Barium Stannate Titanate Ceramics Research Articles

Size effect on piezoelectric properties of barium stannate titanate ceramics prepared from nanoparticles

Piezoelectric properties of Ba(Ti1−xSnx)O3 ceramics with x = 0.025, 0.045 and 0.065, prepared from 16 nm powders, were compared with those of the corresponding ceramics obtained from 86 nm powders to see the effect of tin content and particle size of the starting powders. Ba(Ti1−xSnx)O3 powders were synthesized by solid state reaction of BaCO3, TiO2 and SnO2 at 1,050 °C. The powders were high energy ball milled to produce nanocrystalline powders having average particle size of 16 nm. The milled powders were sintered at 1,350 °C for 4 h to yield ceramics. For these ceramics, increasing Sn content from x = 0.025–0.065 produces a decrease in (1) unipolar strain level s from 0.084 to 0.027 %, and (2) electromechanical coupling factor kp from 33.6 to 19.3 %. However, the bulk density, room temperature dielectric constant and piezoelectric charge constant d33 exhibit an increase from 5.03–5.84 g/cm3, 1,342–2,156 and 7–110 pC/N, respectively, with increasing Sn content. The increasing trend of density and d33 presently observed is in sharp contrast to the result of corresponding ceramics prepared from 86 nm nanopowders. The present study reveals a cooperative mechanism involving both the nanoscale size of the starting particles and optimum tin content which results in the enhancement of d33 with tin content.

Effect of gamma ray irradiation on the ferroelectric and piezoelectric properties of barium stannate titanate ceramics

Tin doped barium titanate ceramics has been obtained by solid state reaction method followed by high energy ball milling. The effect of heavy dose gamma ray irradiation on the ferroelectric and piezoelectric properties of the synthesized barium stannate titanate ceramics has been observed. It has been found that on irradiation the ferroelectric property decreases with decreasing values of Pr and Ec. The piezoelectric properties including d33, electrostrictive strain and electromechanical coupling coefficient (Kp) also decrease following the same trend of Pr and Ec. Grain size decreases and grain patterns become irregular after irradiation as observed from SEM micrographs. The Thermoluminescence (TL) property of the barium stannate titanate ceramics has also been investigated and reported.

Microstructure, dielectric properties and diffuse phase transition of barium stannate titanate ceramics

BaSnxTi1–xO3 (short for BTS) ceramics are prepared via the conventional solid state reaction method. The microstructures, diffuse phase transiton, dielectric and ferroelectric properties of BTS ceramics were investigated. These results indicate that Sn4+ ions have entered the unit cell maintaining the perovskite structure of solid solution. The incorporation of SnO2 can limit grain growth in the BTS ceramics. The Curie temperature of BTS ceramics decreases with the increasing of tin content. Addition of tin can decrease dielectric loss of BTS ceramics at room temperature. The diffuseness of the phase transition of BTS ceramics enhances with the increasing of tin content. The coercive electric field (EC) increases as tin content increases when x is 0.10–0.20. Moreover, the remanent polarization (Pr) of BTS ceramics decreases with the increasing of tin content.

Structural and electrical characteristics of dysprosium-doped barium stannate titanate ceramics

Effects of dysprosium (Dy) amphoteric doping on the structural, dielectric and electric properties of barium stannate titanate (BTS) ceramics have been studied. X-ray diffraction analyses reveal that all Dy-doped BTS ceramics exhibit cubic perovskite structure until to 1 mol%. Dy doping at the A site shows lower solubility than that at the B site. SEM surface morphologies display that the Dy B site doping is beneficial for the compact and homogeneous grain distribution. The dielectric constant and loss tangent are reduced with increase of the doping levels. Impedance spectroscopy investigation demonstrates that all samples are insulating at room temperature. Doping alters the full resistive regions of pure BTS ceramics to Doped BTS with insulating grain boundaries and semiconducting bulk regions, but the doping contents has little effect on changing the electric structures.

Properties of Barium Stannate Titanate with Boron Oxide Addition

In this study, barium stannate titanate ceramics with an addition of boron oxide were synthesized via a solid-state sintering method. The effect of sintering aid on electrical and mechanical properties of barium stannate titanate ceramics was investigated. It was found that, the ceramic with 2 wt% boron oxide showed the lowest porosity and the highest dielectric constant of ~ 13700 at room temperature. In addition, an increase in the boron oxide content was observed to enhance the hardness of the ceramics. These results may be helpful in the multilayer capacitor applications.

Time domain response and the data analysis of ferroelectric discharge current

The time domain method is more reliable for the study of nonlinear dielectric response compared with frequency domain analysis. A Tikhonov regularization method, which is widely adopted for ill-posed problem, is described for derivation of the relaxation time distribution function, g(τ), from the ferroelectric discharge current in time domain. The new method allows study of the structure variation and the relaxation behavior of ferroelectrics at different temperatures. For barium stannate titanate ceramics (BTS20), g(τ) has been successfully derived; the relaxation peaks move to shorter times with increasing temperature in the range 20–60°C, which may indicate a space charge thermal activation process. However, g(τ) could not be derived from the discharge current by the regularization method for BTS20 at temperatures above 60°C or for lanthanum-doped lead zirconium titanate transparent ceramic (PLZT), since the data do not satisfy the discrete Picard condition, which is a valid criterion for regularization method.

Dielectric and Piezoelectric Properties of B<sub>2</sub>O<sub>3</sub> and SnO<sub>2</sub> Doped Barium Titanate Ceramics

Boron oxide doped barium stannate titanate ceramics were prepared by a solid-state reaction method. Properties of the ceramics were investigated. The experimental results showed that most properties of the ceramics depend on the sintering temperature. The higher relative permittivity of 13887 with tan 0.034 at 34 °C was observed for the samples sintered at 1350 C. Piezoelectric coefficient (d33) of the samples was found to be in the range of 90 - 115 pC/N. However, the optimum d33 coefficient was observed for the sample sintered at 1250 C.

The Preparation of Barium Stannate Titanate Ceramics via Solid State Reaction Method

In this work, the optimum conditions for the preparation of barium stannate titanate (Ba(Sn0.05Ti0.95)O3 ; BST5) ceramics by solid state reaction method were investigated. The samples were heated at calcination temperatures from 600 to 1200 oC for 4 h and sintering temperatures from 1250 to 1400 oC for 2 h. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were used to evaluate the optimum conditions for calcination. The phase formation was carried out by X-ray diffractometer (XRD). The microstructure was studied by using a scanning electron microscope (SEM). It was found that, a high purity of perovskite powders were obtained with a calcinations temperature at 1200 oC. The percent of the perovskite phase and lattice parameter a were increased by increasing the calcination temperatures. The average particle size was increased from 0.6 to 1.0 µm when increasing the calcination temperatures from 600 to 1200 oC. A pure cubic perovskite phase was found in all the sintered samples. The average grain size is in the range of 1.2 to 43.3 µm when increasing of sintering temperatures from 1250 to 1400 oC. The maximum of density and dielectric constant was observed in a 1400 oC sintered pellet.

Preparation, structure and dielectric property of barium stannate titanate ceramics

The processing route of barium stannate titanate ceramics were optimized to prepare full composition range solid solution sample. The phase structure, microscopic morphology and dielectric properties of barium stannate titanate ceramics were studied. X-ray diffraction patterns indicated that the samples are of single perovskite structure. Linear empirical relationship between crystal lattice and tin content was proposed. This relationship is valid covering the full composition range, which suggests that this solid solution system is ultimate mutual soluble. The phase transition behavior was studied and a phase diagram was obtained based on the dielectric measurements.

Isothermal relaxation of field-biased barium stannate titanate

The isothermal time dependences of the dielectric constant and the discharging current of barium stannate titanate ceramics after application or removal of a step field were investigated in both ferroelectric and paraelectric temperature regions. The experimental results exhibited a substantial difference for these two phases. For the ferroelectric phase, the relaxation of the dielectric constant is weak and the discharging current obeys Hammon’s model. While for the paraelectric phase, the relaxation is relatively strong and the discharging current obeys the complex exponential decay model. The relaxation of the field-induced piezoelectric resonance indicated the first relaxation observed in a paraelectric phase sample corresponding to homocharges. The authors proposed that the transportation of homocharges is the microscopic origin of the strong relaxation observed in the paraelectric phase.

Abnormal C– V curve and clockwise hysteresis loop in ferroelectric barium stannate titanate ceramics

Reversible hysteresis loop, defined as integral of small signal dielectric constant with electrical field, represents the contribution of the reversible part of polarization. In barium stannate titanate ceramics, field dependence of small signal dielectric constant was abnormal. The subsequent mathematical integral showed an abnormal clockwise hysteresis loop in the temperature range of 10–40 °C. The ferroelectric hysteresis loop measured by Sawyer–Tower circuit showed slim-waist or pinched shape. This phenomenon may reveal abnormal domain switching mechanism and is believed to be related with the strong interaction between point defects and domain walls.

Tunability and relaxor properties of ferroelectric barium stannate titanate ceramics

Barium stannate titanate [Ba(SnxTi1−x)O3, x=0.1, 0.2, 0.3, and 0.4] ceramics were prepared using a conventional solid-state reaction process. Their dielectric properties were measured under direct current bias fields ranging from 0to2.5kV∕cm. A transformation from normal to relaxor ferroelectrics was observed when x⩾0.3. Broken long-range order or “dirty” ferroelectric domains and nanodomains were observed in Ba(Sn0.1Ti0.9)O3 and Ba(Sn0.4Ti0.6)O3 by transmission electron microscopy, respectively. Voltage driven tunability was found to decrease with increasing Sn content. The change from normal ferroelectric into relaxor ferroelectric had a negative impact on the tunability value of the materials.

Slow relaxation of field-induced piezoelectric resonance in paraelectric barium stannate titanate

A kind of slow relaxation of field-induced piezoelectric resonance is observed in paraelectric barium stannate titanate ceramics. The piezoelectric resonance peaks vanish in several minutes when bias field is either applied or removed. These phenomena may be universal for dielectrics and can be explained by a model of slow dipoles composed of injected homocharges. With this model, the authors predict a negative piezoelectric modulus of d33 when just the bias field is removed, and verify it by experimental results.

Evolvement of dielectric relaxation of barium stannate titanate ceramics

In barium stannate titanate (BTS) ceramics, low frequency dielectric relaxation was observed at temperatures far below room temperature. Curve fitting of the temperature dependence of dielectric constant was done according to empirical equations. Several models were employed to study the thermal activated relaxation. The inflexions of frequency difference of dielectric permittivity were compared with the phase transition region for the various compositions of barium stannate titanate ceramics.

Dielectric properties of barium stannate titanate ceramics under bias field

The biased dielectric properties of several barium stannate titanate ceramics were reported in the present study. The reversible dielectric nonlinearities (RDNs) were investigated both in ferroelectric and paraelectric phases. The increased lateral dielectric constant was illustrated with the anisotropy model in ferroelectric phase. The field dependence of dielectric constant was analysed by thermodynamic models in paraelectric phase.

Dielectric Characteristics and Tunability of Barium Stannate Titanate Ceramics

Ba(Ti1 −x Sn x )O3 solid solutions were prepared by a solid state reaction method, and their dielectric and tunable characteristics were investigated together with the microstructures and diffused phase transition behaviors. The dielectric relaxation behaviors were observed and became stronger with increasing x.The obvious field dependence of the present system was observed with high dielectric constant and low loss at relatively lower DC electric field. The excellent tunable dielectric characteristics were achieved for x= 0.15 at room temperature: tunability ∼ 56%, tan δ∼ 0.003 at 10 kHz under 7.6 kV/cm, indicating that it is a promising candidate for electric-field tunable dielectrics working at room temperature.