INVESTIGATION OF DISPERSED PARTICLE-HARDENED ZIRCONIUM PORCELAIN

Porcelains were prepared by using kaolin clay, potassium feldspar, and quartz as the raw materials, and ZrO2 as a reinforcing material. This study investigated the effects of the amount of ZrO2, the firing temperature, and the holding time on the porcelain bending strengths and fracture toughness values, and compared the reinforcing effects of two types of ZrO2. The results show that the effect of the two types of ZrO2 (pure ZrO2 and Y2O3-stabilized ZrO2) on porcelain reinforcement were similar and that the optimal porcelain reinforcement was obtained with a ZrO2 content of 6 wt.%, firing temperature of 1300 ?, and holding time of 30 min. The bending strength increased from (58 ± 6) MPa to (89 ± 8) MPa (pure ZrO2) and (87 ± 8) MPa (Y2O3- stabilized ZrO2), with the respective growth rates reaching 62 and 58 %. Radial stress was generated in the matrix during the cooling process because of the difference between the thermal expansion coefficients of ZrO2 particles and the matrix.
This increased the porcelain strength. The phase transformation of ZrO2 improved the fracture toughness of the porcelain, but had little effect on reinforcement of the porcelain.