Determination of parameters of a system of charge carriers in Y1–2x Ca x Pr x Ba2Cu3O y within a combined analysis of temperature dependences of thermoelectric power and Nernst–Ettingshausen coefficients

Abstract

The temperature dependences of thermoelectric power S and transverse Nernst–Ettingshausen effect Q in high-temperature superconductors of the Y1–2xCaxPrxBa2Cu3Oy system with different concentrations of dopants have been investigated experimentally. It has been shown that all the specific features revealed in the behavior of the two kinetic coefficients under investigation can be described using the narrowband model with a single concept of the structure of an energy spectrum and a common set of model parameters that characterize the structure of the spectrum and properties of a system of charge carriers. Based on the quantitative analysis of the dependences S(T) and Q(T), the values of these parameters for samples of the studied composition have been determined and the character of their changes with an increase in the impurity content has been analyzed. It has been demonstrated that, for the explanation of the obtained results, it is necessary to take into account the interaction of calcium and praseodymium ions upon their simultaneous introduction into the lattice. It has been found that the mobility of charge carriers has extremely low values and almost does not depend on the level of doping, which is associated with the character of changes in the structure of the energy spectrum of Y1–2xCaxPrxBa2Cu3Oy upon doping. It has been concluded that the structure of the energy spectrum of high-temperature superconductors in the yttrium system is characterized by an asymmetry of the dispersion curve.