A and B site doping of a phonon-glass perovskite oxide thermoelectric
A and B site doping of a phonon-glass perovskite oxide thermoelectric
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DOI：
10.1039/c8ta03739f
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发表时间：
2018-08-28
影响因子：
11.9
通讯作者：
Rosseinsky, M. J.
中科院分区：
文献类型：
--
作者：
Daniels, L. M.;Ling, S.;Rosseinsky, M. J.
通过调节A位阳离子的大小，可以控制八面体畸变的程度，并最终控制新的钙钛矿固溶体La0.5Na0.5-xKxTiO 3中的结构对称性，当x增加到0.4以上时，提供菱形到立方的转变。La 3+和K+离子随机分布在A位上，导致立方La0.5K0.5TiO 3（Pm（3）over barm）中声子无序，在300 K时，声子玻璃的热导率为2.37（12）W m（-1）K-1，与同结构SrTiO 3相比，降低了75%。Sr 2+对La 3+和K+的这种简单阳离子取代保持了钙钛矿结构的灵活结构化学，并且探索了用于引入电子电荷载流子的两种掺杂机制：La 1-yKyTiO 3中的A位点掺杂或La 0.5K0.5Ti 1-zNbzO 3中的B位点掺杂。通过这两种机制掺杂后，La0.5K0.5TiO3的声子玻璃热导率得以保留，这两种机制突出了通常强烈耦合的热和电子传输如何通过钙钛矿中的质量无序而最小化。在具有菱面体（R3 c）对称性的A位掺杂的La 1-yKyTiO 3中，对八面体畸变的精确控制提供了比在保持未掺杂的La 0.5K 0.5TiO 3母体的立方（Pm（3）over barm）对称性的B位掺杂的La 0.5K 0.5Ti 1-zNbzO 3中实现的更低的带色散和增加的载流子有效质量。与B位掺杂的机制相比，A位掺杂的La 1-yKyTiO 3的更高的Seebeck系数产生更大的功率因数，并导致热电优值增加和转换效率提高。
By tuning the A site cation size it is possible to control the degree of octahedral distortion and ultimately structural symmetry in the new perovskite solid solution La0.5Na0.5-xKxTiO3, affording a rhombohedral-to-cubic transition as x increases above 0.4. The La3+ and K+ cations are distributed randomly across the A site leading to significant phonon disorder in cubic La0.5K0.5TiO3 (Pm (3) over barm) which produces a phonon-glass with a thermal conductivity of 2.37(12) W m(-1) K-1 at 300 K; a reduction of 75% when compared with isostructural SrTiO3. This simple cation substitution of Sr2+ for La3+ and K+ maintains the flexible structural chemistry of the perovskite structure and two mechanisms of doping for the introduction of electronic charge carriers are explored; A site doping in La1-yKyTiO3 or B site doping in La0.5K0.5Ti1-zNbzO3. The phonon-glass thermal conductivity of La0.5K0.5TiO3 is retained upon doping through both of these mechanisms highlighting how the usually strongly coupled thermal and electronic transport can be minimised by mass disorder in perovskites. Precise control over octahedral distortion in A site doped La1-yKyTiO3, which has rhombohedral (R3c) symmetry affords lower band dispersions and increased carrier effective masses over those achieved in B site doped La0.5K0.5Ti1-zNbzO3 which maintains the cubic (Pm (3) over barm) symmetry of the undoped La0.5K0.5TiO3 parent. The higher Seebeck coefficients of A site doped La1-yKyTiO3 yield larger power factors and lead to increased thermoelectric figures of merit and improved conversion efficiencies compared with the mechanism for B site doping.