Structural Study of the Solid Solutions in a CaSi 2-LaSi 2 System

Abstract

The crystal structure of the solid solutions in a CaSi 2-LaSi 2 system was studied by the X-ray Rietveld analysis. The layered structure of CaSi 2 was changed into the three-dimensional α-ThSi 2-type structure in the solid solutions Ca 1- x La x Si 2 (0.2 ≤ x ≤ 1.0). The lattice parameters of the solid solutions did not obey Vegard's rule. The structural analysis revealed that the Si-Si distances and the Si/ Si\\ Si bond angle of the three-coordinated coplanar group of the Si sublattice changed rather irregularly with the composition of the solid solutions. The Raman band due to the Si-Si stretching vibration was hardly influenced by the composition of the solid solutions. Magnetic susceptibility measurements suggested that the superconducting transition of the solid solution occurred at a temperature between 1.5 and 2.5 K.