Enhancement of Electrical Conduction and Phonon Scattering in Ga2O3(ZnO)9-In2O3(ZnO)9 Compounds by Modification of Interfaces at the Nanoscale
Enhancement of Electrical Conduction and Phonon Scattering in Ga2O3(ZnO)9-In2O3(ZnO)9 Compounds by Modification of Interfaces at the Nanoscale
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DOI：
10.1007/s11664-018-06878-w
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发表时间：
2019-04
影响因子：
2.1
通讯作者：
D. Alvarez-Ruiz;F. Azough;D. Hernández-Maldonado;D. Kepaptsoglou;Q. Ramasse;P. Švec;R. Freer
中科院分区：
文献类型：
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作者：
D. Alvarez-Ruiz;F. Azough;D. Hernández-Maldonado;D. Kepaptsoglou;Q. Ramasse;P. Švec;R. Freer
Ga_2O_3（ZnO）_9和In_2O_3（ZnO）_9同系相由于其层状结构作为热电氧化物而受到人们的关注。Ga_2O_3（ZnO）_9具有较低的热导率，而In_2O_3（ZnO）_9具有较高的电导率。研究了Ga_2O_3（ZnO）_9-In_2O_3（ZnO）_9固溶体的TE特性，并与晶体结构的变化进行了关联。以B2 O3和Nd 2 O3为添加剂，采用固相法制备了高质量的（1-x）Ga 2 O3（ZnO）9-（ZnO）9（x= 0.0 ~ 1.0）陶瓷。通过X射线衍射、高分辨率透射电子显微镜和原子分辨率扫描透射电子显微镜-高角度环形暗场成像-能量色散X射线光谱（STEM-HAADF-EDS）技术分析晶体结构。在（1−x）Ga 2 O3（ZnO）9-xIn 2 O3（ZnO）9系统的所有样品中观察到具有成分调制的层状超结构。所有的陶瓷表现出纳米级的结构特征，确定为Ga和In丰富的反转边界（IBs）。20摩尔%的取代度In（x= 0.2）在Ga 2 O3（ZnO）9化合物中生成通常在In 2 O3（ZnO）m系统中发现的基底和锥形铟IB。（Ga0.8In0.2）2 O3（ZnO）9化合物没有表现出Cmcm结构特征 Cmcm Ga 2 O3（ZnO）9化合物，它是由富Ga的IBs沿着纤锌矿ZnO的金字塔平面堆叠形成的，但其特征类似于由$ R\overline{3} m $$所展示的晶体结构。 R 3 ¯ M In_2O_3（ZnO）薄膜具有基底型和锥形型铟离子束。结构变化导致TE性能的改善。例如，（Ga0.8In0.2）2 O3（ZnO）9在900 K时的热导率为2 W/m K，功率因数为150μW/m K2，品质因数（ZT）为0.07。这是Ga 2 O3（ZnO）9基同系化合物的最高ZT，并且与In 2 O3（ZnO）9同系化合物的最高ZT相当。
The Ga2O3(ZnO)9and In2O3(ZnO)9homologous phases have attracted attention as thermoelectric (TE) oxides due to their layered structures. Ga2O3(ZnO)9exhibits low thermal conductivity, while In2O3(ZnO)9possesses higher electrical conductivity. The TE properties of the solid solution of Ga2O3(ZnO)9-In2O3(ZnO)9were explored and correlated with changes in the crystal structure. High-quality (1−x)Ga2O3(ZnO)9-(ZnO)9(x= 0.0 to 1.0) ceramics were prepared by the solid-state route using B2O3and Nd2O3as additives. The crystal structures were analysed by x-ray diffraction, high-resolution transmission electron microscopy and atomic resolution scanning transmission electron microscopy–high-angle annular dark field imaging–energy dispersive x-ray spectroscopy (STEM–HAADF–EDS) techniques. A layered superstructure with compositional modulations was observed in all samples in the (1−x)Ga2O3(ZnO)9-xIn2O3(ZnO)9system. All the ceramics exhibited nanoscale structural features identified as Ga- and In-rich inversion boundaries (IBs). Substitution of 20 mol.% In (x= 0.2) in the Ga2O3(ZnO)9compounds generated basal and pyramidal indium IBs typically found in the In2O3(ZnO)msystem. The (Ga0.8In0.2)2O3(ZnO)9compound does not exhibit the structural features of the $$ Cmcm $$ Cmcm Ga2O3(ZnO)9compound, which is formed by a stacking of Ga-rich IBs along the pyramidal plane of the wurtzite ZnO, but features that resemble the crystal structure exhibited by the $$ R\overline{3} m $$ R 3 ¯ m In2O3(ZnO)mwith basal and pyramidal indium IBs. The structural changes led to improved TE performance. For example, (Ga0.8In0.2)2O3(ZnO)9showed a low thermal conductivity of 2 W/m K and a high power factor of 150μW/m K2giving a figure of merit (ZT) of 0.07 at 900 K. This is the highest ZT for Ga2O3(ZnO)9-based homologous compounds and is comparable with the highest ZT reported for In2O3(ZnO)9homologous compounds.