Change of phase compositions in calcia stabilized zirconia ceramics using a boric acid additive

Dense calcia-stabilized zirconia (CSZ) ceramics were prepared by using a small amount of boric acid (H3BO3) as the sintering additive at the sintering temperature of 1700°C. The effect of H3BO3 content on the sintering behavior, the change of phase composition and mechanical properties of the CSZ ceramics were mainly investigated. The results showed that, due to the reaction between B2O3 and CaO, borate liquid was formed during the sintering, which promoted the the densification of CSZ ceramics. Meanwhile, the depletion of the CaO from the lattice of CSZ ceramics resulted in the phase transformation of ZrO2. The content of tetragonal ZrO2 phase increased with increasing the H3BO3 content. So the phase composition of CSZ ceramics could be well controlled by adjusting the amount of H3BO3. The bending strength and fracture toughness of the sintered CSZ ceramics also increased with increasing the H3BO3 content, namely the content of tetragonal ZrO2 phase, which had better mechanical properties, and the highest value reached 267 MPa and 3.35 MPa·m1/2, respectively.