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Theory on the Structure of Twin Boundaries in La2−x,BaxCuO4

Published online by Cambridge University Press:  15 February 2011

Zhi-Xiong Cai
Affiliation:
Materials Science Division, Brookhaven National Laboratory, Upton NY 11973, USA
David O. Welch
Affiliation:
Materials Science Division, Brookhaven National Laboratory, Upton NY 11973, USA
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Abstract

The structure of the twin boundary in the low-temperature-orthorhombic phase of La2−xBaxCuO4 is studied using a Landau-type free energy model which reproduces the xT phase diagram. The La2−xBaxCuO4 compound has a body-centered tetragonal (HTT) structure at high temperatures. Upon cooling it undergoes a structural phase transition to a low-temperature orthorhombic structure (LTO structure) which is caused by the tilting of the CuO6 octahedra about the (110) and (110) directions. Depending on the doping level x, the LTO structure may go through another phase transition at an even lower temperature to a low-temperature tetragonal phase (LTT phase). We find that the existence of LTT phase greatly changes the characteristics of the twin boundary in the LTO phase. LTT phase exists at twin boundaries of the LTO phase at temperatures well above the LTT to LTO transition temperature.

Type
Research Article
Copyright
Copyright © Materials Research Society 1995

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