SINGLE-CRYSTAL GROWTH AND CHARACTERIZATION OF NARROW-GAP (TLBISE2)(1-X)-(TLBIS2) MIXED-CRYSTALS

Large single crystals of the family of layered compounds (TlBiSe2)(1-x )-(TlBiS2)(x) were grown by the Bridgman-Stockbarger method for x = 0. 0, 0.25, 0.50, 0.75 and 1.0. The structures of the as-grown single cry stals were determined by x-ray diffraction and the lattice parameters and unit cell volumes were obtained. Infrared reflectivity measurement s were also performed in the range 600-4000 cm(-1). From the analysis, the parameters epsilon(x), omega(rho) and Gamma were calculated. The electrical resistivities rho(parallel to) and rho(perpendicular to) (p arallel and perpendicular to the layers, respectively) were measured a s a function of temperature. From the rho(parallel to) measurements th e plot of the Debye temperature versus x was calculated. An attempt wa s also made to correlate these physical properties with the compositio nal parameter x.