The high-pressure and high-temperature synthesis of HgBa<sub>2</sub>CaCu<sub>2</sub>O<sub>6+ delta </sub> and HgBa<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>8+ delta </sub> superconductors and their characterization
Y J Su; Y S Yao; G S Che; S L Jia; C Dong; G H Cao; Z X Zhao; Y J Su; Inst. of Phys., Acad. Sinica, Beijing, China; Y S Yao; Inst. of Phys., Acad. Sinica, Beijing, China; G S Che; Inst. of Phys., Acad. Sinica, Beijing, China; S L Jia; Inst. of Phys., Acad. Sinica, Beijing, China; C Dong; Inst. of Phys., Acad. Sinica, Beijing, China; G H Cao; Inst. of Phys., Acad. Sinica, Beijing, China; Z X Zhao; Inst. of Phys., Acad. Sinica, Beijing, China
Журнал:
Superconductor Science and Technology
Дата:
1995-01-01
Аннотация:
The superconductors HgBa<sub>2</sub>CaCu<sub>2</sub>O<sub>6+ delta </sub> (Hg-1212) and HgBa<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>8+ delta </sub> (Hg-1223) have been synthesized by solid state reaction, carried out at 850 degrees C under 25 kbar, using the nominal composition of HgBa<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>x</sub>. The results indicate that the optimum sintering time for the Hg-1223 phase is about 0.5 h. With increasing sintering time, the Hg-1223 phase decomposes, and the Hg-1212 phase increases gradually. When the sintering time increased to 3.8 h, we obtained a sample with nearly a single phase of Hg-1212. We synthesized the HgBa<sub>2</sub>CaCu<sub>2</sub>O<sub>6+ delta </sub> superconductor under 27 kbar at various sintering temperatures using the nominal composition of HgBa<sub>2</sub>CaCu<sub>2</sub>O<sub>x</sub>. The results indicate that the optimum sintering temperature for the Hg-1212 phase is 820-830 degrees C. The effect of annealing at various temperatures in flowing O<sub>2</sub> on the superconductivity of HgBa<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>8+ delta </sub> has been investigated.
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