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$_{2}$

TL;DR

This study investigates how yttrium substitution affects the superconducting properties of La$_{1-x}$Y$_x$O$_{0.5}$F$_{0.5}$BiS$_{2}$, revealing that chemical pressure alters lattice parameters but does not induce high-$T_c$ phases.

Contribution

It provides new insights into the effects of yttrium substitution on lattice structure and superconductivity in La-based BiS$_2$ compounds, without inducing high-$T_c$ phases.

Findings

Y substitution reduces lattice parameter a and unit cell volume V.

A correlation exists between lattice c, La-O-La bond angle, and $T_c$.

Chemical pressure from Y substitution does not produce high-$T_c$ phase.

Abstract

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.