Influence of Ti-vacancies on the site occupancy of amphoteric calcium, oxygen vacancies, dielectric, optical, and ferroelectric behavior of Ba0.8Ca0.2Ti1-xO3-δ

IF 6.3 2区材料科学 Q2 CHEMISTRY, PHYSICAL

Journal of Alloys and Compounds Pub Date : 2024-12-16 DOI:10.1016/j.jallcom.2024.178115

Raz Muhammad, Asif Ali, Javier Camargo, Miriam S. Castro, Dandan Han

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引用次数: 0

Abstract

The defect chemistry of the amphoteric Ca²⁺ dopant in BaTiO₃ is a controversial issue, particularly regarding its site occupancy, solubility limit, and impact on material properties due to the charge compensation mechanism involved. In the present research work, the effect of intentionally produced Ti⁴⁺ vacancies was investigated on the structure and properties of Ba_0.8Ca_0.2Ti_1-xO_3-δ (x = 0.005, 0.01, 0.03, 0.05). A phase transition from ferro- to para-electric phase was observed with an increase in x. Raman spectroscopy revealed that Ca²⁺ also occupies the BO₆ octahedron by moving from A- to B-site. However, still oxygen vacancies (

V_{O}^{∙ ∙}

$V_{O}^{∙ ∙}$ ) exist due to lower oxidation of Ca²⁺ than Ti⁴⁺, supported by electron paramagnetic spectroscopy which revealed a signal at 2.004, associated with Ti deficiency, producing

V_{O}^{∙ ∙}

$V_{O}^{∙ ∙}$ . The grain growth was also inhibited (decreased from 11.4 μm to 1.36 μm) by the generation of vacancies which decreased the value of ε_r from 8085 to 1405 at T_c. These defects were also evident from the P-E loops which exhibited double hysteresis-like behavior, associated with defects in the material. The formation of

V_{O}^{∙ ∙}

$V_{O}^{∙ ∙}$ also greatly affected the optical band gap due to an increase in distortion in the structure. The band gap increased from 2.64 to 2.74 eV with an increase in x from 0.005 to 0.03. It was found that Ca²⁺ plays a vital role by shifting to B-site to reduce Ti-vacancies which affected the structure and properties of the Ba_0.8Ca_0.2TiO₃. The sample with the highest symmetry (x = 0.05) shows a slim double hysteresis loop and a remnant polarization of 0.85 μC/cm² at 50 kV/cm, which indicates its potential for use in high energy density applications.

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钛空位对 Ba0.8Ca0.2Ti1-xO3-δ 的两性钙、氧空位、介电、光学和铁电行为的影响

BaTiO3中两性Ca2+掺杂剂的缺陷化学性质是一个有争议的问题，特别是关于其位点占有率、溶解极限以及电荷补偿机制对材料性质的影响。在本研究工作中，研究了有意产生的 Ti4+ 空位对 Ba0.8Ca0.2Ti1-xO3-δ （x = 0.005、0.01、0.03、0.05）结构和性质的影响。拉曼光谱显示，Ca2+ 也从 A 位移动到 B 位，占据了 BO6 八面体。然而，由于 Ca2+ 的氧化程度比 Ti4+ 低，因此仍然存在氧空位（VO∙∙VO∙∙），电子顺磁谱也证实了这一点，该光谱显示在 2.004 处有一个信号，与 Ti 缺乏有关，产生了 VO∙∙VO∙∙。空位的产生也抑制了晶粒的生长（从 11.4 μm 减小到 1.36 μm），使εr 值在 Tc 时从 8085 降到 1405。这些缺陷在 P-E 循环中也很明显，P-E 循环表现出类似双磁滞的行为，这与材料中的缺陷有关。由于结构变形的增加，VO∙∙VO∙∙的形成也极大地影响了光带隙。当 x 从 0.005 增加到 0.03 时，带隙从 2.64 eV 增加到 2.74 eV。研究发现，Ca2+ 通过转移到 B 位来减少钛空位，从而影响了 Ba0.8Ca0.2TiO3 的结构和性质。对称性最高（x = 0.05）的样品显示出纤细的双磁滞环，在 50 kV/cm 时的残余极化为 0.85 μC/cm2，这表明它具有在高能量密度应用中使用的潜力。

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来源期刊

Journal of Alloys and Compounds 工程技术-材料科学：综合

CiteScore

11.10

自引率

14.50%

发文量

5146

审稿时长

67 days

期刊介绍： The Journal of Alloys and Compounds is intended to serve as an international medium for the publication of work on solid materials comprising compounds as well as alloys. Its great strength lies in the diversity of discipline which it encompasses, drawing together results from materials science, solid-state chemistry and physics.