Electrical conductivity of boron orthophosphate in presence of water

The electrical conductivity (sigma) of boron phosphate was measured using impedance spectroscopy. It was found to be dependent on the B/P ratio, calcination temperature and is strongly affected by the presence of water. High temperature calcined BPO4 exhibited water assisted conductivity, surpassing 10(-3) S cm(-1), which increased up to sigma > 10(-2) S cm(-1) with decrease of calcination temperature. H-1, P-31 and B-11 MAS NMR evidenced that in the latter case this is due to hydrolytic formation of substantial amounts of phosphoric acid, while in the former case only partial hydrolysis occurs. When calcined at high temperature, boron phosphate proved to be reasonably stable in water.