An ultrasonic spray pyrolysis (USP) system has been used to deposit thick films of YBa_2Cu_3O_7-x on (100) LaAlO_3, YBCO buffered (100) MgO, and (110) Ag single crystal substrates. Nitrate precursors with a Y:Ba:Cu ratio of 1:2:0.6 have been used with a deposition temperature of 900 deg C. Growth rates of 0.25 mum per minute have resulted in epitaxial growth of biaxially aligned 5 mum thick YBa_2Cu_3O_7-x films. Lowering the nitrate precursor concentration and hence the growth rate has resutled in improved superconducting properties. Critical currents approaching 10~4 Acm~-2 have been achieved at 77K, and approx 10~5 Acm~-2 at 20K.
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