Cracking of rare earth barium cuprate films prepared by liquid phase epitaxy

A high growth rate of REBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (RE=rare earth elements) superconducting films is achieved with liquid phase epitaxy. The occurrence of cracks is one of the major problems for applications of these thick films. To achieve crack free films, it is necessary to understand the formation of cracks in REBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// films. Investigations were carried out on YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// and (Y,Pr)Ba/sub 2/Cu/sub 3/O/sub 7-/spl delta// films on NdGaO/sub 3/ substrates and on new SrPrGaO/sub 4/ substrates with tetragonal K/sub 2/NiF/sub 4/ structure (space group I4/mmm). A thermodynamic model for understanding the crack spacing together with mechanical properties determined in melt textured YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// bulk samples was applied.