SILICON NITRIDE CERAMICS AND METHOD OF SINTERING AND FORMING THE SAME

PROBLEM TO BE SOLVED: To provide silicon nitride ceramics and a method of sintering and forming the same. SOLUTION: The method of sintering and forming the silicon nitride ceramics which is a method of manufacturing the silicon nitride ceramics having an orientation structure and excellent high-temperature strength of >=600 MPa bending strength 1,300 deg.C and comprises forming silicon nitride raw material powder consisting of at least >=1 kinds selected form α silicon nitride powder, and the powder, seed crystals and whiskers of β silicon nitride and a sintering additive containing >=1 kinds selected from ytterbium and rutetium to fabricate a preform, subjecting the preform to sintering and forming accompanied by plastic flow in the state of restraining portion of the preform to induce the plastic flow in at least a portion of the preform and controlling the orientation direction of the crystal grains in the respective segments of the sintered green body in the prescribed direction and the silicon nitride ceramics fabricated by this method.