Motivated by the discovery of superconductivity in bilayer ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ at 80 K and the increased superconducting transition temperature, $T_{\text{c}}$, up to 96 K in single crystals of ${\mathrm{La}}_{1.57}{\mathrm{Sm}}_{1.43}{\mathrm{Ni}}_2{\mathrm{O}}_{7-\delta }$ under pressure, we systematically study the effect of Sm substitution on the superconductivity and structure of ${\mathrm{La}}_{3-x}{\mathrm{Sm}}_x{\mathrm{Ni}}_2{\mathrm{O}}_7$ ($0\le x\le 1.5$) under pressure. Experimental investigations in polycrystalline samples reveal that Sm substitution monotonically decreases the lattice constants $c$ and $a$, thereby enhancing crystal structural distortion and leading to an evolution of the metallic ground state in ${\mathrm{La}}_3{\mathrm{Ni}}_2{\mathrm{O}}_7$ to an insulating state in ${\mathrm{La}}_{1.5}{\mathrm{Sm}}_{1.5}{\mathrm{Ni}}_2{\mathrm{O}}_7$. The optimal $T_c^{\text{onset}}$ rises with increasing Sm substitution, and the maximum $T_c^{\text{onset}}$ is 89.2 K in polycrystalline ${\mathrm{La}}_{1.5}{\mathrm{Sm}}_{1.5}{\mathrm{Ni}}_2{\mathrm{O}}_7$. Divergences in $T_c$ compared with single crystals of ${\mathrm{La}}_{1.57}{\mathrm{Sm}}_{1.43}{\mathrm{Ni}}_2{\mathrm{O}}_{7-\delta }$ are likely due to variations in the microstructure induced by different material growth approaches. Our results suggest that the enhancement of $T_c$ in ${\mathrm{La}}_{3-x}{\mathrm{Sm}}_x{\mathrm{Ni}}_2{\mathrm{O}}_7$ is mainly affected by the compressed $c$ lattice before saturation, and the superconducting transition pressure increases with substitution concentration. Our experimental results provide insight into the influence of small-radius rare-earth element substitution on nickelate superconductors, offering a means to further increase the transition temperature.

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• Doping effects
• Electrical conductivity
• Growth
• Pressure effects
• Superconducting phase transition
• Superconductors