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Na-doping enables both dislocations and holes in EuMg2Sb2 for thermoelectric enhancements
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2020-04-03 , DOI: 10.1039/d0ta02081h Cheng Sun 1, 2, 3, 4, 5 , Wen Li 1, 2, 3, 4, 5 , Xuemin Shi 1, 2, 3, 4, 5 , Zhonglin Bu 1, 2, 3, 4, 5 , Pengfei Nan 5, 6, 7, 8 , YunYun Li 3, 5, 9, 10, 11 , Binghui Ge 5, 6, 7, 8 , Yanzhong Pei 1, 2, 3, 4, 5
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2020-04-03 , DOI: 10.1039/d0ta02081h Cheng Sun 1, 2, 3, 4, 5 , Wen Li 1, 2, 3, 4, 5 , Xuemin Shi 1, 2, 3, 4, 5 , Zhonglin Bu 1, 2, 3, 4, 5 , Pengfei Nan 5, 6, 7, 8 , YunYun Li 3, 5, 9, 10, 11 , Binghui Ge 5, 6, 7, 8 , Yanzhong Pei 1, 2, 3, 4, 5
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A high conduction band degeneracy (Nv = 6) leads to an extraordinary figure of merit (zT) in n-type Mg3Sb2 thermoelectrics, while the p-type ones show a much inferior zT due to its lower Nv of only 1 owing to the large energy offset (ΔE ∼ 0.4 eV) between the two valence bands. The derivatives of Mg3Sb2, ternary AB2C2 (A = Eu, Yb, Ca, Sr, Ba; B = Mg, Zn, Cd; C = Sb, Bi) Zintls, show a similar valence band structure but with a much smaller ΔE of <0.2 eV, leading to potential convergence of both valence bands for a high overall Nv of 3. This band feature promotes AB2C2 ternaries to be potential p-type thermoelectrics matching with n-type Mg3Sb2 for efficient thermoelectric applications, thus motivating the current work focusing on p-type EuMg2Sb2 thermoelectrics. Interestingly, Na-doping at the Eu site is found to be particularly effective for creating dense in-grain dislocations, which results in a remarkable reduction in lattice thermal conductivity to ∼0.5 W m−1 K−1. Moreover, Na-doping increases the hole concentration up to 6.0 × 1019 cm−3, leading to an effective involvement of multiple transporting valence bands. The synergistic effects of dense dislocations and multi-band transport, both enabled by Na-doping, led EuMg2Sb2 to show the highest zT among known doped p-type ternary AMg2C2 Zintl thermoelectrics.
中文翻译：
钠掺杂可实现EuMg2Sb2中的位错和空穴，从而增强热电性能
高导带简并性（N v = 6）导致n型Mg 3 Sb 2热电材料具有非凡的品质因数（zT），而p型由于其较低的N v而显示出差得多的zT。 1由于较大的能量偏移量（Δ Ë两个价带之间〜0.4电子伏特）。Mg 3 Sb 2，三元AB 2 C 2（A = Eu，Yb，Ca，Sr，Ba; B = Mg，Zn，Cd; C = Sb，Bi）Zintls的衍生物显示相似的价带结构，但具有ΔE小得多小于0.2 eV，导致两个价带的潜在会聚，从而使N v达到较高的3。此能带特征促使AB 2 C 2三元成为与n型Mg 3 Sb 2匹配的潜在p型热电，从而实现高效热电应用，从而激发了当前致力于p型EuMg 2 Sb 2热电学的工作。有趣的是，发现Eu位置的Na掺杂对于产生致密的晶粒内位错特别有效，这导致晶格热导率显着降低至〜0.5 W m -1 K -1。此外，Na掺杂使空穴浓度增加到6.0×10 19 cm -3，导致有效地涉及多个传输价带。Na掺杂使致密位错和多带传输的协同效应使EuMg 2 Sb 2在已知的掺杂p型三元AMg 2 C 2 Zintl热电器件中显示出最高的zT。
更新日期：2020-04-24
中文翻译：
钠掺杂可实现EuMg2Sb2中的位错和空穴，从而增强热电性能
高导带简并性（N v = 6）导致n型Mg 3 Sb 2热电材料具有非凡的品质因数（zT），而p型由于其较低的N v而显示出差得多的zT。 1由于较大的能量偏移量（Δ Ë两个价带之间〜0.4电子伏特）。Mg 3 Sb 2，三元AB 2 C 2（A = Eu，Yb，Ca，Sr，Ba; B = Mg，Zn，Cd; C = Sb，Bi）Zintls的衍生物显示相似的价带结构，但具有ΔE小得多小于0.2 eV，导致两个价带的潜在会聚，从而使N v达到较高的3。此能带特征促使AB 2 C 2三元成为与n型Mg 3 Sb 2匹配的潜在p型热电，从而实现高效热电应用，从而激发了当前致力于p型EuMg 2 Sb 2热电学的工作。有趣的是，发现Eu位置的Na掺杂对于产生致密的晶粒内位错特别有效，这导致晶格热导率显着降低至〜0.5 W m -1 K -1。此外，Na掺杂使空穴浓度增加到6.0×10 19 cm -3，导致有效地涉及多个传输价带。Na掺杂使致密位错和多带传输的协同效应使EuMg 2 Sb 2在已知的掺杂p型三元AMg 2 C 2 Zintl热电器件中显示出最高的zT。
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