Comparison of a laboratorial scale synthesized and a commercial yttria-tetragonal zirconia polycrystals ceramics submitted to microwave sintering

Conventional sintering techniques of yttria-tetragonal zirconia polycrystals (Y-TZP) ceramics have presented limitations regarding the sintering time and temperature, increasing the cost of the final dental and biomedical products. Herein, microwave sintering comes to be an interesting alternative by providing fast heating, high densification, and grain-size control. The aim of this study was to compare the effect of microwave sintering of Y-TZP dental ceramics prepared from a pre-sintered commercial block and produced from powders synthesized in a laboratorial scale by the precipitation route. The synthetized and commercial discs were submitted to microwave sintering at 1450°C and 1350°C for 15, 30, and 60 minutes. Densification, fracture toughness, grain size, and crystalline phase quantification of the sintered groups were evaluated. Both synthetized and commercial groups sintered at 1450°C for 15 and 30 minutes showed the higher densification results (98% TD). XRD quantitative phase analysis indicates that samples present 89% tetragonal and 11% cubic phases, except for the group prepared from coprecipitated powders sintered at 1450°C for 30 minutes, that presented 79% and 21% of tetragonal and cubic phases. The microwave sintering at 1450°C allows hardness and fracture toughness values comparable to conventional sintering.