Structural transitions in (La,Ln)2CuO4 and La2(Cu,Ni)O4 systems

Singh, K. K. ; Ganguly, P. ; Rao, C. N. R. (1982) Structural transitions in (La,Ln)2CuO4 and La2(Cu,Ni)O4 systems Materials Research Bulletin, 17 (4). pp. 493-500. ISSN 0025-5408

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Solid solutions of the formula La2−xLnxCuO4 (Ln=Pr, Nd) possess the orthorhombic structure of La2CuO4 for small values of x and transform to the tetragonal Nd2CuO4 structure at a critical value of x. At the critical composition, there is an abrupt change in specific volume as well as the c̲/a̲ ratio. The material exhibits temperature-independent electrical resistivity below the critical value x and semiconducting behaviour above it. The specific volume and c̲/a̲ ratio smoothly decrease with increase in x in the La2Cu1−xNixO4 system, although the solid solution possess the tetragonal K2NiF4 structure when x>0.1. Compositions with x>0.1 exhibit a gradual semiconductor metal transition similar to that of La2NiO4, the transition temperature decreasing with increasing x.

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Deposited On:02 Jun 2011 13:14
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