Barium Strontium Titanate Ceramics Research Articles

Properties of Barium Strontium Titanate (Ba1-xSrxTiO3, 0 £ x £ 1) Ceramics Prepared by Hydrothermal Process

Properties of Barium Strontium Titanate (Ba1-xSrxTiO3, 0 £ x £ 1) Ceramics Prepared by Hydrothermal Process

Effect of Ferroelectric Domain on Fatigue Fracture Behavior in Piezoelectric Ceramics

Fatigue tests on lead zirconate titanate (PZT) were performed by using single-edge-V-notched specimens under cyclic mechanical loading with or without superposition of a DC electric field. Fatigue life was prolonged by applying a DC electric field to the PZT ceramics. To estimate the domain contribution, fatigue tests on barium strontium titanate (BST) ceramics in both ferroelectric and paraelectric phase were carried out. The fatigue life of the ferroelectric phase was much shorter than that of the paraelectric phase. Comparing the fatigue lives of two PZT ceramics with different values of coercive electric field (Ec) revealed that the fatigue life of the PZT with higher Ec is about one order of magnitude longer than that with lower Ec when the stress-intensity factor of fatigue test is low. It is therefore concluded that non-180°domain switching probably deteriorates the fatigue life of ferroelectric ceramics.

Pyroelectric response mechanism of barium strontium titanate ceramics in dielectric bolometer mode: The underlying essence of the enhancing effect of direct current bias field

Pyroelectric response mechanism of Ba0.70Sr0.30TiO3 ceramics under dielectric bolometer (DB) mode was investigated by dielectric and pyroelectric properties measurement. The variations of total, intrinsic, and induced pyroelectric coefficients (ptot, pint, pind) with temperatures and bias fields were analyzed. pint plays the dominant role to ptot through most of the temperature range and pind will be slightly higher than pint above T0. The essence of the enhancing effect of DC bias field on pyroelectric coefficient can be attributed to the high value of pint. This mechanism is useful for the pyroelectric materials (DB mode) applications.

Sintering and Dielectric Properties of Sr-Rich Barium Strontium Titanate (BST) Ceramics Fabricated by a Mixed-Phase Method

Ba 1-x SrxTiO3(x=0.6 to 0.9 interval of 0.1) ceramics were developed by a BT sol-assisted sintering technology with a mixed-phase sintering from the mixture of BT and ST powders synthetized by a solid-state reaction method. The sintering behavior and dielectric properties of the ceramics were investigated. Results show that the sintering activity of the ceramics becomes worse and worse when increased the strontium content, and the sintering condition have a remarkable effect on the density of the ceramics. Dense ceramics were obtained when sintered at 1280°C for 8h with a relatively density of above 94%. The composition had a strong effect on the dielectric properties, while the sintering schedule had a little influence on the dielectric temperature spectrum of the BST ceramics. The Ba 1-x SrxTiO3(x=0.9) ceramic with dielectric constant～335, loss tangent～0.000625 at 1.85 GHz and 20°C, and good temperature stability of dielectric constant above the room temperature is attained.

The High DC Electric Field Effects on the Dielectric Behavior of Barium Strontium Titanate Ceramics

BaxSr1-xTiO3 (x=0.4, 0.5, 0.6) ceramics were fabricated by the conventional solid-state reactions method. The temperature dependences of the dielectric constant and tunability were investigated under high DC electric field. It was found that the change of dielectric constant and tunability under the applied electric field were closely related to ferroelectric phase, phase transition region and paraelectric phase states. The Curie temperature (Tc) was gradually shifted to higher temperature and were broadened and depressed with increasing of DC electric field. The tunability dependence of temperature exhibits different trends in a wide temperature range and reaches a maximum value near the ferroelectric-paraelectric phase transition. These results may be helpful in understanding the mechanism of dielectric response under higher electric field.

Dielectric properties of Bi-doped Ba0.8Sr0.2TiO3 ceramic solid solutions

Bismuth-doped barium–strontium–titanate ceramics of the formula (Ba 0.8 Sr 0.2 ) (1−1.5 y ) Bi y TiO 3 were prepared using a conventional solid-state reaction method. The structure, dielectric properties, and ferroelectric relaxor behaviour of all compositions were thoroughly investigated. The findings revealed a broad dielectric anomaly and a shift in dielectric maxima towards higher temperatures with increasing frequency. The diffuseness degree indicator γ was about 1.68, and dielectric relaxation was noted to follow the Vogel–Fulcher relationship, with T f =185 K, f 0 =1.18×10 10 Hz, and E a=0.35 eV, which further supported the spin-glass-like properties of BBSTs. The latter were also noted to display significant ferroelectric relaxor behaviour that could be attributed to the presence of Bi 3+ doping ions. The degree of relaxation behaviour was noted to increase with the increase in bismuth concentration. Raman spectra were investigated as a function of temperature, and the findings confirmed the results from X-ray and dielectric measurements. Among the compositions assayed in this solid solution, 10% Bi-doped Ba 0.8 Sr 0.2 TiO 3 yielded promising relaxor properties that make it a strong candidate for future industrial application in the production of efficient and eco-friendly relaxor ferroelectric materials.

Investigation of ferroelectric phase transition for barium strontium titanate ceramics by in situ Raman scattering

The origin of the change in ferroelectric properties of Ba0.6Sr0.4TiO3 (BST60) ceramics near Curie temperature due to the application of an electric field was investigated by using Raman scattering spectroscopy. The results showed that different structural responses were induced upon electric fields (E). The relative intensity ratio between the vibrating modes of A1(TO3) and E(TO4) was attributed to the structural phase transitions induced by the electric field E. The increase in degree of structural distortion with increasing E was in a good agreement with the gradual shift in Curie point to higher temperature. These electric-field-induced structural effects contributed significantly to the tunability of the BST60 ceramics. These conclusion should be also applicable to other ferroelectric materials.

Dielectric properties and phase transitions of La2O3- and Sb2O3-doped barium strontium titanate ceramics

The dielectric properties and phase transition characteristics of La2O3- and Sb2O3-doped barium strontium titanate ceramics prepared by solid state route were investigated. The microstructure was identified by X-ray diffraction method and scanning electron microscope was also employed to observe the surface morphologies. It is found that (La, Sb)-codoped barium strontium titanate ceramics exhibit typical perovskite structure and the average grain size decreases dramatically with increasing the content of Sb2O3. Both La3+ ions and Sb3+ ions occupy the A-sites in perovskite lattice. The dielectric constant and dielectric loss of barium strontium titanate based ceramics are obviously influenced by La2O3 as well as Sb2O3 addition content. The tetragonal-cubic phase transition of La2O3 modified barium strontium titanate ceramics is of second order and the Curie temperature shifts to lower value with increasing the La2O3 doping content. The phase transition of (La, Sb)-codoped barium strontium titanate ceramics diffuses and the deviation from Curie-Weiss law becomes more obvious with the increase in Sb2O3 concentration. The temperature corresponding to the dielectric constant maximum of (La, Sb)-codoped barium strontium titanate ceramics decreases with increasing the Sb2O3 content, which is attributed to the replacement of host ions by the Sb3+ ions.

Synthesis and characterization of nickel oxide doped barium strontium titanate ceramics

Barium strontium titanate (BST) ceramics (Ba0.6Sr0.4)TiO3 were synthesized by solid state sintering using barium carbonate, strontium carbonate and rutile as the precursor materials. The samples were doped with nickel oxide in different proportions. Different phases present in the sintered samples were determined from X-ray diffraction investigation and the distribution of different phases in the microstructure was assessed from scanning electron microscopy study. It was observed that the dielectric properties of BST were modified significantly with nickel oxide doping. These ceramics held promise for applications in tuned circuits.

Dielectric properties of Barium Strontium Titanate (BST) ceramics synthesized by using mixed-phase powders calcined at varied temperatures

Compositionally inhomogeneous Barium Strontium Titanate (BST) ceramics with greatly improved dielectric temperature stability was developed by the combination of the solid-state reaction and mixed-phase method with the help of a sol-assisted sintering technology. It is found that the powders' calcination temperatures have significant effects on the microstructure and the dielectric temperature stability of the sintered BST ceramics. Increasing calcination temperature of either powder slightly degrades the BST ceramics' sintering properties, but can significantly suppress and broaden their Curie peaks. Comparatively, increasing the ST powders' calcination temperature has more obvious effectiveness. When BT and ST powders are calcined at 1100°C and 1200°C, respectively, the sample sintered at 1280°C for 2h has excellent dielectric temperature stability, uniform grain size and relatively dense microstructure (93% R.D).

The influence of mechanical activation on sintering process of BaCO3-SrCO3-TiO2 system

In this article the influence of mechanical activation on sintering process of bariumstrontium-titanate ceramics has been investigated. Both non-activated and mixtures treated in a planetary ball mill for 5, 10, 20, 40, 80 and 120 minutes were sintered at 1100-1400?C for 2 hours in presence of air atmosphere. The influence of mechanical activation on phase composition and crystal structure has been analyzed by XRD, while the effect of activation and sintering process on microstructure was investigated by scanning electron microscopy. It has been established that temperature of 1100?C was too low to induce final sintering stage for this system. Electrical measurements have been conducted for the densest ceramics sintered at 1400?C for 2 hours.

Structural and mechanical properties characterization of barium strontium titanate (BST) ceramics

Ba(1-x)Sr(x)TiO3 ceramics, where x = 0.05, 0.10, 0.15, and 0.20, were prepared by solid state reaction technique. X-ray diffraction analysis confirmed the formation of single phase perovskite structures. Mechanical properties such as ultrasonic attenuation, longitudinal wave velocity, and longitudinal elastic modulus were studied by an ultrasonic pulse echo technique at 2 MHz. Investigations of ceramic microstructures and mechanical properties showed its dependence on composition and sintering time. Increasing of Sr content, x, resulted in a decrease in bulk density and ultrasonic attenuation and an increase in velocity and modulus. Also, size of crystallites and c/a ratio were found to decrease with increasing of x, and increased with increasing of sintering time. High temperature ultrasonic studies showed, in addition to Curie phase transition, two relaxation peaks and its origin was investigated. The acquired structural and mechanical results were correlated and discussed.

Polarization characteristics of graded thick Ba1 − x Sr x TiO3 films

The barium strontium titanate ceramics Ba1 − xSrxTiO3 with a spatially variable composition has been prepared according to the thick film technology (tape casting). The strontium content over the film thickness is varied from 0 to 30 mol %. The structure and polarization characteristics of the samples prepared have been investigated. It has been found that the polarization characteristics of multilayer structures are determined by the ratio between the thicknesses of layers with different compositions and by their properties. No shift of the hysteresis loops in the graded thick Ba1 − xSrxTiO3 (x = 0–0.3) films has been revealed. The results obtained have been analyzed in the framework of modern theoretical approaches.

A Novel Electron Paramagnetic Resonance Phenomenon in a Barium Stronium Titanate Ceramic

The electron paramagnetic resonance (EPR) technique was employed to investigate the point defects in barium strontium titanate ceramics. All samples showed a strong EPR signal with g = 2.000, which was indexed as intrinsic Ti-vacancy defects. In (Ba0.85Sr0.15)TiO3ceramic, which showed a tetragonal symmetry and consisted of the crystallites with average size of ~ 220 nm, a novel EPR powder spectrum was observed - the g-factor of theg= 2.000 signal evolved into ag-tensor, and the two weak signals withg3= ~ 2.6 andg1= ~ 1.6 gradually shifted toward the g2 = 2.000 signal and approached to each other with increasing temperature.

Dielectric and tunable properties of barium strontium titanate ceramics under the stresses

The external stress dependence of dielectric and tunable properties of Ba x Sr 1− x TiO 3 ( x = 0.65) ceramics has been investigated. The results reveal that the Curie peaks of samples are suppressed and broadened, the Curie temperature ( T c) is slightly shifted to lower temperature with an increase of external stress. Correspondingly, the tunability decreases from 66.6% to 58.8% in the vicinity of cubic–tetragonal (C–T) phase transition at an applied DC electric field of 10 kV/cm. These results could be useful for the design of devices and practical applications of Ba x Sr 1− x TiO 3 ceramics.

Transparent Barium Strontium Titanate Ceramics Prepared by Spark Plasma Sintering

Transparent ferroelectric ceramics are valuable for many applications in electro-optical devices. In this paper, transparent barium strontium titanate (BST) ceramics were prepared by spark plasma sintering and thermal treatment. The microstructures and optical properties of the transparent BST samples were investigated. The densities of the BST samples were nearly theoretical and the samples were optically transparent. Both the transmittances at 633 nm of the Ba0.3Sr0.7TiO3 and Ba0.4Sr0.6TiO3 ceramics with a thickness of 0.3 mm are over 74%. The lead-free optical transparent ferroelectric BST ceramics are promising candidates for electro-optical applications.

Effects of Magnesium Doping on Phase Transitions and Dielectric Figure of Merit of Barium Strontium Titanate Ceramics

Ba0.6Sr0.4(Ti1−xMgx)O3 (BSTM) ceramics were prepared by using a solid‐state reaction process. X‐ray diffraction results indicated that the solubility limit of Mg in Ba0.6Sr0.4TiO3 was about 3 mol%. Doping of Mg into BST led to diffused cubic–tetragonal (C–T) phase transition and reduced Curie temperature. The diffused parameter γ obtained by fitting the modified Curie–Weiss laws increased with increasing Mg content. Dielectric properties of the BSTM ceramics were measured. Figure of merit of BSTM3 was up to 127.8 at 17.5 kV/cm. Its dielectric loss was as low as 0.00133 at 1 kHz and room temperature.

Compositionally graded ceramics based on Ba1 − x Sr x TiO3 solid solutions

Homogeneous and compositionally graded barium strontium titanate (Ba1 − xSrxTiO3) ceramics have been prepared in the form of thick films by slip casting. The strontium content was varied across the graded films from 0 to 30 mol %. Microstructural examination and dielectric measurements have shown that, varying the composition and thickness of the layers in graded structures and the sintering conditions, one can control the behavior of their dielectric characteristics and obtain a small temperature coefficient of capacitance in a predetermined temperature range.

Microwave Property of Low-Temperature-Sintered Ba1−xSrxTiO3 Ceramics with B-Li Glass Sintering Aid

This paper reports on fabrication and characterization of low-temperature-sintered barium-strontium titanate (BST) ceramics with B-Li glass as sintering aid. With the addition of B-Li glass, the sintering temperature of BST can be effectively reduced from 1350 to 920°C due to the presence of a liquid phase. The effects of B-Li glass addition on phase composition, microstructure, dielectric properties, and microwave properties of the BST ceramics were sytematically investigated. The sample (Ba0.50Sr0.50TiO3) with 5.0 wt% B-Li sintered at 920°C for 5 h exhibits optimized room temperature dielectric properties, including a moderate dielectric constant (ϵ = 1051), a low dielectric loss (0.0048) and a high tunability (31%) at dc electric field of 45 kV/cm and 10 kHz. At 1.150 GHz, it possesses a dielectric constant of 695 and Q value of 207.

Thickness-induced resonance-based complex permittivity measurement technique for barium strontium titanate ceramics at microwave frequency

Thickness-induced resonance would be the major factor of uncertainty for complex permittivity measurement by using transmission/reflection method when the thickness of sample is several integer multiples of the half wavelength. A new technique for complex permittivity measurement was presented in this paper using the thickness-induced resonance for barium strontium titanate (BST) ceramics at microwave frequency. Simulated and experimental results show that there are some resonance peaks on the transmittance versus frequency curve and the complex permittivity can be calculated from the resonance.