Single Crystal Elastic Constants of b-Silicon Nitride Determined by X-Ray Powder Diffraction
Keisuke TANAKA, Kenji SUZUKI, Yoshihisa SAKAIDA, Hirohisa KIMACHI and Yoshiaki AKINIWA
Abstract:The X-ray elastic constants of pressureless sintered b-silicon nitride (Si3N4), were experimentally determined for ten different diffractions by using Ka radiations of Cu, Co, Fe, Cr and V. The X-ray compliances, (1+v'‚˜)/E'‚˜ and v'‚˜/E'‚˜ (E'‚˜= Young's modulus, v'‚˜=Poisson's ratio), change as a second power function of cos2f (f=angle between the diffraction plane normal and the c-axis of hexagonal crystal). Using the simplex method, the elastic constants of single crystals of b-silicon nitride were determined from the measured values of the X-ray compliances on the basis of the average of Voigt and Reuss models and Kroener's model, combined with the self-consistent analysis of multi-phase materials. The obtained result SHOWS a high stiffness in the c-direction of hexagonal crystals, but the degree of anisotropy is not so large as the whisker data reported by Hay et al. Key Words:Stress measurement, X-ray method, Elastic constant, b-silicon nitride, Simplex method