Unusual effects of post annealing on optical and dielectric properties of (Nb_0.5In_0.5)_0.01Ti_0.99O₂ (NITO-1.0%) are reported in the present study. The post-annealing performed under embedding in Al₂O₃ powder changes the color of a NITO-1.0% single crystal from black to yellow. Furthermore, the apparent increase in the relative permittivity due to the Maxwell–Wagner–Sillars effect, on the order of 10⁴, observed in the as-synthesized NITO-1.0% completely disappears after the post-annealing to reveal an intrinsic enhancement of dielectric response due to the co-doping of Nb and In. The relative permittivity of the post-annealed NITO-1.0% uniformly increases by approximately 120 from the original value of pure-TiO₂ over a wide temperature range from 4.2 K to room temperature. A temperature dependence of permittivity in the post-annealed NITO-1.0% shows behavior that is qualitatively identical to that of pure TiO₂, indicating that the co-doping gives rise to an additional dielectric response in TiO₂, probably through creation of defect complexes with large polarizability. The polarizability of the defect complex is estimated to be two hundred times greater than that of Ti⁴⁺, giving a new insight for the design of novel dielectric materials with large permittivity by means of complex defect engineering.

中文翻译：

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“黄色”（Nb + In）共掺杂TiO2的介电常数提高

在本研究中报告了后退火对（Nb _0.5 In _0.5）_0.01 Ti _0.99 O ₂（NITO-1.0％）的光学和介电性能的异常影响。在嵌入Al ₂ O ₃粉末中进行的后退火将NITO-1.0％单晶的颜色从黑色变为黄色。此外，由于麦克斯韦-瓦格纳-西勒斯效应，相对介电常数明显增加，约为10 ⁴在合成后的NITO-1.0％中观察到的Nb，在退火后完全消失，以揭示由于Nb和In的共掺杂导致介电响应的内在增强。在从4.2 K到室温的宽温度范围内，退火后的NITO-1.0％的相对介电常数从纯TiO ₂的原始值均匀增加大约120 。后退火的NITO-1.0％中介电常数的温度依赖性显示出与纯TiO ₂在质量上相同的行为，表明共掺杂在TiO _2中引起了额外的介电响应，可能是通过创建具有大极化率的缺陷复合物。缺陷复合物的极化率估计是Ti ^4+的200倍，这为通过复杂缺陷工程设计具有大介电常数的新型介电材料提供了新的见识。