Characterizations of structural, optical, and dielectric properties of oxynitride perovskites ACa0.2M0.8O2.6N0.4 (A= Sr, Ba; M = Nb, Ta)

IF 9.1 2区化学 Q1 CHEMISTRY, INORGANIC & NUCLEAR Progress in Solid State Chemistry Pub Date : 2024-03-01 DOI:10.1016/j.progsolidstchem.2024.100439

Jae Won Seol , Jong-Sook Lee , Maxim Avdeev , Young-Il Kim

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Abstract

Perovskite-type oxynitrides ACa_0.2M_0.8O_2.6N_0.4 (A = Sr, Ba; M = Nb, Ta) were synthesized via the ammonolytic reaction between A₅M₄O₁₅ and CaCl₂, where the Ca²⁺ insertion and O²⁻/N³⁻ substitution occurred cooperatively. In terms of the average structure, SrCa_0.2Nb_0.8O_2.6N_0.4 and SrCa_0.2Ta_0.8O_2.6N_0.4 belong to the orthorhombic Pnma space group, and BaCa_0.2Nb_0.8O_2.6N_0.4 and BaCa_0.2Ta_0.8O_2.6N_0.4, the primitive cubic Pm $\overline{3}$ m group. The comparison between the experimental lattice volume and the summed ionic volume suggested that ACa_0.2M_0.8O_2.6N_0.4 have higher degrees of ionicity than AM'_0.2M_0.8O_3−xN_x (M′ = Li, Mg, Mn), but are more covalent than ANa_0.2M_0.8O_2.8N_0.2. Despite the significant mismatches of size and charge between Ca²⁺ and Nb⁵⁺ (or Ta⁵⁺), no cation ordering was detected on the octahedral site. On the other hand, the O/N distribution appeared to depend on the bonding geometry around the anion sites in a way N favors the straighter bonding connectivity of M−N−M. The band gap energies of ACa_0.2M_0.8O_2.6N_0.4 were estimated to be 1.9–2.25 eV depending on A and M. The band gaps and color properties of AMO₂N and AM'_0.2M_0.8O_3−xN_x (A = Sr, Ba; M = Nb, Ta; M′ = Li, Na, Mg, Ca, Mn) are compared. Thermogravimetry and differential scanning calorimetry were conducted in the air to assess the oxynitride stability. The electrical behaviors were studied by the equivalent circuit analysis of the impedance spectrum using compacted polycrystalline specimens, where BaCa_0.2Ta_0.8O_2.6N_0.4 was found to possess a bulk dielectric constant of 4550 along with an electrical conductivity of ≈10⁻⁶ S/cm at 27 °C. It remains, however, necessary to assess the extrinsic effects arising from the non-ideal sintering to interpret thoroughly the electrical property of BaCa_0.2Ta_0.8O_2.6N_0.4.

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氧化氮化物包晶 ACa0.2M0.8O2.6N0.4（A= Sr、Ba；M= Nb、Ta）的结构、光学和介电特性表征

通过 A5M4O15 与 CaCl2 的氨解反应合成了 Perovskite 型氧氮化物 ACa0.2M0.8O2.6N0.4（A = Sr、Ba；M = Nb、Ta），其中 Ca2+ 插入和 O2-/N3- 取代协同发生。从平均结构来看，SrCa0.2Nb0.8O2.6N0.4 和 SrCa0.2Ta0.8O2.6N0.4 属于正方 Pnma 空间群，BaCa0.2Nb0.8O2.6N0.4 和 BaCa0.2Ta0.8O2.6N0.4 属于原始立方 Pm 3‾m 空间群。实验晶格体积与离子体积总和的比较表明，ACa0.2M0.8O2.6N0.4 的离子度高于 AM'0.2M0.8O3-xNx（M′= Li、Mg、Mn），但共价度高于 ANa0.2M0.8O2.8N0.2。尽管 Ca2+ 和 Nb5+（或 Ta5+）之间的尺寸和电荷存在明显的不匹配，但在八面体位点上没有检测到阳离子有序化。另一方面，O/N 分布似乎取决于阴离子位点周围的成键几何形状，而 N 有利于 M-N-M 的较直成键连接。根据 A 和 M 的不同，ACa0.2M0.8O2.6N0.4 的带隙能估计为 1.9-2.25 eV。比较了 AMO2N 和 AM'0.2M0.8O3-xNx（A = Sr、Ba；M = Nb、Ta；M′ = Li、Na、Mg、Ca、Mn）的带隙和颜色特性。在空气中进行了热重分析和差示扫描量热分析，以评估氮氧化物的稳定性。通过对压制多晶试样的阻抗谱进行等效电路分析，研究了其电学行为，发现 BaCa0.2Ta0.8O2.6N0.4 在 27 °C 时的体介电常数为 4550，电导率为 ≈10-6 S/cm。然而，要彻底解释 BaCa0.2Ta0.8O2.6N0.4 的电气特性，仍有必要评估非理想烧结产生的外在影响。

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来源期刊

Progress in Solid State Chemistry 化学-无机化学与核化学

CiteScore

14.10

自引率

3.30%

发文量

期刊介绍： Progress in Solid State Chemistry offers critical reviews and specialized articles written by leading experts in the field, providing a comprehensive view of solid-state chemistry. It addresses the challenge of dispersed literature by offering up-to-date assessments of research progress and recent developments. Emphasis is placed on the relationship between physical properties and structural chemistry, particularly imperfections like vacancies and dislocations. The reviews published in Progress in Solid State Chemistry emphasize critical evaluation of the field, along with indications of current problems and future directions. Papers are not intended to be bibliographic in nature but rather to inform a broad range of readers in an inherently multidisciplinary field by providing expert treatises oriented both towards specialists in different areas of the solid state and towards nonspecialists. The authorship is international, and the subject matter will be of interest to chemists, materials scientists, physicists, metallurgists, crystallographers, ceramists, and engineers interested in the solid state.