Barium Strontium Titanate Ceramics Research Articles

Investigation of Ga–Nb co-doped barium strontium titanate ceramics for DC-bias free dielectrics

The Ba0.8Sr0.2Ti1−2x Ga x Nb x O3 (0 ≤ x ≤ 0.10) ceramics were fabricated and the electrical properties were evaluated regarding DC-bias and temperature characteristics of the dielectric properties. The ceramics with x = 0.10 exhibited a stable dielectric constant with a change of–40% within 25 °C–150 °C. The dielectric loss of all the co-doped ceramics was below 2% within 25 °C–200 °C. The Ba0.8Sr0.2Ti1−2x Ga x Nb x O3 ceramics showed a higher dielectric constant with a lower DC-bias dependence as compared to previous study on co-doped BaTiO3 ceramics. The Ba0.8Sr0.2Ti0.20Ga0.10Nb0.10O3 ceramics exhibited the best results of DC-bias dependence ≈−24%, dielectric constant at 100 kV cm−1 ≈ 560, and the dielectric constant at 0 kV cm−1 ≈ 735. The better results for the Ga–Nb co-doped BST ceramics might be due to the higher contribution of the ionic polarization in the BST base matrix resulting in a shallower potential energy curve.

Improved multiferroic and magnetodielectric properties in Ni and Fe co-doped barium strontium titanate ceramics

Improved multiferroic and magnetodielectric properties in Ni and Fe co-doped barium strontium titanate ceramics

Giant dielectric tunability in ferroelectric ceramics with ultralow loss by ion substitution design

Due to their responsiveness to modulation by external direct current fields, dielectric tunable materials are extensively utilized in integrated components, such as ferroelectric phase shifters. Barium strontium titanate ceramics have been considered the most potential tunable materials for a long time. However, the significant dielectric loss and high voltage drive have limited their further applications. Recently, Bi6Ti5WO22 ceramic has regained attention for its high dielectric tunability with low loss. In this study, we judiciously introduce Nb5+ with a larger ionic radius, replacing Ti4+ and W6+. This successful substitution enables the modulation of the phase transition temperature of Bi6Ti5WO22 ceramics to room temperature, resulting in superior tunable properties. Specifically, the 0.7Bi6Ti5WO22−0.3Bi6Ti4Nb2O22 ceramics exhibit giant tunability (~75.6%) with ultralow loss (<0.002) under a low electric field (1.5 kV/mm). This tunability is twice that of barium strontium titanate ceramics with a similar dielectric constant and only one-tenth of the loss. Neutron powder diffraction and transmission-electron-microscopy illustrate the nanodomains and micro-strains influenced by ion substitution. Density functional theory simulation calculations reveal the contribution of ion substitution to polarization. The research provides an ideal substitute for tunable material and a general strategy for adjusting phase transition temperature to improve dielectric properties.

Enhanced structural, magnetodielectric, and multiferroic response in Fe and Co Co-doped Barium strontium titanate ceramics

In this paper, the ambient temperature multiferroic effect resulting from the incorporation of transition metal ions (Fe3+ and Co2+) in lead-free BST [ Ba0.7Sr0.3(Fex/2Cox/2)Ti1−xO3;x=0,0.01,0.03,0.05,0.07 ] ceramics synthesized via the solid-state reaction (SSR) procedure has been thoroughly analyzed. The investigation consistently scrutinized the effects of augmenting transition metal co-doping on the structural, ferroelectric, dielectric, magnetic, and magnetodielectric characteristics. The x-ray diffraction (XRD) patterns for all ceramic compositions demonstrated the formation of a monophasic (P4mm) crystalline structure. The Raman analysis evidenced the presence of various modes, which are associated with the occurrence of the single-phase and provide strong corroboration for the x-ray diffraction observations. Scanning electron micrographs reveals that the inclusion of transition metal ions results in the diminution of grain size. The frequency-dependent dielectric characteristics were represented over the frequency range of 1 kHz to 1 MHz. The P-E hysteresis curves demonstrate a consistent reduction in the values of Ps and Pr, whereas, the M-H curve reveals the enhancement in magnetic properties with increased doping. The magnetodielectric analysis confirmed the interplay between the ferroelectric and ferromagnetic ordering. The BST-1CF sample exhibited the highest MC % value of 5.30% along with the magnetoelectric coupling coefficient ‘γ’ of −6.01×10−1(memu/g)−2, making it a favorable entrant for the advancement of innovative non-volatile multiferroic memory gadgets.

Influence of thermal cycling rate and sintering temperature of barium titanate and barium strontium titanate ceramics on their dielectric properties

One of the negative effects of ferroelectric applications, particularly for electrocaloric effect (ECE) applications, is temperature hysteresis (ΔT Hyst). Temperature hysteresis is the difference between the temperatures corresponding to the maximum dielectric permittivity in heating and cooling modes. The value of ΔT Hyst is commensurate with the value of the ECE temperature change. The ECE is a phenomenon in which a material shows a reversible temperature change under an applied electric field. The aim of this work is to study the possibilities of temperature hysteresis reduction by varying the ceramic sintering temperature, changing the stoichiometry of BaxSr1-xTiO3 solid solutions, and changing the rate of the heating-cooling cycle.

Preparation of BST Powders and Ceramics via a Hybrid Method

Barium strontium titanate (Ba0.8Sr0.2TiO3; BST) ceramics, were prepared by the hybrid method between Solid-state reaction (SSR) and Sol-gel methods (SG) in a ratio of 1:0.1–1:0.5. The BST powder was successfully calcined at 850 °C for 2 h. This temperature is much lower than the calcination temperatures of the SSR method. The BST ceramics were sintered between 1150 and 1450 °C. All samples showed the pure perovskite structure corresponding to JCPDS no. 34-0411. The optimum sintering temperature was observed from the samples sintered at 1450 °C for 4 h, indicating a density of 5.26 g/cm3, dielectric constant of 7018, and ferroelectric properties: (P max = 13.8 μC/cm2, P r = 2.5 μC/cm2 and E c = 2.3 kV/cm at 30 kV/cm).

Synthesis and characterization of ferroelectric Barium strontium titanate Ceramics

Synthesis and characterization of ferroelectric Barium strontium titanate Ceramics

Spin and valence variation in cobalt doped barium strontium titanate ceramics

Spin fluctuation and spin variation phenomena with comparative crystal field energy and Hund energy for Co doped barium strontium titanate.

Measurements of pyroelectric coefficients of BT and BST ceramics

In the work, the field and temperature dependencies on the pyroelectric coefficients of ceramic capacitor structures were measured. Barium titanate (BT) and solid solutions of barium-strontium titanate (BST) were investigate. At temperatures range from 20 °C to 30 °C, the values of the pyroelectric coefficients of the BST ceramics (p) 10-5 - 10-4 C/m2 K exceeded p for the BT ceramics by an order. The developed measurement technique made it possible to carry out direct pyroelectric coefficients measurements and determine the polarization initial state of the samples, regardless of their phase state.

Effect of defects on the band gap and photoluminescence emission of Bi and Li co-substituted barium strontium titanate ceramics

Since the discovery of an effective role for defects in improving the performance of ceramic materials in practical application, investigation of defects and their impact on the development of optical properties in condensed matter physics have received widespread attention. In this work we synthesized a lead free (Ba0·60Sr0.40)(1-x)(Bi,Li)xTiO3 (BST6:BLx%); (0%≤x ≤ 8%) ceramics using a conventional solid-state reaction method. X-ray diffraction patterns along with Rietveld refinement, Micro-Raman (MR) spectroscopy, X-ray Photoelectron Spectroscopy (XPS), UV–visible, Electron Spin Resonance (ESR) and photoluminescence (PL) measurements are utilized to characterize these ceramics. XRD, and Raman analysis have proven cubic phase symmetry with a contraction in bond length as the Bi and Li concentrations increased. XPS and ESR results confirm the presence of Ti3+ surface defects (TSD) and oxygen vacancies (VO) on the co-substituted samples sintered at high temperature. The optical results show a decrease in the bandgap energy from 3.14 eV to 2.76 eV and a wide-PL band emission on the green band, caused by recombination of the radiative free electrons and holes trapped around the surface oxygen vacancies. Defect levels created within the bandgap might act as recombination centres, and this can give the possibility of using BST6:BLx as a green light emission source in future practical applications.

Multiferroic properties of barium strontium titanate ceramics doped with gadolinium and iron

The dielectric and magnetic properties of ceramics based on barium titanate and solid solutions of barium strontium titanate doped with iron and gadolinium ions at concentrations below 5 mol.% have been investigated. It is shown that these ceramics exhibit paramagnetic behavior in a wide temperature range from 10 to 300 K and their dielectric and magnetic properties are strongly influenced by the doping.

Colossal dielectric permittivity and high energy storage efficiency in barium strontium titanate ceramics co-doped with bismuth and lithium

The development of energy storage devices in lead-free perovskite materials is critically important in addressing the environmental issues of perovskite lead. In this article, for the first time, lead-free (Ba0.60Sr0.40)(1−x)(Bi,Li) x TiO3, abbreviated as (BST6:BLx%); (0%⩽ x ⩽ 8%) ceramics, have been successively synthesized via the conventional solid-state reaction method. The structural evolution, dielectric and energy storage properties, as functions of co-doping levels, were systematically studied by x-ray diffraction, x-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy, scanning electron microscopy, impedance analyzer, and a Radiant Precision Premier II Analyzer. It was found that a small amount of co-dopants induced a colossal permittivity (CP) (over 105) with low loss (<0.1), a maximum energy storage density of 0.3856 J cm−3 with a BDS of ∼100 kV cm−1, and an efficiency of over 90%. The defects and chemical state of the elements contained in the material’s surface were investigated using XPS. In conjunction with the results of XPS and complex impedance studies, the mechanism of massive permittivity was interpreted based on a defect-dipole model. We believe that BST6:BLx% ceramics, as CP and high energy storage efficiency materials, might be considered a promising candidate for high energy storage applications.

Investigation on dielectric properties of Al2O3, ZnO and MgO doped Ba0.7Sr0.3TiO3 ceramics

Being an insulator material with high relative permittivity, Barium Strontium Titanate (BST) ceramics can be used extensively in many applications if its dissipation factor is reduced. In this paper, we investigate dielectric properties of Ba0.7Sr0.3TiO3 ceramics when doped with Al2O3, ZnO and MgO. At first, Ba0.7Sr0.3TiO3 ceramics was synthesized using conventional solid-state reaction technique. Further the Ba0.7Sr0.3TiO3 ceramic samples were doped with 0.5, 1.0, 2.0, 4.0 and 8.0 wt% Al2O3. Similarly Ba0.7Sr0.3TiO3 ceramic samples were doped with same weight percentages of ZnO and then MgO. After making pellets of all these samples, silver paste was coated for top and bottom electrodes to form ceramic based Metal-Insulator-Metal (MIM) capacitors. The dielectric properties were measured at room temperature using Hioki 3532-50 LCR Hi-Tester. It is noted that relative permittivity increases with dissipation factor (dielectric loss) irrespective of doping material and doping concentration. The dissipation factor achieved by 2.0 wt% ZnO doped Ba0.7Sr0.3TiO3 ceramics is 0.0087, which is promisingly very low. Further it is observed that 2.0 wt% ZnO doped Ba0.7Sr0.3TiO3 ceramics possesses highest figure of merit (relative permittivity to dissipation factor ratio) and hence optimum performance among the doping materials and doping concentrations considered.

The effect of Ba/Sr ratio on the Curie temperature for ferroelectric barium strontium titanate ceramics

The powders of lead-free material namely (nonhazardous) barium strontium titanate (BST) with different stoichiometric compositions have been synthesized by the sol–gel method. Ba[Formula: see text]Sr[Formula: see text]TiO3 (BST) materials possess the properties of both ferroelectric and dielectric materials. These materials have spontaneous polarization that can be reversed by an applied electric field and they remain polarized even when the applied external electric field is removed. Synthesized samples have been subjected to structural, morphological, and dielectric characterizations. In this study, BST nanopowders with different substitutions of [Formula: see text] (where [Formula: see text]= 0.2, 0.3, 0.4, 0.5, and 0.6) were prepared by the sol–gel method, which is an easy method with low power consumption and low temperature requirement and produces higher yield. Nanopowders had average particle sizes of 12–24 nm and particles sizes after sintering at 1000[Formula: see text]C for 3 h were 197, 267, 79.80, 63.09, and 63 nm. All resulting pellets had a polycrystalline structure. Crystal structure, space group, morphological characterization, and particle size were determined from the structural analysis using X-ray powder diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). The dielectric measurements were made for BST pellets under different frequencies (1–200 kHz) from room temperature to 250[Formula: see text]C. The dielectric constants for the bulk were 743, 1566, 1091, 766, and 626 for [Formula: see text]= 0.2, 0.3, 0.4, 0.5, and 0.6, respectively. From dielectric measurements, samples with [Formula: see text]= 0.2 and 0.3 had the Curie temperatures of 70[Formula: see text]C and 28.5[Formula: see text]C, respectively, and remained intact below 0[Formula: see text]C. The sample with [Formula: see text]= 0.3 had a good dielectric measurement and moderate dissipation factor; it may be used in capacitance application as energy stores.

Effects of mechanical activation on the formation and sintering kinetics of barium strontium titanate ceramics

The influence of mechanical activation on the formation, sintering kinetics and morphology was investigated in sintered barium strontium titanate (BST) ceramics with different Ba-to-Sr ratios. Initial powders were mechanically activated for 20 and 120 min, leading to mechano-chemical reaction and formation of BaxSr1-xTiO3 phases. Agglomeration was found to represent an important factor in the process of formation of BaxSr1-xTiO3 phases around 800?C and during sintering. It reduces the effectiveness of mechanical activation on formation of BaxSr1-xTiO3 phases beyond the short period (20 min), while in the process of sintering, prolonged mechanical activation (120 min) leads to a significant reduction in sintering temperature and the corresponding value of activation energy. In addition, all three systems show a phase transformation around 1100?C, attributed to the hexagonal-to-cubic phase transition. Morphology of the final sintered ceramics can be correlated primarily with the state of the pre-sintered powder, where mechanically activated powders with smaller particle size produced more compact and less porous final product.

Direct and indirect measurement of large electrocaloric effect in barium strontium titanate ceramics

AbstractBarium strontium titanate (Ba1‐xSrxTiO3‐BST) ceramics, where x = 0.05, 0.15, 0.25, and 0.35, was prepared via a solid‐state reaction method. The lattice structures and morphologies of the ceramic samples were analyzed using X‐ray diffraction and scanning electron microscopy technologies. The dielectric and ferroelectric properties of the BST ceramics were characterized using a precision impedance analyzer and a ferroelectric polarization‐electric field (P‐E) hysteresis loop tester, respectively. The electrocaloric effect was indirectly calculated using the Maxwell relations and P‐E loops as a function of temperature and electrical field, and also directly measured using a computer‐controlled thermocouple and high‐voltage power supply. An adiabatic temperature change of 1.82 K was procured, indicating a promising potential in the applications as cooling devices.

Glass modified barium strontium titanate ceramics for energy storage capacitor at elevated temperatures

A glass with composition of B2O3-Bi2O3-SiO2-CaO-BaO-Al2O3-ZrO2 (BBSZ) modified BaxSr1-xTiO3 (BST, x = 0.3 and 0.4) ceramics were prepared by a conventional solid state reaction method abided by a formula of BST + y%BBSZ (y = 0, 2, 4, 7, and 10, in mass). The effect of BBSZ glass content on the structure, dielectric properties and energy storage characteristics of the ceramics was investigated. The dielectric constant reduced but the endurable electrical strength enhanced due to the BBSZ glass addition in BST ceramics. In particular, the dielectric loss of the ceramics at elevated temperature (e.g. 200 °C) can be strongly suppressed from tanδ>20% to tanδ<3% after BBSZ glass modification. For Ba0.3Sr0.7TiO3+2% BBSZ ceramics, an optimized energy storage density (γ = 0.63 J/cm3) and efficiency (η = 91.6%) under an applied electric field of 160 kV/cm was obtained at room temperature. Meanwhile, the temperature dependent polarization-electric field (P-E) hysteresis loops were measured to evaluate the energy storage characteristics of the ceramics potential for high voltage capacitor application at elevated temperatures.

Synthesis of Ba0.7Sr0.3TiO3 ceramics via hybrid method

Barium strontium titanate (BST) ceramics were prepared by the hybrid method between Solid-state reaction and Sol-gel combustion methods using urea as a fuel. The crystalline powders were prepared by the mixed precursors between Solid-state reaction: Solgel combustion with the molar ratio of 1:0.3 and calcined at 950°C for 2 hours. The BST ceramics were fabricated from calcined powders by sintering at 1050-1350°C and instigated the crystal structures by XRD. All sintering samples have a pure perovskite structure corresponding to JCPDS no. 34-0411. The SEM revealed an increasing of a gain size when with increasing sintering temperature. The highest dielectric constant 11580 was found in the sample prepared at 1350°C for 4 hours with dielectric loss of 0.007.

Structural and dielectric properties of sol–gel derived Ba1–xSrxTiO3 (0 ≤ x ≤ 0.5) ceramics for energy storage applications

Barium strontium titanate (Ba1–xSrxTiO3, BSTO: x = 0, 0.3 and 0.5) ceramics were prepared by sintering sol–gel derived BSTO powders at 1350 °C for 2 h. Average grain size of BSTO ceramics decreased from 15 to 2 μm with increasing Sr molar fraction. X-ray structural analysis revealed that BSTO ceramics exhibited tetragonal structure (x = 0 and 0.3) and transformed into cubic structure at high Sr molar fraction (x = 0.5) at room temperature. Dielectric constant of the BSTO ceramics was measured between −60 and 180 °C and frequency range of 1–100 kHz. Temperature transition from ferroelectric to paraelectric phase (Curie temperature: TC) decreased linearly from 125 to −30 °C as Sr molar fraction increased. The dielectric constant exhibited frequency-independent behavior in the frequency range investigated. A diffuse dielectric constant peak was evident for BSTO with Sr molar fraction of 0.5 due to the effect of fine-grained size. Polarization–electric field (P–E) at room temperature presented a well-defined hysteresis loop for BSTO (x = 0 and 0.3), indicating their ferroelectric characteristics. At a high Sr molar fraction of 0.5, the P–E loop became a linear relation, indicating a paraelectric phase. Energy storage density of BSTO with x = 0 was about 0.2 J/cm3; however, energy storage efficiency was less than 50%. After doping with Sr molar fraction of 0.5, energy storage density decreased to 0.1 J/cm3 but its energy storage efficiency significantly improved to 90%.

Influence of A-site deficiency on electrical characteristics of barium strontium titanate perovskite dielectrics

Improvement of dielectric properties and insulation resistance are important for the development of high-performance dielectric materials. Various techniques can be used in order to improve the performance of such materials. The effect of A-cation deficiency on the electrical properties of barium strontium titanate ceramics is an interesting topic of investigation. Thus, this study examined the stoichiometric, 0.01 mol Ba-deficient, and 0.01 mol Sr-deficient compositions of (Ba0.8Sr0.2)TiO3 ceramics. Changes in the dielectric characteristics were observed in the 0.01 mol Ba-deficient and 0.01 mol Sr-deficient compositions. The characteristics of electrical conduction revealed by impedance analysis are different at high temperatures when Ba-deficiency and Sr-deficiency are introduced to the dielectrics. The Ti4+ state for the Ba-deficient composition is maintained. However, the Ti4+ state partially changes to the Ti3+ state, giving rise to the polaron hopping conduction process for Sr-deficient composition. Therefore, this study shows that a minor deviation of the A-cation from stoichiometry can induce a different conduction process while maintaining the dielectric permittivity characteristics.