Single crystal growth and properties of NdGaO₃, Nd_yPr_1−yGaO₃ and LaAl_1−xGa_xO₃ as substrates for high temperature superconductors

Preparation and properties of perovskite‐related single crystals of NdGaO₃, Nd_yPr_1−yGaO₃ and LaAl_1−xGa_xO₃ as substrates for superconducting films of Yba₂Cu₃O_7−δ and Pb₂Sr₂(Y,Ca)Cu₃O_8+δ have been studied. LaAl_1−xGa_xO₃ single crystals up to 4.5×4×2mm³ have been grown from PbO‐MoO₃–B₂O₃ flux. Powder x‐ray diffraction was used to determine x values which were 0.16, 0.19, and 0.80 and the lattice mismatch between substrate and film is about half that for LaAlO₃ and LaGaO₃. NdGaO₃ and Nd_yPr_1−yGaO₃ single crystals have been grown from a similar flux in the temperature range 1260–1080 °C so as to avoid the cubic to orthorhombic phase transition at 1350°. Twin‐free crystals up to 4×4×2 mm³ have been obtained. The lattice constants of gallates suitable for depositing films of both YBa₂Cu₃O_7−δ and Pb₂Sr₂(Y/Ca)Cu₃O_8+δ on (001) and (110) planes are investigated.