Order-disorder in T, T′, and T* phase: Superconductors and related materials

J.M. GONZALEZ CALBET; M.J. SAYAGUEZ; A. VARELA; J.M. ALONSO; A. CANEIRO; M. VALLET-REGI

MICROSCOPY RESEARCH AND TECHNIQUE.

WILEY-LISS, DIV JOHN WILEY & SONS INC

Lugar: New York; Año: 1995 vol. 30 p. 193 - 207

1059-910X

After reviewing microstructural studies on superconducting materials showing T, T′,and T* structural types, results are presented on the microstructure of some n-typesuperconductors and related materials prepared with accurate control of the oxygenstoichiometry. Electron microscopy is used to describe the ordering of interstitialoxygen defects in T-type La2NiO4+δ leading to the formation of the n = 2 term of ahomologous series with the general formula La8nNi4nO16n+1. Structural transitions andsuperstructure formation in the Pr2−x−yCexSryCuO4-δ system are reported, where T, T′;,and T* phases are isolated as a function of both Ce and Sr content.