Fabrication and characterization of Bi1.6Pb0.4Sr2Ca2Cu3Oy superconductors prepared by solid state reaction technique

Abstract

In this work three sets of superconducting samples with composition Bi 1.6 Pb 0.4 Sr 2 Ca 2 Cu 3 O y were prepared by the solid state techniques and resistivity measurements were carried out on these samples in the temperature range 77 K – 175 K. The standard four-probe technique was used to measure the resistivity of the samples. The appropriate amount of Bi 2 O 3 , PbO, 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 820 0 C and the pallets of diameter 14 mm and thickness 1-2mm were prepared under the pressures 200 kg/cm 2 (sample A), 300 kg/cm 2 (sample B) and 250 kg/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 air. The resistivity measurements were carried out on these samples using locally made resistivity probe. Rh-Fe resistance thermometer was used to measure the temperatures of the sample. The samples A, B and C showed the onset superconducting transition temperatures at 103 K, 111 K, and 110 K respectively. Samples A and B showed broad transitions while sample C showed a sharp drop indicating the presence of only one superconducting phase Bi 2223 in the sample.