Effect of Pressure on The Structural and Electrical Characteristics of Tl_(0.8)Sb_(0.2)Sr_2Ca_2Cu_3O_(9-δ) Superconductors Prepared by Solid state Reaction Technique

摘要

In this work three sets of superconducting samples with composition Tl_(0.8)Sb_(0.2)Sr_2Ca_2Cu_3O_(9-δ) prepared by the solid state reaction techniques. The appropriate amount of Tl_2O_3, Sb_2O_3, SrCO_3, CaCO_3 and CuO of 99.99% purity were used as starting raw material and were mixed. The mixed powder was initially calcinated at constant temperature of 800C~0 and the pallets of diameter 1.2 cm and thickness (0.2-0.3) cm were prepared under the pressures 7 Ton/cm~2 (sample A), 10 Ton /cm~2 (sample B) and 13Ton /cm~2 (sample C). Then the pallets were subjected to several cycles of sintering at constant temperature in the furnace and allowed to furnace cool to room temperature in oxygen rate 0.5 L/min. The resistivity measurements were carried out on these samples in the temperature range 77 K - 300 K. The standard four-probe technique was used to measure the resistivity of the samples. The samples A, B and C showed the onset superconducting transition temperatures (T_(conset)) at 121K, 124 K, and 128 K respectively. Samples A and B showed broad transitions while sample C showed a sharp drop indicating the presence of only one superconducting phase Tl-1223 in the sample. The XRD data collected from various samples were all polycrystalline. The transition temperature, oxygen content (δ) and the lattice parameter increase with increasing the pressure.