The new lanthanum chalcoantimonate TlLa₂Sb₃Se₉ has been synthesized and its crystal structure determined. TlLa₂Sb₃Se₉ crystallizes in an ordered variant of the KLa₂Sb₃S₉ type, space group P2₁2₁2₁ with the lattice parameters a=4.2621(2) Å, b=15.155(5) Å, c=25.505(9) Å. The band gap of TlLa₂Sb₃Se₉ was calculated to be 0.47 eV, and experimentally determined to be 0.68 eV. Its thermoelectric properties were optimized via doping with Ca²⁺; samples with the compositions TlLa_2‐xCa_xSb₃Se₉ (x=0.01, 0.03, 0.05) were synthesized. Despite ultralow thermal conductivity, the maximum thermoelectric figure‐of‐merit of the undoped sample was only zT=0.031 at 623 K, which was increased to 0.078 for the sample with the nominal composition of TlLa_1.95Ca_0.05Sb₃Se₉. These low values are a consequence of the uncompetitively low electrical conductivity.

中文翻译：

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铝锑酸镧TlLa2Sb3Se9的晶体结构和物理性质

合成了新的查库锑酸镧TlLa ₂ Sb ₃ Se _9，并确定了其晶体结构。TLLA ₂的Sb ₃硒_9个结晶在KLa的一个有序的变体₂的Sb ₃小号₉型，空间群P 2 ₁ 2 ₁ 2 ₁与晶格参数一个= 4.2621（2）埃，b = 15.155（5），c = 25.505（9）Å。TlLa ₂ Sb ₃ Se ₉的带隙计算出的Δε为0.47eV，并且实验确定为0.68eV。通过掺杂Ca ^2+可以优化其热电性能。合成了具有TlLa _2-x Ca _x Sb ₃ Se ₉（x = 0.01，0.03，0.05）组成的样品。尽管导热系数超低，但未掺杂样品的最大热电品质因数在623 K时仅为zT = 0.031，对于标称成分为TlLa _1.95 Ca _0.05 Sb ₃ Se ₉的样品，其最大热电系数为0.078 。这些低值是非竞争性低电导率的结果。