Upadhyayula V Varadaraju

The effect of oxide additives-CuO, SiO2, Y2O3, Bi2O3 and ZnO in 1-10 mol% on the sintering and superconducting properties of YBa2Cu3O7 was studied. SEM studies indicated improvement of grain size and interconnectivity due to the additives, the best results being obtained with Bi2O3, SiO2 and Y2O3. The superconducting transition temperature is unaffected (92±2 K) even with 10 mol % of the additives. ZnO, however, decreases the T c as expected. © 1989 Indian Academy of Sciences.

Thick films of the high T csuperconducting oxides, LnBa2Cu3O7, Ln = Eu, Y, have been fabricated by screen printing on alumina and SrTiO3 substrates. Conditions for optimum superconductivity behaviour of the films have been established. T c onset varies from 90-94 K for all the films but zero resistance was observed only in a few cases. © 1988 Indian Academy of Sciences.

The absolute thermopower of single phase YBa2Cu3O7 and Y0.8Er0.2Ba2Cu3O7 has been measured in the range 250 K to the superconducting transition temperature. It is found that these compounds show a large enhancement of thermopower in the range 150 K down to T c. This enhancement shows a steep exponential drop as the temperature increases from the transition temperature. The temperature variation of the enhancement is too steep to be accounted for by electron-phonon or electron-local structural excitation mechanisms. © 1987 Indian Academy of Sciences.