Surface crystallisation behaviour of invert calcium phosphate glasses doped with V2O5

The crystallisation behaviour of calcium phosphate glasses with molar ratios of [CaO]/[P 2 O 5 ]=1.2 and V 2 O 5 contents of 5-13 mol% is investigated The results indicate the complex crystallisation behaviour of these glasses, which depends on the V 2 O 5 content. The crystallisation of these glasses was detected on DTA (differential thermal analysis) curves as one or two successive exothermal peaks in the temperature interval T=650-850°C. The crystallisation temperature peak decreased with increasing V 2 O 5 content. α-Ca 2 P 2 O 7 was formed as the primary phase, while β-Ca 2 P 2 O 7 and VP 2 O 7 were formed as the secondary phases. The content of β-Ca 2 P 2 O 5 decreased with increasing V 2 O 5 content, while that of VP 2 O 7 increased. From DTA analysis on powdered glasses and micrographs of fracture surfaces of heat treated bulk glasses it was confirmed these glasses crystallise via surface crystallisation.