PREPARATION AND THERMAL-DECOMPOSITION OF YTTRIUM HYDROXIDE FLUORIDES

The hydrothermal treatment of Y2O3 in KF solution at 400°C gave single phase of yttrium hydroxide fluorides, Y(OH)3-xFx (0.65 < x < 1.43). Rietveld refinements of X-ray powder intensity data were performed for these solid solution phases. The hexagonal UCl3 type system was retained over the whole range of x observed. All these solid solutions were thermally decomposed to oxide fluorides up to 500°C. Single phase of metastable cubic YOF and tetragonal YO1-XF1+2x were obtained at 450°C for the solid solution with x = 0.98 and x = 1.43, respectively. The interatomic distances of anions (OH-,F-), IR data, and dehydration temperature of x < 1 phases supported the existence of hydrogen bonds. © 1991 Academic Press, Inc.