The common preparation method of zirconia ceramics is to obtain zirconia ceramic blocks from zirconia powder through processes such as molding and pre-sintering, and then perform secondary sintering to improve its density and mechanics. strength. During the sintering process, the organic solvents, binders and other components contained in the molded body are volatilized and decomposed. The atoms in the ceramic particles obtain enough energy to migrate. The powder particles in the ceramics can bond with each other to form a sintering neck, thereby making the crystal The grains grow larger, the grain boundaries shrink, the porosity decreases, the volume decreases and the density increases, finally forming a dense and hard all-ceramic zirconia ceramic tooth structure.
(1) Initial stage of sintering
At this stage, the zirconia ceramic particles begin to bond, and the contact points between the particles gradually form a sintering neck through processes such as nucleation and grain growth, but the shape of the particles and The internal grains have not changed significantly. At this time, the linear shrinkage rate of ceramics is generally about 2 to 3%, and there is no obvious densification process.
(2) Middle stage of sintering
When the powder particles are in the middle stage of sintering, as the sintering neck gradually grows, the atoms inside it accelerate and migrate toward the bonding surface between particles, causing the distance between particles to continue. shrink, eventually forming a continuous network of pores. During the entire process, the size of the grains continues to increase, the density and strength of the particles are improved, and the linear shrinkage of the entire molded body exceeds 10%.
(3) Late stage of sintering
When the sintering behavior reaches the later stage, the pores between particles continue to spheroidize and shrink, and most of the pores are separated to form closed pores. The materials on the grain boundaries continue to migrate to the pores. Prompt the grains to continue growing. At this stage, the pores are reduced, the shrinkage rate is further reduced, and the ceramic density is very high.
