Synthesis and Properties of SmO<sub>0.5</sub>F<sub>0.5</sub>BiS<sub>2</sub> and Enhancement in <i>T</i><sub>c</sub> in La<sub>1–<i>y</i></sub>Sm<sub><i>y</i></sub>O<sub>0.5</sub>F<sub>0.5</sub>BiS<sub>2</sub>
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The crystal structure and properties of a new member of the oxybismuth sulfide family SmO0.5F0.5BiS2 are reported here. The compounds SmO1–xFxBiS2 (x = 0.0 and 0.5) are isostructural with LaOBiS2 and crystallize in the CeOBiS2-type structure (P4/nmm). Sm substitution in LaO0.5F0.5BiS2 (La1–ySmyO0.5F0.5BiS2) leads to a gradual decrease in the a-lattice constant; however, the c-lattice constant does not show such a gradual trend. Enhancement in Tc is achieved upon partial substitution of La by the smaller Sm ion. A maximum Tc ∼ 4.6 K was observed for composition with y = 0.8. Disobeying this trend, Tc disappears unexpectedly in the composition SmO0.5F0.5BiS2 (y = 1.0). Both the undoped and F-doped (x = 0.0 and 0.5) compounds are paramagnetic, exhibiting semiconducting behavior down to 2 K.
