Aqueous sol–gel processing of precursor oxides for ZrW2O8 synthesis

This paper describes the synthesis of ZrW2O8 by the use of an aqueous citrate-gel method in order to prepare a fine, pure and homogeneous oxide mixture suitable for ceramic processing. The thermal expansion coefficient thus obtained for α-ZrW2O8 is −10.6 × 10−6 °C−1 (50–125 °C) whereas for the β-ZrW2O8 a value of −3.2 × 10−6 °C−1 (200–300 °C) is obtained. The advantages of the use of a sol–gel method is expressed in the very homogeneous end-products. The paper describes crystallographic data, morphological structure and the thermal expansion properties of the ZrW2O8 material. Moreover, photoluminescence and photochromic properties specific to the precursor gel are described and analyzed. These effects support our views that the precursors show homogeneity up to nanometer level.