水晶、サファイア単結晶の室温における破壊じん性(<小特集>セラミック材料小特集)

概要

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The fracture toughness (K_<IC>) was measured for quartz and sapphire single crystals as a function of crystal orientation at room temperature. The controlled surface flaw method popularized by J. J. Petrovic et al. was employed in this experiment. Knoop indentor was used to introduce a semicircular microflaw on the surface of the specimen. Then the 3-point bending rupture strength was measured and K<IC> was calculated from the flaw size and strength. Five kinds of crystal orientations, namely (0001), (011^^-0), (011^^-1), (112^^-0) and (112^^-1) planes as fracture surface, were used for quartz, and four crystal orientations, namely (0001), (11^^-00) , (11^^-02) and (112^^-0) planes as fracture surface, were used for sapphire. The relation between K<IC> and the Young's elastic modulus (E) perpendicular to the fracture surface was investigated. It is expected from the theoretical consideration that K<IC> follows a linear dependence of E. The linear relation between K<IC> and E was actually observed for both quartz and sapphire single crystals. This kind of relation was also reported for MgAl_2O_4 single crystal. The K<IC> vs. E plot shows different lines for different crystals, namely quartz, sapphire and MgAl_2O_4. As a consequence, it is concluded that the proportional constant of this relation is dependent on the crystal structure.
社団法人日本材料学会の論文
1981-10-15