Generation and Mobility of Electronic Charge Carriers in Y1Ba2Cu3Ox

The Hall effect and the conductivity of Y₁Ba₂Cu₃O_x have been measured together for quenched specimens at room temperature as functions of oxygen content (x) in the range of 6 < × < 7. It has been reconfirmed that a hole is generated per every oxygen atom incorporated in the orthorhombic phase (x > 6.5) and per every two oxygen atoms in the tetragonal phase (x < 6.5). The exothermic enthalpy change for hole generation is 2 times or more larger in the tetragonal than in the orthorhombic phase. The mobility of the majority carrier holes has been found to vary discontinuously crossing the phase boundary (x ? 6.5), reflecting a first-order phase transition for these quenched specimens. It is independent of oxygen content in each structure: 0.34 ± 0.03 cm²/(V·s) in the tetragonal phase and 0.51 ± 0.06 cm²/(V·s) in the orthorhombic phase.