Method for producing biaxially aligned super conducting ceramics

A method for producing highly textured, biaxially aligned superconducting ceramics in composite conductor forms comprising the steps of:

• forming a metallic precursor for a YBCO 123 superconducting compound and introducing the precursor into a plurality of sheaths, each sheath comprising a noble metal or its alloy,
• deforming a bundle comprising the sheaths in one or more iterations to form a precursor composite comprising fine, substantially planar precursor filaments surrounded by a malleable matrix having interfacial layers,
• thermomechanically processing the composite precursor in one or more steps at conditions selected to texture at least the interfacial layers of the matrix without converting appreciable amounts of the composite precursor to the desired superconducting oxide to form a preliminary filament material having no appreciable amounts of the desired superconducting oxide, and then
• reaction texturing the Preliminary filament material to form and texture the desired superconducting ceramic within the composite via growth fostered by the textured interfacial layers and substantially without deformation of the superconducting grains, where the reaction texturing step is a heat treatment in the 830 C. to 880 C. range with an initial portion of the reaction in a low oxygen potential gas at oxygen pressures in the range PO2<=exp[−32,000/T+23], where T is absolute temperature (K) and PO2 is oxygen pressure having a value in a range of from 0.009 to 0.002 atmospheres, followed by a second portion of the reaction in a higher oxygen pressure environment at oxygen pressures in the range 0.01<PO2<100 atmospheres.

A method for producing highly textured, biaxially aligned superconducting YBCO 123 in composite conductor forms comprising the steps of:

• forming a metallic precursor for the 123 phase of yttrium-barium-copper-oxide;
• introducing the precursor into a plurality of sheaths to form a plurality of filled sheaths, wherein interfacial layers are in intimate contact with the precursor and consist substantially of silver or a silver alloy;
• deforming a bundle comprising the filled sheaths in one or more iterations including to form a multifilamentary precursor composite comprising fine, substantially planar malleable precursor filaments;
• bi-axially texturing the interfacial layers via one or more deformation steps in the 170-600° C. temperature range;
• then, oxidizing the composite in the 250°-350° C. temperature range under conditions selected to preserve or enhance the texture in the interfacial layers and sufficient to form sub-oxide phases in the filaments but insufficient to convert appreciable amounts of the sub-oxide phases into a desired superconducting oxide;
• and, before, during or after oxidation,
• heat treating the composite so as to complete the development of bi-axial texture in the interfacial layers via an anneal in the 200°-900° C. temperature range in a low oxygen pressure environment that inhibits superconducting oxide phase formation at oxygen pressures within the limit set by the equation PO2<=exp [−32,000/T+23], where T is absolute temperature (K) and PO2 is oxygen pressure having a value in a range of from 4×10−20 to 0.01 atmospheres, wherein the oxidizing and heat treating steps form a preliminary filament material;
• then, reaction texturing the preliminary filament material at oxygen pressures exceeding the lower limit set by the equation PO2>=exp [−32,000/T+23], where T is absolute temperature (K) and PO2 is oxygen pressure having a value in the range 0.01<PO2<100 atmospheres, to form and texture the superconducting YBCO 123 phase within the composite via growth fostered by the textured interfacial layers and substantially without deformation of the superconducting grains;
• and,
• then annealing the composite in 0.1-10 atm oxygen in the 400°-600° C. temperature range to adjust the defect chemistry of the YBCO 123 for optimal performance.