Microwave Sintering of Yttria-Stabilised Zirconia

Abstract

3mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) ceramic is widely used as engineering material owing to its great strength. Recently, 3Y-TZP ceramic is receiving great response in dental restoration due to its bio-compatible properties and aesthetic appearance. To achieve high bulk density, high sintering temperature (> 1500 °C), low firing rate (10 °C/min) coupled with long dwelling period (2 hours) are required in conventional sintering (CS) to fabricate 3Y-TZP ceramic which resulted in high energy consumption. Therefore, non-conventional sintering technique with low energy consumption such as microwave (MW) sintering is worth to explore as almost 100 % of electromagnetic energy is converted into heat largely within the sample itself. The commercial available 3Y-TZP powder was MW fired from 1200 °C to 1400 °C. The 3Y-TZP ceramics fabricated via MW sintering was compared with those CS samples by assessing the densification and mechanical properties of the ceramics. It was revealed that the total sintering time was reduced by 75 % for microwave-sintered 3Y-TZP ceramics to achieve relative density of ∼ 98 %, Young’s modulus of ∼ 205 GPa, and Vicker’s hardness of 14.15 GPa at low sintering temperature (1200 °C) as compared to CS ceramic that required temperature above 1250 °C. However, the properties of both MW and CS-sintered ceramics are comparable when the sintering temperature exceeds 1250 °C.