Growth of Large (La_1-xSr_x)2CuO₄ Single Crystals and Reduction of Oxygen Deficit

Abstract

(La_1-xSr_x)₂CuO₄ quasiternary compounds possess a number of unique physical properties related to structural, magnetic, metal-dielectric and superconducting phase transitions. The problem of single crystal growth of these cuprates is very important for their comprehensive study. Its solution is complicated by incongruent melting and by the fact that all the materials of the technological equipment are heavily corroded by the fluxes. Lanthanum-strontium cuprates are grown from the lithium borate or sodium borate fluxes or stoichiometric copper oxide^1–3. The disadvantage of the borate solvents is the incorportion of impurity ions into the growing crystals, for instance, up to 8 at. % Li¹. The use of superstoichiometric CuO as a solvent excludes the incorporation of the impurities into the single crystals, although the decompositon of cupric oxide at elevated temperatures hampers the formation of single crystals with stoichiometric oxygen. The best results have recently been reported on the technique of slow pulling of seeds from the surface of the superstoichiometric flux-melt².