We present the effect of yttrium substitution on superconductivity in the La$_{ 1-\textit{ x}}$Y$_{ \textit{ x}}$O$_{ 0.5}$F$_{ 0.5}$BiS$_{ 2}$ system. Polycrystalline samples with nominal Y concentrations up to 40% were synthesized and characterized via electrical resistivity, magnetic susceptibility, and specific heat measurements. Y substitution reduces the lattice parameter \textit{ a} and unit cell volume \textit{ V}, and a correlation between the lattice parameter \textit{ c}, the La-O-La bond angle, and the superconducting critical temperature $T_c$ is observed. The chemical pressure induced by Y substitution for La produces neither the high-$T_c$ superconducting phase nor the structural phase transition seen in LaO$_{ 0.5}$F$_{ 0.5}$BiS$_{ 2}$ under externally applied pressure.
Categories: cond-mat.supr-con cond-mat.str-el