Novel ceramic substrates for high T-c superconductors

A group of complex perovskite oxides REBa2NbO6 (RE =La and Dy) have been sy nthesized and developed for their use as substrates for both YBa2Cu3O7-delt a and Bi(2223) superconductors, These materials have a complex cubic perovs kite (A(2)BB'O-6) structure with lattice constants, a = 8.48-8.60 Angstrom. REBa2NbO6 did not show any phase transition in the temperature range 30-13 00 degrees C. The thermal expansion coefficient, thermal diffusivity and th ermal conductivity values of REIBa2NbO6 are favourable for their use as sub strates for high T-c superconductors, The dielectric constant and loss fact or of REBa2NbO6 are in a range suitable for their use as substrates for mic rowave applications. Both YBa2Cu3O7-delta and Bi(2223) superconductors did not show any detectable chemical reaction with REBa2NbO6 even under extreme processing conditions. Dip coated YBa2Cu3O7-delta thick films on polycryst alline REBa2NbO6 substrate gave a T-c(O) of 92 K and a current density of s imilar to 1.1 x 10(4) A/cm(2) and Bi(2223) thick film on polycrystalline RE Ba2NbO6 substrate gave a T-c(O) of 110 K and a current density of similar t o 4 x 10(3) A/cm(2) at 77 K and zero magnetic field. A laser ablated YBa2Cu 3O7-delta thin film deposited on polycrystalline REBa2NbO6 substrate gave a T-c(0) of 90 K and a current density of similar to 5 x 10(5) A/cm(2).