BCT Ceramics Research Articles

Composition-driven phase coexistence and functional properties of the (1-x)BZT-(x)BCT ceramics near the phase convergence region

The concept of composition-induced phase transformation in Lead Zirconate Titanate (PZT) at the Morphotropic Phase Boundary (MPB) has been employed to improve functional properties of the (1-x)BZT-(x)BCT ceramic. However, it was observed that the phase diagram of the (1-x)BZT-(x)BCT ceramic is different to the PZT. As a result, the nature of the superior functional properties found in (1-x)BZT-(x)BCT ceramic is unlike PZT and still unclear so far. In this work, functional properties; dielectric, ferroelectric, energy storage, and piezoelectric properties, of the (1-x)BZT-(x)BCT ceramics where x = 0.3 mol% to 0.6 mol% were evaluated at room temperature in comparison to the identification of phase coexistence using synchrotron x-ray powder diffraction (SXPD). This work found that changes of BCT content had a strong impact on the observed coexisting phases and functional properties. Moreover, the composition that showed the highest piezoelectric properties did not present the largest of saturation polarization. This implies that the functional properties of the (1-x)BZT-(x)BCT ceramics are not dependent on the presence of polarizations under the application of electric field. The contribution of non-180° domain switching also plays a vital role, especially in the piezoelectric properties. These findings would help to extend our knowledge of the nature of the (1-x)BZT-(x)BCT ceramic.

Improved dielectric and ferroelectric properties near Morphotropic phase boundary in Sm3+ modified BZT-BCT ceramics

Lead free polycrystalline (1-x)BZT-xBSCT ceramics with x = 0.45, 0.50 and 0.55 were prepared by solid state reaction method. The samples were sintered at 1325 °C. XRD analysis confirms the perovskite structure in all the samples. The average grain size of ceramics decreases from 7.38 to 5.36 μm with the increase in the BSCT content. A maximum value of ε equal to 5715 at room temperature was found for sample with x = 0.50 and all the samples show diffused phase transition. PE loops were recorded at different temperatures to understand the ferroelectric nature. The polarization extension mechanism was found in sample with x = 0.50 through Arrott curves. The results show that the properties in solid solution of Sm3+ modified BCT ceramics with BZT, which makes the prepared ceramics as the potential candidates for several applications.

Correlation of dielectric, ferroelectric, and magnetic properties with structural changes in Cr doped BCT ceramics

Correlation of dielectric, ferroelectric, and magnetic properties with structural changes in Cr doped BCT ceramics

Correction to: X-ray peak broadening analysis and dielectric studies of BCT ceramics; comparison of sol–gel and solid solution methods

Correction to: X-ray peak broadening analysis and dielectric studies of BCT ceramics; comparison of sol–gel and solid solution methods

X-ray peak broadening analysis and dielectric studies of BCT ceramics; comparison of sol–gel and solid solution methods

X-ray peak broadening analysis and dielectric studies of BCT ceramics; comparison of sol–gel and solid solution methods

Thermo-mechanical energy harvesting and storage analysis in 0.6BZT-0.4BCT ceramics

Present work shows waste energy (thermal/mechanical) harvesting and storage capacity in bulk lead-free ferroelectric 0.6Ba(Zr0.2Ti0.8)O3–0.4(Ba0.7Ca0.3)TiO3 (0.6BZT-0.4BCT) ceramics. The thermal energy harvesting is obtained by employing the Olsen cycle under different stress biasing, whereas mechanical energy harvesting calculated using the thermo-mechanical cycle at various temperature biasing. To estimate the energy harvesting polarization-electric field loops were measured as a function of stress and temperatures. The maximum thermal energy harvesting is obtained equal to 158 kJ/m3 when the Olsen cycle operated as 25–81 °C (at contact stress of 5 MPa) and 0.25–2 kV/mm. On the other hand, maximum mechanical energy harvesting is calculated as 158 kJ/m3 when the cycle operated as 5–160 MPa (at a constant temperature of 25 °C) and 0.25–2 kV/mm. It is found that the stress and temperature biasing are not beneficial for thermal and mechanical energy harvesting. Further, a hybrid cycle, where both stress and temperature are varied, is also studied to obtain enhanced energy harvesting. The improved energy conversion potential is equal to 221 kJ/m3 when the cycle operated as 25–81 °C, 5–160 MPa and 0.25–2 kV/mm. The energy storage density varies from 43 to 66 kJ/m3 (increase in temperature: 25–81 °C) and 43–80 kJ/m3 (increase in stress: 5–160 MPa). Also, the pre-stress can be easily implemented on the materials, which improves energy storage density almost 100% by stress induced domain switching. The results show that stress confinement can be used to enhance energy storage effectively.

Ferroelectric domain evolution in a Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 piezoceramic studied using piezoresponse force microscopy

Lead-free Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-0.5BCT) ceramics have drawn attention in recent years because of their outstanding dielectric and electromechanical properties, such as a piezoelectric coefficient d33 ∼ 620 pC N−1 and a large signal of d33* ∼ 1100 pm V−1 at 0.5 kV mm−1 at room temperature (RT). These particular properties are relevant to a range of applications. However, the structural origin of this high piezoelectric coefficient is still a subject of discussion. An in-depth understanding of the ferroelectric domain evolution of BZT-0.5BCT ceramics is crucial for probing the underlying mechanisms and for guiding practical applications. Using piezoresponse force microscopy (PFM), we have directly visualized the evolution of the BZT-0.5BCT domain structure using temperature and electric field stimulation on micrometer and nanometer scales. The PFM results unambiguously evidence the coexistence of wedge-shaped and lamellar domains with miniaturized nanodomain structures at RT. The temperature- and electric-field-dependent PFM study presented here highlights the critical role of wedge-shaped domains in domain evolution. Wedge-shaped domains turn into small domains with curved domain walls after the heating cycle and then become lamellar domains after the poling cycle at RT. Transitional domain structures with an increased density of nanodomains appear in both the thermal and poling cycles. More interestingly, the electric-field-dependent domain structure evolution at different temperatures shows better domain structure reversibility at high temperatures than at temperatures close to the phase boundary. This demonstrates that the BZT-0.5BCT ceramic has superior stability at medium temperatures (40 °C–60 °C), implying excellent stability for applications.

Structural, dielectric, ferroelectric and ferromagnetic properties in Fe-substituted BCT ceramics for energy storage and capacitor applications

Structural, dielectric, ferroelectric and ferromagnetic properties in Fe-substituted BCT ceramics for energy storage and capacitor applications

Synthesis and dielectric properties of BCT ceramics co-substituted by Sm3+ and Fe3+ for capacitor applications

Polycrystalline ferroelectric ceramics with compositional formula Ba0.70−x Ca0.30SmxTi1−xFexO3 (BCSTF) with (0, 0.005, 0.010, 0.015 and 0.020) were prepared by solid state reaction route and sintered at 1325 °C for 4 h. Single perovskite phase with tetragonal structure was confirmed from X-ray diffraction (XRD) analysis. The dielectric constant ‘ε’ and tangent loss ‘tanδ’ were studied for all the samples as a function of frequency (100 Hz to 100 kHz) and temperature (30–200 °C). A very small low ‘tanδ’ (0.9% at 100 kHz) was observed. The high value of temperature coefficient of capacitance ‘Tcc’ (~10%) was observed for all the BCSTF samples. P-E hysteresis loops were recorded for sample with x = 0.020 at different temperature. Electrocaloric effect ‘ECE’ was investigated and the temperature change ‘ΔT’ was found to be 0.53 K at 35 kV/cm with a high value of electrocaloric coefficient (0.15 K m/MV). The results show that the prepared ceramics can be useful in applications such as capacitor, dielectric bolometers, electrocaloric applications.

Flattening of free energy profile and enhancement of energy storage efficiency near morphotropic phase boundary in lead-free BZT-xBCT

We have synthesized lead-free BZT-xBCT (x = 0.45, 0.50 and 0.55) compositions near morphotropic phase boundary (MPB) using sol-gel technique. Here, we have reported the compositional effect of BCT concentration on structure, surface morphology, dielectric properties and energy storage capacity of BZT-xBCT ceramics. Scanning electron microscopy analysis suggests that the smallest grain size is found for the x = 0.55 composition. The dielectric constant vs temperature measurement indicates that the addition of BCT causes lowering of ordering temperature. In addition, we have performed modified Curie-Weiss fitting to reveal the microscopic behaviour of the synthesized compositions and found Curie constant ‘C’ as 1.3×106,2.1×107and1.7×107 for x = 0.45, 0.50 and 0.55 compositions, respectively, and diffusion coefficient 1.4≤γ≤1.99. Polarization (P) vs electric field (E) curves collected at series of temperature, insights that compositions x = 0.50 and 0.55 exhibit slimmer P-E profiles, which causes lowering of remnant polarization (Pr) and hysteresis loss of dielectric system and ensures their suitability in area of pyroelectric based energy harvesting. We also estimated the energy storage density W~189 mJ/cm3 and high discharge efficiency η~75.6% for BZT-0.55BCT ceramic composition. Further, we have employed Arrott plot approach to reveal the involved mechanism of Landau Free Energy flattening in BZT-BCT composition at MPB. It is considered that Landau Free Energy flattening plays key role in exhibiting high electro-mechanical response at MPB. On the basis of findings from dielectric spectroscopy and Arrott plot scheme, we argue that energy flattening phenomenon and high electromechanical response in BZT-xBCT system is achieved via active “polarization rotation mechanism”, instead of “polarization extension”. Our study emphasizes that BCT rich BZT-0.55BCT ceramics are suitable for high energy storage density application.

Factors affecting calcining temperatures of BZT–BCT ceramics

Piezoelectric ceramic 0.48Ba[Zr0.2Ti0.8]O3 – 0.52[Ba0.7Ca0.3]TiO3 (BZT–BCT) with nanostructure was manufactured with traditional ceramic technology. The nanostructure and the sintering aid reduce the calcining temperature from 1250 to 1170 °C and the sintering temperature from 1450 to 1350 °C. The piezoelectric properties of BZT–BCT at the optimal calcining and sintering temperature are discussed in detail.

A Large Piezoelectric Strain Recorded in BCT Ceramics Obtained by a Modified Pechini Method.

There is a strong need in the industry to develop lead-free piezoelectrics for sensors and actuators. Although these materials have become an important component of many electronic devices, it is very important for the industry to decarbonise ceramic technology, especially through the introduction of modern sintering technologies. Among the many piezoelectric compounds available, Calcium Barium Titanate (BCT) have been widely investigated because of its similar performance to lead-containing Lead Titanate Zirconate (PZT). In this paper, a modified Pechini method for obtaining ceramic Ba0.9Ca0.1TiO3 nano-powders is described. Deviation from the established procedure resulted in the precipitation of the solution or obtaining of a low-quality (poorly crystallized) product with numerous impurities. The samples of BCT materials were examined to find their ideal microstructures and structures; these factors were confirmed by their outstanding X-ray diffraction spectra and high piezoelectric constant values that are comparable to commercial lead-containing materials.

Porous sandwich structures based on BaZrTiO3–BaCaTiO3 ceramics for piezoelectric energy harvesting

Abstract In this study, porous sandwich structures based on barium zirconate titanate–barium calcium titanate (BZT–BCT) ceramics are investigated for energy harvesting applications. To improve the piezoelectric energy harvesting performance, porous sandwich structures based on the BZT–BCT ceramics produced by the tape casting method are designed to be optimum materials with high piezoelectric charge coefficient and low dielectric constant. The dense and porous layer are made of BZT–BCT ceramic sheets and a mixture of BZT–BCT ceramic and polyvinylidene fluoride (PVDF), respectively. Here, the PVDF is a sacrificial material that is volatilized in the burnout process, which results in the formation of pores within the microstructure. Depending on the volume fraction of the porous layer, the BZT–BCT ceramics are manufactured in proportions ranging from 0% to 100 vol%. The 20 vol% of the porous layer exhibits the highest figure of merit (FOM) of 4.53 p.m.2/N. When the volume fraction of the porous layer exceeds 20 vol%, the FOM sharply decreases. The stored energy is calculated by measuring the output voltage on the external capacitor (1 μF) through the full-bridge circuit connected to the specimen. The energy density is calculated by dividing the stored energy by the sample area. The sample with a 20 vol% of the porous layer has an energy density of 7.29 μJ/cm2, which is the highest value attained.

Effect of pore former sucrose on microstructure and electrical properties of porous BZT-0.5BCT ceramics

The present paper aims to study the effect of different pore forming agent on the density, porosity, pore morphology and electrical properties of porous BZT-0.5BCT ceramics. The electrical property evaluation is focused on dielectric constant, ferroelectric properties (P-E loop) and piezoelectric constant (d33 and g33) of the porous BZT-0.5BCT ceramics. BZT-0.5BCT powder was prepared by solid-state route. The porous ceramic was prepared by mixing BZT-0.5BCT with different percentage (10, 20, 30, 40 and 50 vol%) of polyvinyl alcohol (PVA) and sucrose as pore-forming agents (PFA). As a result, density, relative permittivity, remanent polarization and piezoelectric constant decreased linearly with increase in pore former addition. The pores derived from PVA and sucrose as pore former were spherical to irregular in shape. Isolated pores are observed up to 30 vol% of PFA addition and pore interconnectivity is observed at 40 vol% of PVA and sucrose addition. The decrease in electrical properties is much higher in sucrose when compared with PVA as a pore former.

Electrical and mechanical properties of BZT − xBCT lead‐free piezoceramics

AbstractIn this study, lead‐free (1 − x)Ba(Zr0.2Ti0.8)O3 − x(Ba0.7Ca0.3)TiO3 compositions are synthesized via conventional solid oxide route, and the ceramics are fabricated with normal sintering in air. The effects of composition fluctuations on dielectric, piezoelectric, and mechanical properties are investigated. The phase structure and the microstructure are analyzed with X‐ray diffraction and scanning electron microscopy. The best dielectric and piezoelectric properties of εr = 11 207 and d33 = 330 pC/N were obtained for BZT−0.35BCT and BZT−0.5BCT ceramics, respectively. The mechanical behavior—in terms of Vickers hardness and compressive and flexural strengths—was investigated, and the best mechanical behavior was found in the vicinity of the phase transition boundary with x values between 0.5 and 0.6.

Magnetic ion oxidation state dependent magnetoelectric coupling strength in Fe doped BCT ceramics.

Polycrystalline samples of Ba0.96Ca0.04Ti0.91Fe0.09O3 were prepared using a conventional solid state reaction route with different Fe starting precursors (Fe2O3, Fe3O4). The Rietveld refined XRD data confirmed the phase purity and tetragonal crystal structure of both the samples. The average grain size measured using SEM was ≈0.40 μm in both the samples. XPS analysis confirmed the presence of only Fe2+ and both Fe2+/Fe3+ in Fe2O3 and Fe3O4 doped BCT samples. The Pr and Mr values have been measured to be 1.34 μC cm−2, 2.88 μC cm−2 and 0.0015 emu g−1 and 0.135 emu g−1 in Fe2O3 and Fe3O4 doped BCT samples, respectively. The Fe3O4 doped samples exhibit much better M-E coupling (≈22%) as compared to Fe2O3 (≈7%) doped BCT samples. The results obtained hence suggest that Fe3O4 doping in BCT is better suited for multiferroic applications.

Enhanced ferroelectricity in relaxor $$\hbox {0.7BiFeO}_{{3}}{-}0.3(\hbox {Ba}_{0.85}\hbox {Ca}_{0.15})\hbox {TiO}_{{3}}$$ ceramics using ball milling technique

$$\hbox {0.7BiFeO}_{{3}}{-}0.3(\hbox {Ba}_{0.85}\hbox {Ca}_{0.15})\hbox {TiO}_{{3}}$$ (BF–BCT) ceramics were synthesized with a conventional solid-state reaction method. The electrical properties of the BF–BCT ceramics depend on the milling time via a planetary ball-milling technique. The results show that the sample prepared by milling for 40 h possesses a rather large remanent polarization of $$52 \,\upmu \hbox {C}/\hbox {cm}^{2}$$ and this value is superior to that of Non-Pb BF-based ceramics at room temperature. Moreover, the values of remanent polarization were confirmed by a PUND measurement to eliminate the contribution of leakage current. We attributed the large remanent polarization to the decrease in oxygen vacancies confirmed by X-ray photoelectron spectroscopy results. Moreover, the BF–BCT ceramics exhibit the dielectric relaxation process caused by the diffusion of oxygen vacancies inside ceramics.

Enhanced energy storage property in glass-added Ba(Zr0.2Ti0.8)O3-0.15(Ba0.7Ca0.3)TiO3 ceramics and the charge relaxation

Abstract Glass additive BaO-SrO-TiO2-Al2O3-SiO2-BaF2 is employed to enhance the microstructures and energy storage properties of the Ba(Zr0.2Ti0.8)O3-0.15(Ba0.7Ca0.3)TiO3 ceramics. To clarify the energy storage mechanism, the charge transportation and polarization process are investigated by thermally simulated depolarization current (TSDC). The dielectric breakdown strength increases from 4.3 kV/mm to 10.8 kV/mm for BZT-0.15BCT ceramics with 11 wt% glass additives, indicating that glasses could refine the grain size, uniform the structure, and decrease defects. Due to the micro-domain region, dielectric relaxation behavior is observed with a broadened and reduced dielectric constant peak at a large dielectric constant of about 3000 at room temperature. The largest charge energy density of 1.45 J/cm3 and discharge density of 0.17 J/cm3 are achieved for BZT-0.15BCT glass ceramics with 7 wt% glass additives. TSDC results demonstrate that dipole origin movement and charge transportation have an important effect on the dielectric properties and dielectric breakdown strength, respectively, which are largely influenced by the defects distribution state at the interfaces. Moderate domain walls could restrain the defects to inhibit the charge transportation and are harmful for the dielectric properties inversely. To achieve excellent energy storage performance, moderate domain walls are compromise of slightly degrading dielectric properties and greatly improving dielectric breakdown strength.

Composition-dependent xBa(Zr0.2Ti0.8)O3-(1-x)(Ba0.7Ca0.3)TiO3 bulk ceramics for high energy storage applications

This work reports the composition dependent microstructure, dielectric, ferroelectric and energy storage properties, and the phase transitions sequence of lead free xBa(Zr0.2Ti0.8)O3-(1-x)(Ba0.7Ca0.3)TiO3 [xBZT-(1-x)BCT] ceramics, with x = 0.4, 0.5 and 0.6, prepared by solid state reaction method. The XRD and Raman scattering results confirm the coexistence of rhombohedral and tetragonal phases at room temperature (RT). The temperature dependence of Raman scattering spectra, dielectric permittivity and polarization points a first phase transition from ferroelectric rhombohedral phase to ferroelectric tetragonal phase at a temperature (TR-T) of 40 °C and a second phase transition from ferroelectric tetragonal phase - paraelectric pseudocubic phase at a temperature (TT-C) of 110 °C. The dielectric analysis suggests that the phase transition at TT-C is of diffusive type and the BZT-BCT ceramics are a relaxor type ferroelectric materials. The composition induced variation in the temperature dependence of dielectric losses was correlated with full width half maxima (FWHM) of A1, E(LO) Raman mode. The saturation polarization (Ps) ≈8.3 μC/cm2 and coercive fields ≈2.9 kV/cm were found to be optimum at composition x = 0.6 and is attributed to grain size effect. It is also shown that BZT-BCT ceramics exhibit a fatigue free response up to 105 cycles. The effect of a.c. electric field amplitude and temperature on energy storage density and storage efficiency is also discussed. The presence of high TT-C (110 °C), a high dielectric constant (εr ≈ 12,285) with low dielectric loss (0.03), good polarization (Ps ≈ 8.3 μC/cm2) and large recoverable energy density (W = 121 mJ/cm3) with an energy storage efficiency (η) of 70% at an electric field of 25 kV/cm in 0.6BZT-0.4BCT ceramics make them suitable candidates for energy storage capacitor applications.

Effects of Excess Barium on the Structure and Electrical Properties of (Ba,Ca)TiO3 Piezoelectric Ceramics with High Mechanical Quality Factors

Manganese-doped Ba0.925Ca0.075TiO3 lead-free piezoelectric ceramics (abbreviated as BCT) with high mechanical quality factor were synthesized by conventional solid-state reaction method. The effects of excess Ba on the crystal structure, microstructure, and electrical properties of the ceramics were systematically investigated. X-ray diffraction and Raman spectra revealed that Ca2+ ions were pushed from Ba sites to Ti sites of BCT when 1.5 mol% extra Ba2+ ions were added after sintering. The grain size of the ceramics was decreased by adding extra Ba2+ ions. The mechanical quality factor and resistivity of the ceramics decreased dramatically when the excess Ba was more than 1.5 mol%. High piezoelectric coefficients ( d33 = 150–190 pC/N ) and high mechanical quality factors ( Qm = 1 000–1 200 ) were obtained in the ceramics when the excess of Ba was between 0.5 mol% and 1 mol%. These results indicated that the properties of BCT ceramics could be tailored by adjusting the content of Ba.