Am. John et al., Barium rare-earth hafnates: Synthesis, characterization, and potential useas substrates for YBa2Cu3O7-delta superconductor, J AM CERAM, 82(6), 1999, pp. 1421-1424
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.