The influence of heating rate on two step sintering of advanced ceramic materials

Recently, there has been growing interest in new technologies and procedures to improve the microstructure of advanced ceramic materials. One of the most commonly used sintering methods is Two step sintering (TSS), Rapid rate sintering (RRS) and Spark plasma sintering (SPS). Within the framework of this bachelor thesis number of experiments were carried out for the research of the microstructure interconnecting the Two step sintering with the Rapid rate sintering and non-preassure Spark plasma sintering. The aim of this work was to determine the influence of the heating rate on the size of final relative density and the average grain size for ceramic materials based on ZrO2. The results of the study show that occurrence of the „core-shell“ structure on the ZrO2 doped by 3 mol.% Y2O3 (TZ-3Y) tend to production of non-homogenous microstructure with a fully compacted surface and a porous center. In the case of ZrO2 doped by 8 mol.% Y2O3 (TZ-8Y) this structure was detected only in several cases at higher heating rates. An the same time it was found that the final relative density decreases with increasing heating rate. Using cubic ZrO2 with larger grain size (TZ-8YSB), the „core-shell“ structure did not appear, however a lower relative densities of about 98 % t.d. was always achieved, regardless of the applied temperature profile. The best results were obtained with TZ-8Y using Spark plasma sintering and Rapid rate sintering. Smaller grain size was obtained as compared with conventional methods of other authors. The difference in grain size was just within the framework of the standart deviation. This work doesn’t show any positive influence of Rapid rate sintering on the resulting grain size