Characterization of the barium salt of 12-tungstophosphoric acid by spectroscopic methods

Abstract

Amongst the investigated salts of tungstophosphoric acid (WPA), special attention has been paid to barium salt of WPA (BaHWPA), because of its different behavior in comparison with other WPA salts. In order to complete the characterization of this salt we performed IR, Raman and photoluminescent spectroscopy as well as conductivity measurements. The obtained spectra were compared with the spectra of other large-strong cation salts. A very wide photoluminescent spectrum of the investigated compound in the visible range, with an emission maximum at 630 nm was recorded. There are some indications that this photoluminescence effect arose from a phase transformation at about 60°C, caused by the reversible reduction of tungsten ion (W 6+ + e ⇔ W 5+ ). This phase transformation of BaHWPA has already been observed in previous dielectric studies. Specific structural characteristics of BaHWPA affect the mechanism of proton conductivity.