We have investigated the substitution effect of Eu on the superconductivity in La_2-xEu_xO₂Bi₃Ag_0.6Sn_0.4S₆. Recently, we reported an observation of superconductivity at 0.5 K in a layered oxychalcogenide La₂O₂Bi₃AgS₆. The Sn doping at the Ag site was found to raise the superconducting transition temperature, T_c, to 2.5 K in La₂O₂Bi₃Ag_0.6Sn_0.4S₆. To further improve the superconducting properties, we have partially substituted Eu for the La site to increase the chemical pressure in La_2-xEu_xO₂Bi₃Ag_0.6Sn_0.4S₆ (x = 0.1–0.6). La_2-xEu_xO₂Bi₃Ag0_.6Sn_0.4S₆ is crystallized in a tetragonal phase with the space group P4/nmm. With the increase in Eu concentration, x, the lattice constant a decreased, while the lattice constant c was marginally shortened, which suggests that the chemical pressure induced by the Eu doping is uniaxial along the a-axis. T_c increased with increasing x up to x = 0.4, and the suppression of superconductivity was observed for higher Eu concentrations of x = 0.5 and 0.6. From the magnetic susceptibility and resistivity measurements, a superconducting transition has been confirmed for x = 0.1–0.6 with T_c = 2.5–4.0 K, respectively. The estimated upper critical field (B_c2) was 3.5 T for x = 0.4, which also has the highest T_c. We observed the jump in the temperature dependence of heat capacity near T_c = 4.0 K for La_1.6Eu_0.4O₂Bi₃Ag_0.6Sn_0.4S₆, which confirms the emergence of bulk superconductivity in La_1.6Eu_0.4O₂Bi₃Ag_0.6Sn_0.4S₆.

我们研究了Eu对La _{2- x} Eu _x O ₂ Bi ₃ Ag _0.6 Sn _0.4 S _6中超导性的取代作用。最近，我们报道了在层状氧硫属化物La ₂ O ₂ Bi ₃ AgS _6中在0.5 K处的超导现象。发现在Ag位置处的Sn掺杂将La ₂ O ₂ Bi ₃ Ag _0.6 Sn _0.4 S _6中的超导转变温度T _c升高到2.5K。。为了进一步改善超导性能，我们用La代替了Eu，以提高La _{2- x} Eu _x O ₂ Bi ₃ Ag _0.6 Sn _0.4 S ₆（x  = 0.1-0.6）中的化学压力。La _{2- x} Eu _x O ₂ Bi ₃ Ag 0 _.6 Sn _0.4 S ₆以空间相为P 4 / nmm的四方晶态结晶。随着Eu浓度x的增加，晶格常数a降低，而晶格常数c略有缩短，这表明Eu掺杂引起的化学压力沿a轴是单轴的。T _c随着x的增加而增加，直至x  = 0.4，并且对于较高的Eu浓度x  = 0.5和0.6 ，观察到超导性受到抑制。通过磁化率和电阻率测量，分别在x  = 0.1-0.6和T _c  = 2.5-4.0 K的情况下证实了超导转变。x的估计上限临界场（B _c2）为3.5 T = 0.4，这也具有最高的T _c。我们观察到 La _1.6 Eu _0.4 O ₂ Bi ₃ Ag _0.6 Sn _0.4 S ₆在T _c = 4.0 K附近对热容的温度依赖性跃变，这证实了La _1.6 Eu _0.4 O ₂ Bi ₃ Ag的本体超导性的出现。_0.6锡_0.4 S ₆。