Barium rare-earth hafnates: Synthesis, characterization, and potential useas substrates for YBa2Cu3O7-delta superconductor

A new group of complex perovskites Ba2REHfO5.5 (where RE = La, Pr, Nd, and Eu) has been synthesized and sintered as single-phase materials with high s intered density and stability using a solid-state reaction method for the f irst time. The structure of Ba2REHfO5.5 has been studied by X-ray diffactom etry (XRD) and all of the perovskites are isostructural and have a cubic st ructure. The dielectric constant and loss factor values of these materials are in a range suitable for their use as substrates for YBa2Cu3O7-delta sup erconductors. XRD and resistivity measurements show that there is no detect able reaction between YBa2Cu3O7-delta and Ba2REHfO5.5, even when the two su bstances are mixed thoroughly and sintered at 950 degrees C for 15 h. The a ddition of Ba2REHfO5.5 up to 20 vol% in YBa2Cu3O7-delta-Ba2REHfO5.5 composi te shows no detrimental effect on the superconducting transition temperatur e of YBa2Cu3O7-delta Thick films of YBa2Cu3O7-delta fabricated on polycryst alline Ba2REHfO5.5 substrate have a superconducting zero resistivity transi tion of 92 K, indicating the suitability of these new materials as substrat es for YBa2Cu3O7-delta films.