Order and twining in Sb2W0.75Mo0.25O6

Synthesis, X-rays, TEM and HREM studies of the composition <f>x=0.25</f> of the solid solution Sb2W<f>1−x</f>Mo<f>x</f>O6 are reported. The phase crystallises in the monoclinic system, space group C2 and the cell parameters of its average structure are <f>a=11.1296(6)</f> A˚, <f>b=9.8868(9)</f> A˚, <f>a=18.501(2)</f> A˚ and <f>β=96.951(9)</f>°. Mo and W atoms are ordered in the <f>1/3</f> ratio. Twining and extended defects have been studied by TEM and HREM. [Copyright &y& Elsevier]