated gels evolve toward those found in th e new form of ZrW2O8 prior to the crystallization of this product.