GENERATION AND MOBILITY OF ELECTRONIC CHARGE-CARRIERS IN Y1BA2CU3OX

The Hall effect and the conductivity of Y1Ba2Cu3Ox have been measured together for quenched specimens at room temperature as functions of ox ygen content (x) in the range of 6 < x < 7. It has been reconfirmed th at a hole is generated per every oxygen atom incorporated in the ortho rhombic phase (x > 6.5) and per every two oxygen atoms in the tetragon al 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 va ry discontinuously crossing the phase boundary (x similar or equal to 6.5), reflecting a first-order phase transition for these quenched spe cimens. It is independent of oxygen content in each structure: 0.34 +/ - 0.03 cm(2)/(V(.)s) in the tetragonal phase and 0.51 +/- 0.06 cm(2)/( V(.)s) in the orthorhombic phase.