Oxygen-loss in A-site deficient Sr0.85La0.10TiO3 perovskite

Akin, Ipek; Li, Ming; Lu, Zhilun; Sinclair, Derek C.

doi:10.1039/c4ra04199b

Cited by 27 publications

(21 citation statements)

References 27 publications

(48 reference statements)

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“…It is also notable that many transition‐metal oxides consist of impurities (typically < 1%) in raw materials that may also affect the properties . Generally, low level of oxygen vacancies is present in BT, presumably due to the presence of impurities (such as Fe 3+ and Al 3+ ) in the TiO 2 reagents . Oxygen uptake can occur to fill the oxygen vacancies and create holes, given by Equation

{normalV}_{O}^{∙ ∙} + \frac{1}{2} {normalO}_{2} false(g false) \to {normalO}_{O}^{normalx} + 2 {normalh}^{∙}

…”

Section: Resultsmentioning

confidence: 99%

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Influence of A‐site nonstoichiometry on the electrical properties of BT‐BMT

Muhammad

Khesro

2016

J Am Ceram Soc

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A stoichiometric and 2 mol% Ba deficient samples in the formulation 0.5BaTiO3‐0.5BiMg1/2Ti1/2O3 (BT‐BMT) were processed via a mixed oxide solid‐state route. The deficient sample exhibited a high relative permittivity (2100±15%) over the temperature range 90‐450°C and a low dielectric loss (tanδ < 0.01), maintained up to high temperature (430°C). The samples exhibited intrinsic conduction mechanism and showed an n‐type character. By introducing 2 mol% Ba vacancies, a dramatic influence on the dielectric loss was observed which was mainly associated with the trapping of electrons by barium‐oxygen vacancy pair associated with the intentionally produced cation vacancies. Thus, control of composition by creating deficiency allows fine tuning of the dielectric properties of BT‐BMT ceramics for applications in high‐temperature multilayered ceramic capacitors.

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{normalV}_{O}^{∙ ∙} + \frac{1}{2} {normalO}_{2} false(g false) \to {normalO}_{O}^{normalx} + 2 {normalh}^{∙}

…”

Section: Resultsmentioning

confidence: 99%

“…39 Generally, low level of oxygen vacancies is present in BT, presumably due to the presence of impurities (such as Fe 3+ and Al 3+ ) in the TiO 2 reagents. 37,40,41 Oxygen uptake can occur to fill the oxygen vacancies and create holes, given by Equation (5)…”

Section: Ba Vacancies Induce Oxygen Vacancies ð2vmentioning

confidence: 99%

Influence of A‐site nonstoichiometry on the electrical properties of BT‐BMT

Muhammad

Khesro

2016

J Am Ceram Soc

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“…7. The A-cationic or anionic deficiency is commonly observed in cubic perovskites [32][33][34] but the B-site deficiency is rare in the cubic perovskites. This implies that it is energy-unfavorable to create the vacancies in the corner-shared octahedral sites in cubic perovskite structure.…”

Section: Resultsmentioning

confidence: 99%

Molten Salt Synthesis, Polymorphism, and Microwave Dielectric Properties of Ba₈NiTa₆O₂₄ Perovskite

Gong

Kuang

et al. 2015

J. Am. Ceram. Soc.

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Molten salt synthesis (MSS) of the eight‐layer hexagonal perovskite Ba8NiTa6O24 was performed using mixed KCl–NaCl salts in comparison with solid‐state synthesis (SSS). In the SSS, the hexagonal Ba8NiTa6O24 formed at 1300°C via a reaction between cubic Ba3NiTa2O9 and hexagonal Ba5Ta4O15. While the MSS did not lower the synthesis temperature of the hexagonal Ba8NiTa6O24 but stabilized an unusual A‐ and B‐site‐deficient cubic perovskite polymorph of Ba8NiTa6O24 below 1350°C as an intermediate phase prior to transforming into the hexagonal phase. This cubic polymorph contains ~3% A‐site and ~9.5% B‐site vacancies plus ~3% Ba cations in the B sites and demonstrated remarkable stability below 1350°C when without presence of the molten salt. The cubic polymorph displayed larger ε ~ 36 and τf ~ 110 ppm/°C than the hexagonal polymorph from the MSS (ε ~ 29 and τf ~ 67 ppm/°C). The hexagonal SSS‐processed ceramics showed advantageous dielectric properties (Qf ~ 52 000 GHz, τf ~ 30 ppm/°C) over both cubic and hexagonal MSS‐processed ones (Qf ~ 18 600–20 000 GHz), while displaying anisotropic grain growth. The anisotropic grain growth was suppressed significantly by the MSS processing.

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“…It has also been proposed that an internal barrier layer capacitor structure of conducting grains and insulating grain boundaries is responsible for the high effective permittivity in polycrystalline ceramics. The defect chemistry of Sr 0.85 La 0.10 TiO 3 perovskite oxide has been discussed based on chemical doping and oxygen‐loss mechanisms, and highlights the importance of A‐site vacancies on the oxygen‐loss mechanism in La‐doped ST‐based ceramics . In order to discover the origination of higher dielectric constant and dielectric loss in perovskite oxides, four kinds of selected microwave ceramics with higher dielectric constant of 180‐40 are investigated.…”

Section: Introductionmentioning

confidence: 99%

Complex impedance spectroscopy of perovskite microwave dielectric ceramics with high dielectric constant

et al. 2018

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The AC impedance of SrTiO3, Ca0.9Sr0.1TiO3, Ca0.7Sm0.2TiO3, and Ca0.7Sm0.3Ti0.7Al0.3O3 microwave dielectric ceramics with perovskite structures has been analyzed. The impedance spectroscopy results reveal the electrical properties of this series of samples vary significantly with the ceramic microstructure and electrical homogeneity. The εr values of grains for SrTiO3 and Ca0.9Sr0.1TiO3 ceramics are 193.8 and 138.1, respectively, confirming that dielectric response of the high‐εr microwave ceramics is contributed to the grains, at microwave frequencies. Impedance spectroscopy of Ca0.7Sm0.2TiO3 ceramic illustrates that electrical heterogeneous microstructures include interior grains and grain shells. The secondary phase existing in Ca0.7Sm0.2TiO3 ceramic causes deviation in bulk permittivity, resulting in a higher εr ~ 148 of grains than εr ~ 112 of bulk permittivity, measured at microwave frequencies. Grain and grain‐boundary impedance of Ca0.7Sm0.3Ti0.7Al0.3O3 ceramic cannot be separated completely. The permittivities of grains and grain boundaries in Ca0.7Sm0.3Ti0.7Al0.3O3 ceramic are εg ~ 17.8 and εgb ~ 20.8, and the combination of them is close to εr ~ 40 at microwave frequencies. The LogI−LogU curves of the ceramic system indicate that the conducting mechanism of grains and grain boundaries follows ohmic behavior.

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Oxygen-loss in A-site deficient Sr_0.85La_0.10TiO₃ perovskite

Abstract: Sintering temperature induces significant changes in bulk conductivity and activation energy, Ea of A-site deficient Sr0.85La0.10TiO3 due to oxygen loss.

Cited by 27 publications

References 27 publications

Influence of A‐site nonstoichiometry on the electrical properties of BT‐BMT

Influence of A‐site nonstoichiometry on the electrical properties of BT‐BMT

Molten Salt Synthesis, Polymorphism, and Microwave Dielectric Properties of Ba₈NiTa₆O₂₄ Perovskite

Complex impedance spectroscopy of perovskite microwave dielectric ceramics with high dielectric constant

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Oxygen-loss in A-site deficient Sr0.85La0.10TiO3 perovskite

Abstract: Sintering temperature induces significant changes in bulk conductivity and activation energy, Ea of A-site deficient Sr0.85La0.10TiO3 due to oxygen loss.

Cited by 27 publications

References 27 publications

Influence of A‐site nonstoichiometry on the electrical properties of BT‐BMT

Influence of A‐site nonstoichiometry on the electrical properties of BT‐BMT

Molten Salt Synthesis, Polymorphism, and Microwave Dielectric Properties of Ba8NiTa6O24 Perovskite

Complex impedance spectroscopy of perovskite microwave dielectric ceramics with high dielectric constant

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Oxygen-loss in A-site deficient Sr_0.85La_0.10TiO₃ perovskite

Molten Salt Synthesis, Polymorphism, and Microwave Dielectric Properties of Ba₈NiTa₆O₂₄ Perovskite