Domain Structure of WO3Single Crystals

Abstract

Transparent single crystals of W${\mathrm{O}}_3$, in the form of plates as large as 10 mm×10 mm, have been prepared by a sublimation method. The domain structure of these crystals was investigated from room temperature to 1350°C, and a new and peculiar domain structure was found between 740°C and 810°C. This domain structure is probably associated with the change in crystal structure from orthorhombic to tetragonal. Lattice parameters determined optically from measurements of the angle between extinction positions of two neighboring domains agreed well with those obtained by x-ray analysis. The shift in the absorption edge to the infrared at 740°C was observed to take place for light polarized in a direction perpendicular to the $c$ axis, but not for light polarized parallel to the $c$ axis.