Electrocaloric Responsivity Research Articles

Integrated structural and functional analysis of Ba1-xSrxTiO3-Bi0.5Na0.5TiO3 ceramics: Insights into energy storage and electrocaloric performance

This paper reports an extensive investigation on the structural, dielectric, ferroelectric and pyroelectric properties of 0.7Ba1-xSrxTiO3 – 0.3Bi0.5Na0.5TiO3 (x = 0.0, 0.5, 0.6, 0.7) ceramics synthesized via conventional solid-state reaction (SSR) technique. X-ray diffraction data confirms the presence of pure perovskite phase. The variation of lattice parameters with strontium concentration in 0.7Ba1-xSrxTiO3 – 0.3Bi0.5Na0.5TiO3 ceramics were evaluated using the Rietveld refinement of the XRD data. The variation of dielectric permittivity with temperature (ε' ∼ T) shows the diffused phase transition and all the parameters related to the relaxor ferroelectrics (relaxation coefficient, activation energy and freezing temperature) were evaluated. The energy storage properties of the as-prepared ceramics were evaluated using the room temperature PE loop. Amongst the as-prepared ceramics, the composition with x = 0.5 possesses the highest energy storage density of 0.46 J/cm3 with an efficiency of 90 %. The temperature dependent P-E loops were used to study the electrocaloric effect (ECE). The ECE calculations were performed using in-direct method based on Maxwell's thermodynamic relations. A maximum adiabatic temperature change of 0.32 K is achieved at 268 K under a small applied electric field of 25 kV/cm for the ceramic with Sr content x = 0.5. Additionally, electrocaloric responsivity ξmax = 0.13 K mm/kV was also found for the studied ceramics. The above results show that the ceramic 0.7Ba1-xSrxTiO3 – 0.3Bi0.5Na0.5TiO3 with the composition x = 0.5 is a viable lead-free option for application in solid state refrigeration.

An in-depth comparison of dielectric, ferroelectric, piezoelectric, energy storage, electrocaloric, and piezocatalytic properties of Ba0.92Ca0.08Zr0.09Ti0.91O3 and Ba0.92Ca0.08Sn0.09Ti0.91O3 piezoceramics

The futuristic technology demands materials exhibiting multifunctional properties. Keeping this in mind, an in-depth investigation and comparison of the dielectric, ferroelectric, piezoelectric, energy storage, electrocaloric, and piezocatalytic properties have been carried out on Ba0.92Ca0.08Zr0.09Ti0.91O3 (BCZT) and Ba0.92Ca0.08Sn0.09Ti0.91O3 (BCST) lead-free compounds synthesized through the conventional solid state reaction method. Further, the Rietveld refinement against the XRD patterns affirmed the coexistence of orthorhombic (Amm2) and tetragonal (P4mm) phases at room temperature for both compounds. While BCZT compound demonstrated remarkable dielectric, piezoelectric, and piezocatalytic characteristics with maximum dielectric constant () ≈ 13304 near the Curie temperature ( ≈ 105 °C), converse piezoelectric coefficient ≈ 609 pm V-1 , power density () ≈ 89.71 KW cm-3 at room temperature, and 82.7 % Rhodamine B (RhB) dye degradation capability; on the other hand, BCST compound exceled in superior energy storage density () ≈ 191.8 mJ cm-3 with efficiency η ≈ 73.26% near room temperature and enhanced electrocaloric properties with adiabatic temperature change ≈ 0.980 K, isothermal entropy change ≈ 1.15 J Kg-1K-1 and a higher electrocaloric responsivity ) ≈ 0.49 K mm kV-1. These distinctions arise from the difference in ionic radii, lattice distortion, and the electronic configurations of the dopant ions, leading to a greater polarization change and a lower coercive electric field in the BCST ceramic. The outcome of the present study provides valuable insights for selecting a dopant tailored compound for specific application and underscores the potential of such ceramics in energy storage, piezocatalysis, and the development of advanced solid-state cooling devices for future applications.

Morphotropic phase boundary evolution with synergistic effect of sintering temperature to improve electrocaloric and energy storage performances of lead-free Ba0.95Ca0.05Sn0.09Ti0.91O3 (BCST) ceramic

The designing of lead-free ferroelectric ceramics for application in environment-friendly efficient electrocaloric cooling and energy storage devices is still challenging and need to be considered. A major challenge, however, is how to simultaneously achieve higher polarization and low hysteresis loss at low applied electric field. In this perspective, we comprehensively investigated sol-gel derived Ba0.95Ca0.05Sn0.09Ti0.91O3 (BCST) ceramics by varying the sintering temperature to explore its electrocaloric and energy storage capabilities. The excellent ∆T ∼ 1.03 K, ∆S ∼ 1.32 J/kg.K and high electrocaloric responsivity ΔT/ΔE ∼ 0.34 K.mm/kV at very low applied electric field of 30 kV/cm are obtained for pristine BCST sample sintered at 1400 °C. Additionally, we observed Wrec ∼ 136.18 mJ/cm3 and giant energy conversion efficiency η ∼ 94.29 % under very low applied electric field of 30 kV/cm for the same BCST sample. Our results reveal that control of sintering temperature contributes to a favorable and stable microstructure, including R-O-T phase coexistence and substitutional heterogeneity-induced nano-polar regions (PNRs) which strengthens the Polarization and supports the thin hysteresis loop. Thus all these factors simultaneously contributing to make BCST ceramic as a potential material for applications in advanced electrocaloric cooling and energy storage capacitors.

Enhanced electrocaloric response and energy storage in [(Bi0.5Na0.5)0.94Ba0.06]0.975Sr0.025TiO3 ceramic close to room temperature

Lead-free [(Bi0.5Na0.5)0.94Ba0.06]0.975Sr0.025TiO3 (BNBTS25), with morphotropic phase boundary, has attracted considerable attention due to its depolarization temperature, Td (Ferroelectric (FE)- Antiferroelectric (AFE) transition), which is in close proximity to room temperature (322K). Therefore, the research on electrocaloric and energy storage was limited to temperatures ranging from 223K to 363K. BNBTS25 presents firstly an intensive interests as promising candidate for environmental-friendly energy storage products. This material provides a good recoverable energy density up to Wrec = 577 mJ/cm3 with an energy-storage efficiency of η = 68% in the vicinity of Td. The origin of enhanced energy storage performance is discussed from a scientific point of view. Secondly, BNBTS25 exhibits a high electrocaloric effect (ECE), including an adiabatic temperature change of ΔT = 1.24 K and an electrocaloric responsivity of ξ = 0.301K.mm/kV was observed under an electric field of E = 40 kV/cm at a temperature near 290K. This high ECE performance exceeds that of several reported lead-free ceramics and even performs better than some lead based ceramics. The obtained results suggest that BNBTS25 ceramic is a promising candidate for both electrocaloric and energy storage applications in operating temperature such as cooling in microelectronic devices.

Enhancement of the electrocaloric effect in the 0.4BCZT-0.6BTSn ceramic synthesized by sol-gel route

The lead-free ferroelectric 0.4Ba0.85Ca0.15Zr0.10Ti0.90O3–0.6BaTi0.89Sn0.11O3 (0.4BCZT–0.6BTSn) ceramics were successfully prepared by the sol–gel process. Raman spectroscopy was used to examine the structural properties of the 0.4BCZT-0.6BTSn sample. The findings indicate that the sample was well crystallized into a single perovskite structure. The phase transitions of the studied sample have been investigated using the DSC technique. The electrocaloric effect (ECE) properties were indirectly determined using the Maxwell approach. Under a relatively low applied electric field of 30 kV cm−1, the results show enhanced electrocaloric temperature change and entropy change of ΔT = 1.32 K and ΔS = 1.41 J/kg.K, respectively. Besides, the electrocaloric responsivity (ξ max = 0.45 K·mm/kV) obtained is among the highest reported values in pb-free ferroelectrics near room temperature. These findings demonstrate that the lead-free 0.4BCZT–0.6BTSn ceramic is a promising candidate for solid-state cooling applications.

The electrocaloric effect of lead-free Ba1−yCayTi1−xHfxO3 from direct and indirect measurements

We report on the dielectric and electrocaloric properties of Ba1−yCayTi1−xHfxO3 for compositions 0.12 < x < 0.18 and y = 0.06, as well as x = 0.15 and 0 < y < 0.15, synthesized by the conventional solid-state reaction method. The addition of Hf/Ca broadens the ferroelectric-paraelectric phase transition while moving it toward room temperature. Two interferroelectric transitions are seen to converge, together with the ferroelectric–paraelectric phase transition, at ∼335 K for 0.12 < xc < 0.135 and y = 0.06. Consistent with the dielectric properties, the electrocaloric effect maximizes closer to room temperature with increasing Hf/Ca substitutions, which promote larger temperature spans. The electrocaloric responsivity gradually decreases from 0.2 to 0.1 K mm kV−1 with the addition of Hf/Ca. A homemade quasi-adiabatic calorimeter is employed to measure “directly” the electrocaloric data, which are also calculated from polarization-versus-electric-field cycles using “indirect” standard procedures. The comparison between measured and calculated values highlights the importance of having access to direct methods for a reliable determination of the electrocaloric effect.

Energy storage and electrocaloric properties of lead free (1‐x)(0.6Ba(Zr0.2Ti0.8)O3‐0.4(Ba0.7Ca0.3)TiO3)–xBiZn0.5Ti0.5O3 ferroelectric ceramics

In the present work, we investigated the effect of BiZn0.5Ti0.5O3 composition on energy storage and electrocaloric properties of lead free (1-x)(0.6Ba(Zr0.2Ti0.8)O3‐0.4(Ba0.7Ca0.3)TiO3)–xBiZn0.5Ti0.5O3 [BZCT-BZ] ceramics by varying the x from 0 to 10%. The x-ray diffraction (XRD) analysis evidences the formation of BZCT-BZ solid solution without any secondary or impurity phase. The peaks splitting at 2θ = ∼ 45° and 66° suggested the co-existence of rhombohedral (R) and tetragonal (T) phases (morphotropic phase boundary) at room temperature for x ≤ 1%. Further, BZCT-BZ ceramics with x > 1% exhibited pseudocubic nature. The ferroelectric hysteresis loop confirms relaxor behavior and the decrease in remanent polarization with increase of BZ content is explained based on the back switching calculations. The BZCT-BZ ceramics as function of BZ composition gave the optimum recoverable energy density of 197 mJ/cm3 and an efficiency of 92% at an applied field of 45 kVcm−1. Such an exceptionally high energy storage efficiency is attributed to the enhanced relaxor behavior and superior back switching capability. Further, the values of electrocaloric temperature change and responsivity are found to be 0.67 K at 45 kV/cm and 0.014 Kcm/kV respectively in 0.98BZCT-0.02BZ ceramics. Thus, BZCT-BZ ceramics are appealing candidates for energy storage and electrocaloric application.

Effect of MgO doping on energy storage and electrocaloric properties of ferroelectric 0.6Ba(Zr0.2Ti0.8)O3–0.4(Ba0.7Ca0.3)TiO3 ceramics

This study highlights the effect of MgO doping on microstructure, dielectric, ferroelectric, energy storage and electrocaloric properties of lead-free (1-x)(0.6Ba(Zr0.2Ti0.8)O3–0.4(Ba0.7Ca0.3)TiO3)–xMgO ceramics with x varying from 0-5%. X-ray diffraction studies revealed that BZCT-MgO ceramics exhibited a morphotropic phase boundary (MPB), i.e. coexistence of both tetragonal and rhombohedral phases at room temperature for x ≤ 1%. Scanning electron microscope (SEM) images revealed that grain size is decreased with the increase of MgO content. The Raman analysis and temperature dependent dielectric studies further confirm the MPB behaviour at low MgO content. Besides, the MgO additive improves the diffused phase transition (DPT) behaviour of BZCT ceramics, lowers transition temperature and enhances their relaxor behaviour. It is observed that 0.99BZCT–0.01MgO showed optimum energy storage properties with a recoverable energy density of 177.6 mJ/cm3 and an efficiency of 79% at an electric field of 45 kV/cm. Moreover, they exhibited a robust energy storage performance even after passing 107 cycles. Further, the electrocaloric temperature change and responsivity are found 1.12 K at 45 kV/cm and 0.024 Kcm/kV, respectively in 0.99BZCT–0.01MgO ceramics.

Electrocaloric effect at special points in the composition-temperature-electric field phase diagram of barium zirconate-titanate (BZT)

The composition-temperature-electric field diagram and electrocaloric properties of BaTi1−xZrxO3 (BZT) were computed using a self-consistent phenomenological approach. By subtracting contributions from the latent heat, the adiabatic temperature change due solely to the material polarization was quantified on passing through critical end, tricritical and phase convergence points. The largest temperature change occurs at the first-order paraelectric to ferroelectric transitions where the latent heat is triggered, but the material polarization contribution is greatest at the critical temperature. The maximum electrocaloric responsivity occurs at a field 1.25 times greater than the critical field. The temperature change increases at the tricritical point due to a field-induced tetragonal to rhombohedral transformation, but the responsivity diverges due to vanishing of the critical field. The enhanced temperature change observed experimentally near the convergence point is attributed to greater polarization change in the rhombohedral phase, and to a polar glasslike state that contributes to the dipolar configurational entropy.

Role of Density and Grain Size on the Electrocaloric Effect in Ba0.90Ca0.10TiO3 Ceramics.

Pure perovskite Ba0.90Ca0.10TiO3 ceramics, with a relative density of between 79 and 98% and grain sizes larger than 1 µm, were prepared by solid-state reaction. The dielectric and electrocaloric properties were investigated and discussed considering the density and grain size of the samples. Room temperature impedance measurements show good dielectric properties for all ceramics with relative permittivity between 800 and 1100 and losses of <5%. Polarization vs. E loops indicates regular variation with increasing sintering temperature (grain size and density), an increase in loop area, and remanent and saturation polarization (from Psat = 7.2 µC/cm2 to Psat = 16 µC/cm2). The largest electrocaloric effect was 1.67 K for ceramic with GS = 3 µm at 363 K and electrocaloric responsivity (ζ) was 0.56 K mm/kV. These values are larger than in the case of other similar materials; thus, Ba0.90Ca0.10TiO3 ceramics with a density larger than 90% and grain sizes of a few µms are suitable materials for electrocaloric devices.

Electrocaloric effect in lead-free Ba1-xLn2x/3Ti0.925(Yb0.5Nb0.5)0.075O3 ceramics (Ln = Eu3+, Nd3+, Pr3+ and x = 0, 0.005)

This study reports on the electrocaloric effect in lead-free Ba1-xLn2x/3Ti0.925(Yb0.5Nb0.5)0.075O3 ceramics (where Ln = Eu3+, Nd3+, Pr3+), which was evaluated by an indirect method. The electrocaloric temperature change (ΔT) was estimated from the Maxwell relation based on measured P-E hysteresis loops recorded at different temperatures. For x = 0, the electrocaloric temperature change (ΔT) was about 0.052 K (7.95 kV/cm, 326 K), while they were 0.011 K (3.97 kV/cm and 338 K), 0.019 K (3.97 kV/cm and 332.5 K), and 0.622 K (28 kV/cm and 360 K) for the Eu 3+, Nd3+, and Pr3+ doped BaTi0.925(Yb0.5Nb0.5)0.075O3 (x = 0.005), respectively. The electrocaloric responsivity ξ = ΔT/ΔE, as calculated, reveals that the Ba0.995Pr0.005Ti0.925(Yb0.5Nb0.5)0.075O3 (BTYN: Pr3+) ceramic exhibits the largest value, of about 0.222 Kmm/kV, reported so far in the BTYN-based lead-free ceramics. As a result of this finding, the lead-free BTYN: Pr3+ system seems to be one of the best options for future electrocaloric applications as a lead-free alternative to lead-based materials.

Large Electrocaloric Responsivity and Energy Storage Response in the Lead-Free Ba(GexTi1-x)O3 Ceramics.

Ferroelectric property that induces electrocaloric effect was investigated in Ba(GexTi1−x)O3 ceramics, known as BTGx. X-ray diffraction analysis shows pure perovskite phases in tetragonal symmetry compatible with the P4mm (No. 99) space group. Dielectric permittivity exhibits first-order ferroelectric-paraelectric phase transition, confirmed by specific heat measurements, similar to that observed in BaTiO3 (BTO) crystal. Curie temperature varies weakly as a function of Ge-content. Using the direct and indirect method, we confirmed that the adiabatic temperature change ΔT reached its higher value of 0.9 K under 8 kV/cm for the composition BTG6, corresponding to an electrocaloric responsivity ΔT/ΔE of 1.13 × 10−6 K.m/V. Such electrocaloric responsivity significantly exceeds those obtained so far in other barium titanate-based lead-free electrocaloric ceramic materials. Energy storage investigations show promising results: stored energy density of ~17 mJ/cm3 and an energy efficiency of ~88% in the composition BTG5. These results classify the studied materials as candidates for cooling devices and energy storage applications.

Enhanced electrocaloric effect and energy storage response in lead-free (1-x)K0.5Na0.5NbO3 - xBaTiO3 ferroelectric ceramics

Ferroelectric/antiferroelectric materials are demanded for the development of future eco-friendly high-efficient electrocaloric refrigeration technology and energy-storage devices. Here, we report the electrocaloric effect (ECE) and an energy storage response in lead-free (1-x)K0.5Na0.5NbO3-xBaTiO3 (KNN-xBT) ferroelectric solid solution ceramics with x = 0.04, 0.06, 0.08, and 0.10 synthesized via the traditional solid-state route. The XRD and Raman spectroscopy investigations confirmed the coexistence of orthorhombic and tetragonal phases. The BT substitution has shifted the phase transitions of KNN towards the lower temperature side and also helped to diffuse the phase transitions. The maximum value of the ECE (ΔTmax), electrocaloric responsivity (ΔT/ΔE) and the recoverable energy density (Wrec) were evaluated to be around 0.70 K, 1.75 × 10−7 KmV−1 and 0.22 Jcm−3, respectively in KNN–xBT ceramics for x = 0.08 at an applied electric field of 40 kVcm−1. This study suggested that KNN-xBT material is an attractive ferroelectric material for potential applications in the design of ozone-friendly solid-state freezing technology and energy-storage devices.

Enhanced electrocaloric response and energy storage performance of Li‐substituted BaTiO3 ceramics

AbstractRecently, ferroelectric and antiferroelectric ceramic materials have gained a lot of interest for the development of environment‐friendly highly‐efficient electrocaloric refrigeration and energy‐storage devices. In this work, lead‐free Ba1−xLixTiO3 ceramics with x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05 were synthesized by the conventional solid‐state reaction method, and the effect of Li doping on dielectric, leakage current, ferroelectric, electrocaloric, and energy storage properties of BaTiO3 ceramics was systematically investigated. The XRD and Raman studies confirmed that the structure of Ba1−xLixTiO3 remains tetragonal as for BaTiO3. The Li substitution shifted the phase transition (TC) of BaTiO3 slightly towards the lower temperature side. Significant drop in leakage current was observed with an addition of Li content. The maximum values of the electrocaloric effect (ΔT), electrocaloric responsivity, and coefficient of performance were found to be 1.44 K, 0.24 × 10−6 K m/V, and 5.75, respectively, for x = 0.04 at an applied field of 60 kV/cm near the Curie temperature. The maximal value of energy storage density was found to be 0.42 J/cm3 with an energy storage efficiency of 60% for x = 0.05. Our results suggested that lead‐free Ba1−xLixTiO3 ceramic material is a promising candidate for potential applications in solid‐state refrigeration technology and high‐efficiency energy storage devices.

Impact of annealing on electrocaloric response in Lanthanum-modified lead zirconate titanate ceramic

Over the past decades, there has been significant interest in new cooling technology based on the large electrocaloric effect observed in polymeric and inorganic ferroelectric materials. We report a dramatic impact of annealing on the electrocaloric effect observed by direct measurements in Pb0.88La0.12(Zr0.65Ti0.35)0.97O3 bulk ceramics (12/65/35 PLZT). In addition, the EC response was measured deep in a relaxor part of the PLZT composition phase diagram. After additional one-hour sample annealing at 600 °C, the EC response increased by about six times. Electrocaloric results confirm the existence of the significant electrocaloric response with the EC temperature change (ΔTEC) of 4.5 K at 360 K and 90 kV/cm in an annealed sample. This value exceeds previously obtained maximum ΔTEC values at the same field in perovskite relaxor ferroelectrics such as Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) and 8/65/35 PLZT ceramics. The electrocaloric responsivity ΔT/ΔE = 5.09 × 10−7 Km/V determined at 360 K is among the highest observed in bulk perovskite ferroelectrics at a relatively high electric field of 90 kV/cm.

Improved energy storage and electrocaloric properties of lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramic

Lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramic powders were synthesized using the sol–gel method. The ceramics thickness was reduced to achieve high-energy storage and large electrocaloric effect in bulk ceramics. Dielectric, ferroelectric, energy storage, and electrocaloric properties were investigated for BCZT ceramic with 400 µm. Here, pure crystalline structure and homogenous microstructure were identified by XRD analysis and SEM measurements, respectively. The dielectric measurements revealed a maximum dielectric constant associated with ferroelectric–paraelectric phase transition. The maximum of $$\varepsilon^{\prime}_{{\text{r}}}$$ was 17841, around 352 K. Furthermore, the BCZT ceramic exhibited improved energy storage and electrocaloric properties. A high recoverable energy density Wrec of 0.24 J/cm3 and a total energy density Wtotal of 0.27 J/cm3 with an efficiency coefficient of ~ 88% at 423 K under an electric field of 55 kV/cm were obtained. Besides, The maximum value of ΔT = 2.32 K, the electrocaloric responsivity ζ = 0.42 K mm/kV, the refrigeration capacity RC = 4.59 J/kg and the coefficient of performance COP = 12.38 were achieved around 384 K under 55 kV/cm. The total energy density Wtotal and the temperature change ΔT were also calculated by exploiting the Landau–Ginzburg–Devonshire (LGD) theory. The theoretical results matched the experimental findings. These results suggest that the synthesized BCZT ceramic with reduced thickness could be a promising candidate for energy storage and electrocaloric applications.

Enhanced near-ambient temperature energy storage and electrocaloric effect in the lead-free BaTi0.89Sn0.11O3 ceramic synthesized by sol–gel method

Lead-free perovskite materials with high performance have high potential in clean energy storage applications and developments of electrocaloric devices. This work reports structural, dielectric, ferroelectric, energy storage, and electrocaloric properties near the ambient temperature in barium stannate titanate (BaTi0.89Sn0.11O3, BTS11) ceramic prepared by a sol–gel method. A single perovskite structure formation was confirmed using the X-ray diffraction analysis. Average grain size of 18.5 µm was found by the mean of the SEM micrograph with a density of 5.91 g/cm3. The multiphase coexistence at very near ambient temperature was proved using temperature-dependent micro-Raman measurements and differential scanning calorimetry. The BTS11 ceramic exhibits a high dielectric constant of 15,460 and a low dielectric loss (< 0.055) in a broad temperature range. Moreover, a high energy storage density of 122 mJ/cm3 was shown with an efficiency of 79%, a maximum value of electrocaloric temperature change (ΔT) of 0.86 K, and finally, an electrocaloric responsivity (ΔT/ΔE) of 0.24 K.mm/kV at the external electric field change of 35 kV/cm near ambient temperature. The enhanced dielectric, ferroelectric, and electrocaloric properties make BTS11 ceramics a great candidate for solid-state cooling technology and high energy storage applications near ambient temperature.

Improvement of the electrocaloric effect and energy storage performances in Pb-free ferroelectric Ba0.9Sr0.1Ti0.9Sn0.1O3 ceramic near room temperature

Perovskite-type Ba0.9Sr0.1Ti0.9Sn0.1O3(BSTSn) ceramic was synthesized by the sol-gel method. The P-E hysteresis loops were recorded at different temperatures to investigate the ferroelectric and energy storage properties of BSTSn ceramic. Enhanced recoverable energy density and high energy storage efficiency were found to be 58.08 ​mJ/cm3 and 84.36%, respectively at room temperature (RT) under a moderate applied electric field of 20 ​kV/cm. The electrocaloric effect (ECE) in the BSTSn ceramic was explored using two different approaches based on P–E hysteresis loops, and pyroelectric current measurements. The largest electrocaloric (EC) temperature change, ΔTmax ​≈ ​0.63 ​K was determined using the Maxwell relationship obtained near RT under 20 ​kV/cm. The corresponding EC responsivity (ξmax) value of 0.31 ​K ​mm/kV is one of the highest reported values in lead-free ferroelectrics near RT. This study demonstrates that the BSTSn ceramic is a promising candidate for solid-state cooling and energy storage applications.

Nanostructured BaTi1-xSnxO3 ferroelectric materials for electrocaloric applications and energy performance

Nanostructured BaTi1-xSnxO3 (x = 0, 0.05 & 0.075) were successfully synthesized using the modified Pechini processing method. The phase purity and symmetry were examined by X-ray diffraction and Raman spectroscopy. Tetragonal symmetry was obtained for BaTiO3 (BT) while orthorhombic symmetry for Sn doped BT. BT exhibits an up-shift of the Curie temperature towards high temperatures (TC = 139 °C). In contrast, a down-shift was recorded for Sn doped BT. Then, indirect electrocaloric (EC) adiabatic temperature change ΔT and the energy storage performances were determined based on ferroelectric hysteresis loops. Interestingly, large EC responsivity of ΔT/ΔE = 0.81 × 10−6 K m/V was obtained for the BT accompanied with a moderate stored energy of 23 mJ/cm3 but with a high energy efficiency of 67%. The incorporation of Sn in BT was found to broaden the EC responsivity and to improve the energy efficiency up to 90%, recorded for the 5% Sn doped BT.

Enhanced electrocaloric and energy-storage properties of environment-friendly ferroelectric Ba0.9Sr0.1Ti1−xSnxO3 ceramics

The electrocaloric (EC) effect and energy storage properties of eco-friendly ferroelectric Ba0.9Sr0.1Ti1−xSnxO3 (BSTS-x) ceramics prepared by the conventional solid-state reaction method were studied. Significant energy efficiency exceeding 80% was found in our samples. In particular, BSTS-5 and BSTS-10 samples exhibit 92% and 88% efficiency, respectively, over a wide temperature range around room temperature (RT). Direct EC measurement and an indirect method based on the thermodynamic approach were used to characterize the EC effect, and both yielded consistent results. The largest electrocaloric responsivity of 0.73 K mm/kV was obtained for BSTS-0 at 368 K with an adiabatic temperature change ΔTEC of 0.55 K at a low applied electric field of only 7.4 kV/cm. With increasing Sn-content, the EC response of BSTS-x ceramics decreases, while their diffuseness increases over an extensive temperature range, centered at RT. A significant coefficient of performance (COP > 26) was found for our samples. The obtained results demonstrate the possibility of designing eco-friendly materials with higher EC effect and energy efficiency for potential solid-state refrigeration and energy storage devices.