Boron Phosphate: Preparation in Aqueous Medium; Physical and Chemical Characterization

Heating equimolar amounts of pure phosphoric and boric acids in aqueous solution yields, at 130°, a solid boron phosphate of the composition R = P2O5/B2O3 = 1:1.71. Increasing the calcination temperature to 575° increases R to 1:1.29 due to evaporation of boron-values. Further heating to 850° causes no additional weight losses. The specific surface decreases monotonically with the calcination temperature, from 7.4 to 0.5 m2/g. X-ray diffraction data indicate that up to 10 min heating at 800°, increased calcination temperature causes a monotonic decrease in the unit cell dimensions, while prolonged heating (48 h) at this temperature reverses this trend.