Ferroelectric polarization of Pb_0.92La_0.08(Zr_0.52Ti_0.48)O< sub>3 modulating the electrical properties of YBa₂Cu₃O_{7_8}

Pb0.92La0.08(Zr0.52Ti0.48)O3/YBa2Cu3O7_ 8 (PLZT/YBCO) heterostructure was prepared via the photosensitive sol-gel method (P-SG) combined with pulsed laser deposition (PLD). Test results show that the preparation process of PLZT film does not significantly cause degradation of the superconductivity of underlying YBCO film, and the PLZT has good ferroelectric properties in the temperature range of 300-50 K. With decreasing temperature, ferroelectric domain formation and inversion become more difficult, which causes coercive field (Ec) of PLZT to increase. However, remanent polarization (Pr) remains almost constant with decreasing temperature. Furthermore, it is found that the critical transition temperature (Tc) of YBCO decreases and resistance of nonsuperconducting state of YBCO increases as positive electric field applied to PLZT increases, while Tc and the resistance of non-superconducting state of YBCO do not change when negative electric fields are applied. It is believed that polarization charges regulate Fermi level of PLZT, which results in the promotion (hindrance) of electron injection into YBCO for positive (negative) applied electric fields, thereby regulating Tc and the resistance of non-superconducting state of YBCO. When positive applied electric fields are removed, the superconducting properties of YBCO in PLZT/YBCO structure cannot be restored to their initial values due to the remanent polarization of PLZT.