Abstract

The reliability of fundamental studies of superconductivity depends on the quality of the materials under study. Optical zone melting yields high-quality single crystals without impurities, which can be difficult for other technologies. The paper describes the growth procedure for single crystals of several families of superconductors: bismuth high-temperature superconductors Bi₂Sr₂CaCu₂O_{8 + δ} and Bi₂Sr_2–xLa_xCuO_{6 + δ} and a superconductor with an assumed p symmetry of the superconducting order parameter Sr₂RuO₄. We discuss the search criteria for synthesizing high-temperature yttrium superconductors YBa₂Cu₃O_{7 + δ} by optical zone melting, which do not lead to the formation of single crystals. The procedure for obtaining single crystals includes several stages. The first is to anneal a mixture of powders of the required oxides and carbonates, taken in specific proportions, at temperatures up to 850°C. A solid-phase reaction takes place, resulting in the desired polycrystalline complex oxide; rods with a length of ~5–10 cm are obtained from this oxide using a hydraulic press. The second stage is annealing of the rods in air at temperatures up to 940°C and, if necessary, melting in an optical-zone-melting unit using lamps with a rated power of 500 W at an adjustable power from 20 to 95% with a drawing speed of 20–30 mm/h. The third stage is the growth of a single crystal at 20–95% power at a rate of 0.1–20 mm/h. The result is a mixture that disintegrates upon cracking into single crystals up to several millimeters in size. Measurements of the temperature dependence of the dynamic magnetic susceptibility of the synthesized single crystals at a frequency of 100 kHz are carried out, which makes it possible to determine the temperature of the superconducting transition and its width.

中文翻译：

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使用光学区域熔融生长超导体单晶

摘要

超导基础研究的可靠性取决于所研究材料的质量。光学区熔化产生高质量的无杂质单晶，这是其他技术难以做到的。该论文描述了几个超导体家族的单晶的生长过程：铋高温超导体 Bi ₂ Sr ₂ CaCu ₂ O _{8 + δ}和 Bi ₂ Sr _{2– x} La _x CuO _{6 + δ}以及假设p超导有序参数Sr ₂ RuO _{4的对称性}. 我们讨论了合成高温钇超导体 YBa ₂ Cu ₃ O _{7 + δ的搜索标准}通过光学区熔化，这不会导致单晶的形成。获得单晶的过程包括几个阶段。第一种是在高达 850°C 的温度下以特定比例对所需氧化物和碳酸盐的粉末混合物进行退火。发生固相反应，产生所需的多晶复合氧化物；使用液压机从这种氧化物中获得长度约为 5-10 厘米的棒。第二阶段是在温度高达 940°C 的空气中对棒材进行退火，如有必要，使用额定功率为 500 W 的灯以 20 至 95% 的可调功率在光学区熔化单元中熔化拉丝速度为 20-30 毫米/小时。第三阶段是在 20-95% 功率下以 0.1-20 mm/h 的速率生长单晶。结果是一种混合物，它在裂化成尺寸达几毫米的单晶时分解。以 100 kHz 的频率测量合成单晶的动态磁化率的温度依赖性，这使得确定超导转变的温度及其宽度成为可能。