Novel ceramic substrates for high Tc superconductors

Abstract

A group of complex perovskite oxides REBa2NbO6 (RE = La and Dy) have been synthesized and developed for their use as substrates for both YBa2Cu3O7-δ and Bi(2223) superconductors. These materials have a complex cubic perovskite (A2BB′O6) structure with lattice constants, a = 8.48-8.60 angstrom. REBa2NbO6 did not show any phase transition in the temperature range 30-1300°C. The thermal expansion coefficient, thermal diffusivity and thermal conductivity values of REBa2NbO6 are favourable for their use as substrates for high Tc superconductors. The dielectric constant and loss factor of REBa2NbO6 are in a range suitable for their use as substrates for microwave applications. Both YBa2Cu3O7-δ and Bi(2223) superconductors did not show any detectable chemical reaction with REBa2NbO6 even under extreme processing conditions. Dip coated YBa2Cu3O7-δ thick films on polycrystalline REBa2NbO6 substrate gave a Tc(0) of 92 K and a current density of approx. 1.1 × 104 A/cm2 and Bi(2223) thick film on polycrystalline REBa2NbO6 substrate gave a Tc(0) of 110 K and a current density of approx. 4 × 103 A/cm2 at 77 K and zero magnetic field. A laser ablated YBa2Cu3O7-δ thin film deposited on polycrystalline REBa2NbO6 substrate gave a Tc(0) of 90 K and a current density of approx. 5 × 105 A/cm2.