酸化物超伝導体の破壊強度・靱性評価と破壊過程での超伝導性

抄録

Tensile strength of sintered YBCO superconductor at 77K was evaluated by Brazilian test and fracture toughness at 85K was measured by use of round compact tention specimen. Superconductivity of specimens during Brazilian tests were examined by the four-point terminal method. Density of a specimen was the principal factor of tensile strength and the fracture surface exhibited the cleavage-intergranular mixed pattern. No change in superconductivity of specimens was observed until mechanical fracture occurred. Namely, no stress dependence on superconductivity was observed for these material tested. Fracture toughness K_Q of sintered YBCO was also measured by use of a round compact specimen. The K_Q value of sintered YBCO with a density of 4, 84g/cm³ was 1.1Mpa·m^l/2. The obtained K_Q shows the value of one third or quarter compared with that of ordinary ceramics (ZrO₂, Al₂O₃).