Vibrational characteristics and structure of heavy metal fluoride glasses containing thorium and zirconium

This paper reports a vibrational spectroscopic study of a series of glasses composed of Li-Ba-Th-Zr-fluoride in which Th4+ is progressively replaced by Zr4+. In these glasses, Zr4+ shows a more pronounced variation in coordination number than previously observed. Distinct infrared reflectance and polarized Raman bonds due to Th4+ polyhedra are present only in the glasses containing less than 10 mole% ZrF4. In the glasses containing 10 or more mole% ZrF4, Raman and infrared bands due to Zr4+ polyhedra dominate the vibrational spectra, even in glasses where the ThF4 concentration is greater than the ZrF4 concentration. The difference in structural behavior or the Th4+ polyhedra as compared to the Zr4+ polyhedra is believed to be due to the smaller electric field intensity of the Th4+ and to the relatively restricted ability of Th4+ to vary its coordination number in response to the availability of F1-