Abstract Highly sodium deficient Na0.6NbO3 (NN) ceramics were prepared and characterized. Their mean structure could be described by a mixture of the predominant P polymorph (S.G. Pbma) and the Q phase (S.G. P21ma), at room temperature, as deduced from Rietveld refinements of Powder X-ray diffraction and Raman scattering data. Besides, microstructural and compositional heterogeneity was evidenced from HRTEM and XPS analyses. Dielectric measurements on this highly vacancies-containing NN material indicated a hysteretic transition taking place at ~12 and −18 °C on the heating and cooling regimes, respectively. This means a considerable shift to lower temperatures of the transition temperatures concerning the P/Q transformations previously described for the NaNbO3 material. At an intermediate frequency of 10 kHz, maximum permittivity and tangent loss values of e' = 1250 and tgδ = 2 were obtained on heating, whereas lower values of e' = 65 and tgδ = 0.04 were displayed on cooling regime. These anomalies were interpreted in terms of ferrolectric-antiferroelectric-paralectric phase-transitions implying a PTCR behavior within certain temperature range. This response, observed in this complex material for the first time, has interesting implications for the possible application of NN ceramics in sensing and dielectric materials fields.

中文翻译：

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A 位高度缺乏 NaxNbO3 电陶瓷中的新介电异常

摘要 制备并表征了高度缺钠的Na0.6NbO3（NN）陶瓷。根据粉末 X 射线衍射和拉曼散射数据的 Rietveld 细化推断，它们的平均结构可以在室温下通过主要 P 多晶型物 (SG Pbma) 和 Q 相 (SG P21ma) 的混合物来描述。此外，HRTEM 和 XPS 分析证明了微观结构和成分的异质性。对这种高度含空位的 NN 材料的介电测量表明，在加热和冷却状态下，分别在 ~12 和 -18°C 发生了滞后转变。这意味着与先前针对 NaNbO3 材料描述的 P/Q 转变相关的转变温度向较低温度的显着转变。在 10 kHz 的中频，e' = 1250 和 tgδ = 2 的最大介电常数和切线损耗值是在加热时获得的，而 e' = 65 和 tgδ = 0.04 的较低值在冷却状态下显示。这些异常被解释为铁电-反铁电-顺电相变，这意味着在特定温度范围内的 PTCR 行为。首次在这种复杂材料中观察到的这种响应对 NN 陶瓷在传感和介电材料领域的可能应用具有重要意义。