Effect of oxygen vacancies on SrTiO  electrical properties

Trabelsi, H.; Bejar, M.; Dhahri, E.; Sajieddine, M.; Khirouni, K.; Prezas, P.R.; Melo, B. M. G.; Valente, M.A.; Graça, M.P.F.

doi:10.1016/j.jallcom.2017.06.313

Cited by 69 publications

(16 citation statements)

References 38 publications

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“…7), which is consistent with dielectric relaxation in this region. These results are generally consistent with trends observed in experimental measurements of SrTiO 3 dielectric materials [48,49]. DFT calculations have shown that oxygen vacancies represent a major factor in the increase of dielectric permittivity in non-stoichiometric SrTiO 3 .…”

Section: Nature Of Dielectric Permittivitysupporting

confidence: 90%

Point defects and their effect on dielectric permittivity in strontium titanate ceramics

et al. 2021

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The origin of dielectric properties of strontium titanate ceramics is investigated using DFT calculations in periodic system. It was determined that the main factors contributing to the increase in dielectric permittivity are: tetragonal distortion of the normally cubic lattice, and charge imbalance induced displacement of titanium center from its central position. Oxygen vacancies were determined to create significantly larger effects than other types of vacancies, like Ti and SrO. The extent of tetragonal distortion was found to be determined by oxygen vacancy distribution, rather than total concentration: relatively symmetrical distribution of oxygen vacancies resulted in smaller tetragonal distortion of the lattice, and, consequently, smaller increase in dielectric permittivity. Charge imbalance naturally destabilizes the cubic lattice, forcing the Ti-atom out of its central position, resulting in tetragonal lattice with increased dielectric permittivity. The process stabilizes the strontium titanate lattice, while increasing the c/a ratio. Therefore, the dielectric permittivity of strontium titanate can be increased by changes to the system that increase tetragonal distortion of the lattice and/or introduce additional negative charge.

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Section: Nature Of Dielectric Permittivitysupporting

confidence: 90%

Point defects and their effect on dielectric permittivity in strontium titanate ceramics

et al. 2021

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“…5 (d)) this peak appears near to 100 kHz. For the maximum of peak observed in Z" spectrum is observed a shift for higher values with increasing of the temperature what can be related to the relaxation process thermally activated [50]. As can be seen in insets of Fig.…”

Section: Resultsmentioning

confidence: 51%

“…where f Max is the frequency when Z" has a maximum value, f o is the pre-exponential term, E a is the activation energy of the process, K b is the Boltzmann constant and T is temperature [50]. The E a are determined by the angular coefficient of linear curves in Nyquist's plots (Z" versus Z') were also analyzed.…”

Section: Resultsmentioning

confidence: 99%

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Effect of Bi2O3-B2O3 as a Sintering aid in Microstructure and Dielectric Properties of Fe2Mo3O12 Electroceramic.

Araújo¹,

Silva²,

Pereira³

et al. 2020

Preprint

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Molybdates from A2Mo3O12 family have been widely investigated due to its low sintering temperature, low thermal expansion coefficient, and low dielectric loss. Fe2Mo3O12 (FMO) is an oxide from this family and widely used in the catalytic field. The aim of this work is to evaluate the influence of the Bi2O3-B2O3 as a sintering aid in the microstructure and dielectric properties of FMO. The diffraction results showed that the FMO with the monoclinic structure phase was obtained after the calcination process (650 °C). Mössbauer spectroscopy showed the formation of Fe2O3 after the sintering process at 800 °C. The scanning electron-microscopic demonstrates an increase of the grain as a function of sintering aid concentration. The samples were analyzed by using the impedance spectroscopy at radiofrequency with temperature variation. The Nyquist diagram obtained in this temperature range was fitted from an equivalent circuit with three R-CPE associations, corresponding to the morphology of the electroceramics. For dielectric properties in the microwave, all the samples showed values of εr lower than 10. Values of Q x f above 14132.35 GHz were achieved. The thermal stability was evaluated by the temperature coefficient of resonant frequency (τf). The lowest τf values of -6.55 ppm/°C and -4.35 ppm/°C (near-zero) were measured to FMO and FMO mixed with 7.5 wt% Bi2O3-B2O3, respectively. Based on these results, FMO can be used to low permittivity ceramic for low temperature co-fired ceramics (LTCC) applications, antenna substrate, and millimeter-wave range.

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“…8. This indicates enhanced mobile charge hopping in the grain boundaries and sample-electrode interfaces [35,60]. The interfacial charges can produce a thin conductive layer at the sample surface effectively reducing the resistivity at high frequencies.…”

Section: F Resistivity Measurementsmentioning

confidence: 99%

Room temperature ferroic orders in Zr and (Zr, Ni) doped SrTiO$_3$

Ahmed¹,

Faysal²,

Khan³

et al. 2021

Preprint

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We synthesized strontium titanate SrTiO3 (STO), Zr doped Sr1-xZrxTiO3 and (Zr, Ni) co-doped Sr1-xZrxTi1-yNiyO3 samples using solid state reaction technique to report their structural, electrical and magnetic properties. The cubic P m-3m phase of the synthesized samples has been confirmed using Rietveld analysis of the powder X-ray diffraction pattern. The grain size of the synthesized materials was reduced significantly due to Zr doping as well as (Zr, Ni) co-doping in STO. The chemical species of the samples were identified using energy-dispersive X-ray spectroscopy. We observed forbidden first order Raman scattering at 148, 547 and 797 cm −1 which may indicate nominal loss of inversion symmetry in cubic STO. The absence of absorption at 500 cm −1 and within 600-700 cm −1 band in Fourier Transform Infrared spectra corroborates Zr and Ni as substitutional dopants in our samples. Due to 4% Zr doping in Sr0.96Zr0.04TiO3 sample dielectric constant, remnant electric polarization, remnant magnetization and coercivity were increased. Notably, in the case of 4% Zr and 10% Ni co-doping we have observed clearly the existence of both FE and FM hysteresis loops in Sr0.96Zr0.04Ti0.90Ni0.10O3 sample. In this co-doped sample, the remnant magnetization and coercivity were increased by ∼1 and ∼2 orders of magnitude respectively as compared to those of undoped STO. The coexistence of FE and FM orders in (Zr, Ni) co-doped STO might have the potential for interesting multiferroic applications.

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Effect of oxygen vacancies on SrTiO electrical properties

Cited by 69 publications

References 38 publications

Point defects and their effect on dielectric permittivity in strontium titanate ceramics

Point defects and their effect on dielectric permittivity in strontium titanate ceramics

Effect of Bi2O3-B2O3 as a Sintering aid in Microstructure and Dielectric Properties of Fe2Mo3O12 Electroceramic.

Room temperature ferroic orders in Zr and (Zr, Ni) doped SrTiO$_3$

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