• K Ramakrishna

      Articles written in Bulletin of Materials Science

    • Electron microscopic observations of Bi and Tl bearing cuprate high temperature superconductors

      B Das K Ramakrishna G D Verma R S Tiwari O N Srivastava

      More Details Abstract Fulltext PDF

      The second generation of high temperature superconductors typified by Bi2Sr2Can−1CunO2n+4 and Tl2Ba2Can−1CunO2n+4 exhibits curious structural properties which have direct relevance to the superconducting behaviour particularly transition temperature (Tc). The present paper reports on investigations of structural properties at microlevel in Bi-bearing HTCS. We have found curious structural characteristics which manifests itself in the form of transformation fromap×ap×c to (2)1/2ap×(2)1/2ap×c through the loss of calcium atoms and the formation of five-fold modulated phase alongb through the loss of Ca and Sr atoms. We have also found the evidence of high periodicities (n=4) Bi2Sr2Ca3Cu4O12. The microstructural characteristics of HTCS showing the higherTc(R=0) ∼ 120 K exhibits unusual characteristics.

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