Effect of yttrium substitution on the superconducting properties of the   system La$_{1-\textit{x}}$Y$_{\textit{x}}$O$_{0.5}$F$_{0.5}$BiS$_{2}$
  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. 
I. Jeon, D. Yazici, B. D. White, A. J. Friedman, and M. B. Maple
cond-mat.supr-con cond-mat.str-el