Reseach On Preparation And Properties Of (α’+β’)-Sialon Multiphase Ceramics

(α’+β’)-Sialon ceramics was synthesized by pressureless sintering using α-Si3N4、β-Si3N4、Al2O3、AlN、CaO、Y2O3 powders. We discussed the effect of α’/β’ ratio, Ca2+/Y3+ ratio of a-Sialon phase and YA(42.95wt%Al2O3 +57.05wt%Y2O3) on (α’+β’)-Sialon ceramics. The results show that:(1) With the increasing of the ratio of the α’ and β’ phase from the design formulation and the content of Y3+, the bulk density of the (α’+β’)-Sialon composite ceramics, the bending strength and rockwell hardness (HRA) of the samples were increased, respectively.(2) In the sintering process of preparing multiphase ceramics, β’-Sialon phase was generated before a’-Sialon phase, then continued to reactive into a’-Sialon phase in the liquid phase. When the sintering temperature was 1800℃, the bulk density of the composite ceramics reached the maximum. When the sintering temperature increased to 1900℃, the density decreased and the column structure of P’-Sialon grain convert to flake-shape grain which had a irregular distribution. Through EDS analysis we can see that it contained Si, Al, O and N elements. With the increase of Y3+ content in the a’-Sialon phase, the convertion process was accelerated.(3)The calculation and analysis of crystal cell parameters show that:when the sintering temperature rised to 1700℃, the interstitial cation Ca2+ and Y3+ began to inter the cell of a’-Sialon phase gradually and the crystal cell parameters a, c enlarged. As temperature rised up to 1900℃, Ca2+ and Y3+ was still stably in a’-Sialon unit cell.(4)Adding the YA could promote the densification of Sialon multiphase ceramics and delay the decomposition of sialon multiphase ceramics in a certain extent. When adding 9wt% YA, the density, rockwell hardness(HRA) and bending strength of sialon multiphase ceramics were up to 3.24g/cm3,90.1 (HRA) and 450.24MPa, respectively.(5)The peak (210) of P’-Sialon phase moved to the right in the sialon multiphase ceramics with 9wt% YA. It indicated that in the process of lowing the temperature the residual glass phase had residual stress on β’-Sialon grain.