Growth of Highly Oriented TlBa₂Ca₂Cu₃O_9—y Superconducting Films on Ag Substrates Using a Dip‐Coated Barium Calcium Copper Oxide Sol—Gel Precursor

Thin films of Ba_zCa₂Cu₃O₇ a precursor of TIBa₂, Ca₂‐Cu₃O_9‐y, were prepared by sol‐gel synthesis from an all alkoxide solution. The barium and calcium precursors were the respective metals reacted with 2‐methoxyethanol, and the copper precursor was copper methoxide complexed by triethanolamine. Silver substrates were coated using the sol‐gel solution by dip‐coating. Subsequent processing included a low‐temperature drying step (600°C), repeated coating to provide the desired thickness, heat treatment at 850°C in oxygen to remove carbon, and reaction at 860°C in a two‐zone thallination furnace to produce a TIBa₂Ca₂‐Cu₃O_9‐y, superconducting film. These films were strongly c‐axis‐aligned, had a zero‐resistance temperature (T₂) of 110 K, and a critical‐current density (J_c) of 1.9 × 10₄ A/cmZ at 77 K and zero magnetic field.