SINTERING KINETIC STUDY OF 2Y-TZP/AL2O3 COMPOSITE DURING INITIAL STAGE OF SINTERING

Initial stage of sintering of nano crystalline 2 mol% yttria doped tetragonal zirconia polycrystal (2Y-TZP) with 2wt% alumina (2Y-TZP/Al2O3) was analyzed using different nonisothermal and pseudo-isothermal sintering techniques. Sintering behaviour of the composite material during constant rate of heating (CRH) was found to be dependent on calcination temperature. Kinetics of sintering was studied using pseudo-isothermal sintering method, i.e. stepwise isothermal densification (SID) technique. Although this method was expected to produce both 'n' and 'Q' simultaneously from a single experiment, the result obtained in the present experiment was not reliable, especially the 'Q' value obtained was abnormally large as compared to the value expected for a nano crystalline material. However, the same SID experiment was found to be useful to measure the activation energy by Dorn method. In the present investigation, activation energy of sintering was evaluated at different temperature regions using Dorn method. The modified Johnson equation was used for the direct determination of 'n' value. Incorporation of initial shrinkage correction during SID experiment yielded reliable 'Q' as well as 'n' values. Most interesting finding of the present study was that the sintering mechanism, as a function of calcinations temperature, was found to change from grain boundary to volume diffusion mechanism.