Sr1/2Ce5/14□1/7WO4: a new modulated ternary scheelite compound

Abstract

For the first time, a ternary tetragonal scheelite structure tungstate with strontium and cerium cations, (Sr,Ce)WO4, was synthesized. As much as 35% Ce could be inserted into the structure, leaving 1\over 7 of the (Sr,Ce) cation sites vacant. Partial ordering of Sr and Ce, with atomic displacements, were shown by high-resolution electron microscopy. Two-dimensional incommensurate modulations occur in this material, in small domains 20 nm in size. The band gap of this compound is significantly lower than the band gap of SrWO4and this was related to the distortions of WO4and (Sr,Ce)O8polyhedra. The band gap value of 3.2 eV makes Sr1/2Ce5/14□1/7WO4a promising candidate for violet luminescence.