Patent ID: 8579513

Claim:
A sliding member comprising a silicon nitride sintered compact containing, as sintering aids, a rare earth element of 7 to 18 mass % in twins of oxide, aluminum of 0.3 to 4 mass % in terms of oxide, and at least one element M selected from Ti, Zr, Hf, Mg, V, Nb, Ta, Cr, Mo and W of 0.1 to 3 mass % in terms of oxide, and having a total content of Li, Na, K, Ca, Sr, Ba, Fe, Mn and B as impurity positive ion elements of 0.3 mass % or less, wherein the silicon nitride sintered compact comprises silicon nitride crystal grains and grain boundary phases comprise mainly the sintering aids, the grain boundary phases comprise crystalline compound phases generated by crystallizing a part of the grain boundary phases, and a ratio of the crystalline compound phases in the grain boundary phases is 20% or more in area ratio, wherein an average grain size of the crystalline compound phases which exist in the grain boundary phases is 0.5 μm or less, and a maximum grain size of the crystalline compound phases which exist in the grain boundary phases is 1 μm or less, wherein the silicon nitride crystal grains comprise columnar grains having an aspect ratio of 2 or greater, a ratio of the columnar grains in the silicon nitride crystal grains is 50% or more in area ratio, and a maximum length of the columnar grains is 40 μm or less, and wherein a porosity of the silicon nitride sintered compact is 0.1% or less, and a thermal conductivity of the silicon nitride sintered compact is 60 W/m·K or higher.