Half-Heusler compounds usually exhibit relatively higher lattice thermal conductivity that is undesirable for thermoelectric applications. Here we demonstrate by first-principles calculations and Boltzmann transport theory that the BiBaK system is an exception, which has rather low thermal conductivity as evidenced by very small phonon group velocity and relaxation time. Detailed analysis indicates that the heavy Bi and Ba atoms form a cage-like structure, inside which the light K atom rattles with larger atomic displacement parameters. In combination with its good electronic transport properties, the BiBaK shows a maximum n-type ZT value of 1.9 at 900 K, which outperforms most half-Heusler thermoelectric materials.

中文翻译：

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具有本质低晶格热导率的半霍斯勒化合物 BiBaK 的高热电性能


半霍斯勒化合物通常表现出相对较高的晶格导热率，这对于热电应用来说是不期望的。在这里，我们通过第一性原理计算和玻尔兹曼输运理论证明，BiBaK 系统是一个例外，它具有相当低的热导率，非常小的声子群速度和弛豫时间证明了这一点。详细分析表明，重Bi和Ba原子形成笼状结构，轻K原子在其内部以较大的原子位移参数振动。结合其良好的电子传输特性，BiBaK 在 900 K 时表现出最大 n 型 ZT 值为 1.9，优于大多数 half-Heusler 热电材料。