Correlation of anomalies in temperature dependences of electrical resistance and thermal deformation of YBa2Cu3O7-δ ceramics

Direct measurements of the temperature dependences of the electrical resistance and the thermal deformation of the lattice parameters in microcrystalline YBa 2 Cu 3 O 7-δ (YBCO) with two dominant superconducting phases (DSPs) were carried out in the normal state and in the temperature range of superconducting transition (Δ T c ∼ 10 K). The presence of a linear correlation between the temperature coefficients of electrical resistance (TCR) and the thermal (volume) expansion (TEC) was shown – below (is direct) and above (is reverse) the temperature of the transition to the pseudogap state (∼ 160 K) with a correlation coefficient of no less than 0.98. As it established from the dependences of the derivatives of resistance on temperature for each of these phases the temperature dependences of the lattice parameters demonstrated discontinuity in the region of average values of the transition temperatures to the superconducting state ( T c ≈ 90.5 K and T c ≈ 87 K). Deviations from the zero TCR value for these phases at mid- Т с were positive and changes in TEC of all lattice parameters at these temperatures occurred to be with sign inversion. The scenario for the phenomena of charge excitations in YBCO and their pairing associated with anomalous compression of the volume of lattice upon cooling to T c and its subsequent positive striction directly in T c in the absence of a magnetic field is present. • YBCO ceramics with two dominant superconducting phases were studied. • The coefficients of resistance and expansion in the normal phase are correlated. • The coefficient of volumetric expansion changes sign during the transition. • During the transition, the volume first contracts and then suddenly grows.