Intergrowth Tungsten Bronze Structures of PrxWO3, Formed at 50 kbar: An HRTEM Study

Abstract

New praseodymium intergrowth tungsten bronzes, PrxWO3, of (n)-ITB structure type have been prepared by solid state reaction at P=50 kbar and T=1570 K. The ordered members n=2, 3, and 4 were identified by high-resolution transmission electron microscopy. The structure of (2)-ITB was deduced from an electron micrograph, and the unit cell parameters were determined from the X-ray powder data: a=10.17 Å, b=7.418 Å, and c=3.790 Å. The praseodymium content (0.04≤x≤0.1), corresponding to less than half-filled hexagonal tunnels in the ITB-structures, was found by combining electron diffraction and microanalysis studies of the same crystal fragments. An ordered superstructure, designated (2)5(3)3-ITB, was also observed.