Japanese Journal of Applied Physics · 1988 · 12 citations · 11 references
Natural SciencesMaterials SciencePhysicsCondensed Matter PhysicsMaterials PhysicsSolid State PhysicsCarrier TransportDopingStrongly Correlated Electron SystemsSuperconducting MaterialsCarrier ConcentrationCarrier Concentration ControlCarrier Concentration OptimizationCuprate SuperconductorsHigh-temperature SuperconductivityHigh-temperature SuperconductorsSuperconducting Critical TemperatureTemperature Dependence Of Electrical Properties
Systems of solid solution Ln 1- x Ca x Ba 2 Cu 3 O 7-δ (Ln=Nd, La, Pr) have been investigated in order to clarify the effect of hole-doping on the superconducting state. The transition temperature T c decreases with increasing Ca-ion substitution in either Nd 1- x Ca x Ba 2 Cu 3 O 7-δ or La 1- x Ca x Ba 2 Cu 3 O 7-δ . Combined with the fact that the electron-doping in the system Ln 1+ x Ba 2- x Cu 3 O 7-δ (Ln=La, Nd, Eu) decreases T c , the experiment indicates that the nondoped LnBa 2 Cu 3 O 7-δ (Ln=Nd, La) has an optimum carrier concentration for T c . For the nonsuper-conducting Pr 1- x Ca x Ba 2 Cu 3 O 7-δ , the conductivity at 77 or 280 K exhibits a maximum at the formal valence of ca. 3 for Pr 1- x Ca x .
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Oxygen ordering and superconductivity in La(Ba2−xLax)Cu3O7+δ
Carlo U. Segre, B. Da̧browski, D. G. Hinks et al. · Nature · 1987 · 166 citations