Sintering, microstructure and hardness of Y-TZP- 64S bioglass ceramics

Abstract

3mol% yttria-partially stabilized zirconia (Y-TZP) powder and a sol-gel derived CaO- P2O5- SiO2 (64S) bioglass, were used to produce Y-TZP- 64S slip cast compacts. The compacts with 10.5 and 19.9vol% 64S were sintered at different temperatures up to 1500°C using 5 and 10°C/min heating/cooling rates. The densification behaviour, crystalline phase formation and zirconia grain growth were investigated as a function of sintering temperature and 64S glass content. Ca3(PO4)2 along with SiO2 as a major phase were obtained from thermal decomposition of the 64S glass at 950–1500°C. Both 64S additions, 10.5 and 19.9vol%, promoted the sintering process at a lower temperature with respect to Y-TZP (1500°C); the SiO2 phase markedly increased the Y-TZP solid state sintering rate at the intermediate stage. The rapidly cooling at 10°C/min inhibited the t-m transformation of Y-TZP and markedly reduced that of Y-TZP- 64S at 1300–1500°C. Sintered Y-TZP with 10.5vol% 64S, nearly fully densified at 1300–1400°C, was constituted by polygonal ZrSiO4 particles and elongated Ca2P2O7 particles uniformly distributed in the tetragonal zirconia fine grain matrix. This ceramic exhibited similar hardness to that of Y-TZP sintered at 1500°C; the in situ formation of calcium phosphate will have the potential to improve the Y-TZP biological properties without significantly affecting its hardness.