| 摘要 |
PURPOSE:To obtain the high-toughness monolithic Si3N4 sintered body with its fracture toughness specified by forming the sintered body with a B-Si3N4 columnar crystal in which the average minor axis of a specified number of large diameter columnar crystals appearing in a specified cut-out area is specified. CONSTITUTION:The Si3N4 sintered body consists of a B-Si3N4 in which the average minor axis of the five large diameter crystals appearing in the cut-out area of 7000mum<2> is controlled to 6-20mum. The fracture toughness of the sintered body is adjusted to >=8MPa.m<1/2>. The conventional material used in the production of a ceramic sintered body is used as the material for the Si3N4 powder to be used in the production of the Si3N4 sintered body. The material having a high alpha conversion ratio is preferably used, and the content of the alpha type is adjusted to >=90% or preferably to >=95%. The sintering condition is set so that the minor axis of the columnar crystal and the fracture toughness of the sintered body are confined within specified limits. The sintering temp. is especially effective as the set condition and controlled to >=1900 deg.C or to 1900-2000 deg.C, for example. |
