The title compound Fe-2(WO4)(3), being a metastable phase, is very difficult to prepare by a solid state synthesis route starting from the corresponding oxides. It has been prepared by a newly developed solution route starting from aqueous solutions of ferrous ammonium sulfate and sodium tungstate. The various process parameters were optimized to get a suitable precursor, which upon calcination at 500 degreesC for 4 h gave a well crystalline product. The product was characterized by powder XRD to have a monoclinic unit cell of Fe-2(WO4)(3). Its thermal stability was investigated by high-temperature XRD. It was found to decompose to FeWO4 and WO3 at 750degreesC. The typical monoclinic to orthorhombic phase transition, and in turn negative thermal expansion, were not observed. (C) 2003 Elsevier Science B.V. All rights reserved.