Thick (∼ 20 μm) superconducting films of Y1 Ba2 Cu3 O7−x have been produced on 3 in. wafers of silicon, SiO2 ‐coated silicon, and sapphire. The process involves spraying of a slurry of finely ground powder of Y1 Ba2 Cu3 O7−x and methyl alcohol, followed by rapid thermal anneal for sintering. The Tc for Si, SiO2 , and sapphire are 70, 81, and 62 K, respectively. Post‐sinter anneal in oxygen at 400 °C further increases Tc . The adhesion of the films sintered above 980 °C is excellent.