Study of phase equilibria in system BaO-B2O3 from 32 to 67Â mol% B2O3

We have studied phase equilibria of the binary system BaO-B2O3 on 28 samples from 32 to 67 mol% B2O3 by both the oscillation method of phase analysis (OPA) and thermal analysis. The temperature and melting type of compounds are defined more exactly. The existence of metastable phase of barium diborate: β-BaO·2B2O3 that is melting congruently is found. Besides, the existence of metastable phase 2BaO·3B2O3 that is melting incongruently and has boundary of low temperature stability is found. It is shown that the composition of crystallized stable and metastable phases and compounds depend on thermal prehistory of samples.