Abstract
Solid solutions of the formula La 2−xLn xCuO 4 (Ln = Pr, Nd) possess the orthorhombic structure of La 2CuO 4 for small values of x and transform to the tetragonal Nd 2CuO 4 structure at a critical value of x. At the critical composition, there is an abrupt change in specific volume as well as the c a ratio. The material exhibits temperature-independent electrical resistivity below the critical value x and semiconducting behaviour above it. The specific volume and c a ratio smoothly decrease with increase in x in the La 2Cu 1−xNi xO 4 system, although the solid solution possess the tetragonal K 2NiF 4 structure when x>0.1. Compositions with x>0.1 exhibit a gradual semiconductor metal transition similar to that of La 2NiO 4, the transition temperature decreasing with increasing x.
Published Version
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