Tuning the thermoelectric properties of A-site deficient SrTiO3 ceramics by vacancies and carrier concentration.
Tuning the thermoelectric properties of A-site deficient SrTiO3 ceramics by vacancies and carrier concentration.
复制标题
DOI：
10.1039/c6cp05523k
复制
发表时间：
2016-09
期刊：
影响因子：
--
通讯作者：
D. Srivastava;C. Norman;F. Azough;M. Schäfer;E. Guilmeau;D. Kepaptsoglou;Q. Ramasse;G. Nicotra;R. Freer
中科院分区：
文献类型：
--
作者：
D. Srivastava;C. Norman;F. Azough;M. Schäfer;E. Guilmeau;D. Kepaptsoglou;Q. Ramasse;G. Nicotra;R. Freer
采用混合氧化物工艺制备了Sr0.8La0.067Ti0.8Nb0.203-δ系陶瓷。La1/3NbO_3组分产生∼13.4%的A位空位；这对所有样品都是固定的。粉末在1450-1700K的空气和还原条件下烧结；产品具有高密度(>；90%理论)。在还原条件下的处理导致了Ti1-xNbxO2-y第二相的形成，核壳结构和缺氧性。X-射线衍射仪证实为简单的立方结构，空间群为Pm~3[结合马克龙]m。透射电子显微镜显示高密度位错，而原子分辨分析扫描电子显微镜显示La，Nb和空位在晶格中均匀分布。X射线光电子能谱和热重分析表明，随着载流子浓度的增加，还原样品的缺氧量(δ值)为∼0.08，∼为2×1021 cm-3。载流子浓度和载流子迁移率都随着烧结时间的延长而增加，最大优值系数(ZT)为0.25。在没有额外A位空位的情况下，La或Nb的选择性额外掺杂导致了额外载流子的产生并降低了电阻率。这些都导致了在1000K时ZT值提高到0.345。氧空位和电荷载流子的贡献已经被单独研究过了。
Ceramics based on Sr0.8La0.067Ti0.8Nb0.2O3-δ have been prepared by the mixed oxide route. The La1/3NbO3 component generates ∼13.4% A-site vacancies; this was fixed for all samples. Powders were sintered under air and reducing conditions at 1450 to 1700 K; products were of high density (>90% theoretical). Processing under reducing conditions led to the formation of a Ti1-xNbxO2-y second phase, core-shell structures and oxygen deficiency. X-ray diffraction (XRD) confirmed a simple cubic structure with space group Pm3[combining macron]m. Transmission electron microscopy revealed a high density of dislocations while analytical scanning transmission electron microscopy at atomic resolution demonstrated a uniform distribution of La, Nb and vacancies in the lattice. X-ray photoemission spectroscopy and thermogravimetry showed the oxygen deficiency (δ value) to be ∼0.08 in reduced samples with enhanced carrier concentrations ∼2 × 1021 cm-3. Both carrier concentration and carrier mobility increased with sintering time, giving a maximum figure of merit (ZT) of 0.25. Selective additional doping by La or Nb, with no additional A site vacancies, led to the creation of additional carriers and reduced electrical resistivity. Together these led to enhanced ZT values of 0.345 at 1000 K. The contributions from oxygen vacancies and charge carriers have been investigated independently.