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(Zr_0.2Ti_0.8)O₃-(1-x)(Ba_0.7Ca_0.3)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 (T_R-T) of 40?°C and a second phase transition from ferroelectric tetragonal phase - paraelectric pseudocubic phase at a temperature (T_T-C) of 110?°C. The dielectric analysis suggests that the phase transition at T_T-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 (P_s) ≈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 T_T-C (110?°C), a high dielectric constant (ε_r ≈?12,285) with low dielectric loss (0.03), good polarization (P_s ≈?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.     

Enhanced piezoelectric,electrocaloric and energy storage properties at high temperature in lead-free Bi0.5(Na1-xKx)0.5TiO3 ceramics

The piezoelectric, electrocaloric and energy storage properties were systemically investigated in lead-free Bi_0.5(Na_1-xK_x)_0.5TiO₃ ceramics from room temperature to high temperature region. These ceramics can be poled completely to obtain large piezoelectric coefficient (104–153 pC/N) at low electric field of ~30?kV/cm. The piezoelectric property shows good thermal stability due to high depolarization temperature (T_d). For BNKT₂₀, a large low electric field-induced strain of 0.36% is obtained at 120?°C under 50?kV/cm, the corresponding normalized strain coefficient is up to 720?pm/V, which is larger than other BNT-based ceramics at high temperature region. The electrocaloric properties of these ceramics are studied via indirect and direct methods. Large EC value (~1.08?K) in BNKT₂₀ ceramic is obtained at 50?kV/cm using indirect calculation. Above 100?°C, the dielectric energy storage density and efficiency of BNKT₂₀ is still up to ~0.85?J/cm³ and 0.75, respectively. The BNKT_x ceramics may become promising candidates in the fields of actuators, electrocaloric cooling and energy storage at high temperature region.     

Improvement of dielectric breakdown strength and energy storage performance in Er2O3–modified 0.95Sr0.7Ba0.3Nb2O6-0.05CaTiO3 lead-free ceramics

In this study, 0.95?Sr_0.7Ba_0.3Nb₂O₆-0.05CaTiO₃-x wt% Er₂O₃ ceramics (SBNCTEx; x?=?0–5) were synthesized using traditional solid-state method, and we investigated the microstructure, energy storage properties as well as the relationship between dielectric breakdown strength and interfacial polarization. As compared with pure 0.95?Sr_0.7Ba_0.3Nb₂O₆-0.05CaTiO₃ ceramics, the Er₂O₃ dopants suppressed the grain growth of SBNCTEx, and the doped ones showed the dense microstructure. The secondary phase was found for x?≥?1 according to the EDS results, and the influence of the secondary phase on relative dielectric breakdown strength has also been studied. The dielectric breakdown strength increased from 18.1?kV/mm to 34.4?kV/mm, which is good for energy storage. The energy storage density of 0.28?J/cm³ and the energy storage efficiency of 91.4% were obtained in the SBNCTE5 ceramics. The results indicate that SBNCTE ceramics can be used as energy storage capacitors.     

Compensation for volatile elements to modify the microstructure and energy storage performance of (W,Ni)-codoped Na0.5Bi0.5TiO3 ceramic films

This work reports the characteristics of nonstoichiometric Na_0.5+xBi_0.5+yTi_0.96W_0.01Ni_0.03O₃ (x?=?0.0%, y?=?1.0%; x?=?0.5%, y?=?2.0%; x?=?1.0%, y?=?4.0%) ceramic films derived from chemical solution deposition and the role played by excess Na/Bi in modifying microstructure and electrical properties. Single perovskite phase structure can be maintained in all compositions. Decreased grain size can be obtained with the increasing compensation for volatile Na/Bi elements. Particularly, extra amounts of 0.5?mol% Na and 2.0?mol% Bi leads to reduced leakage and enhanced ferroelectric polarization. Meanwhile, due to the high breakdown electrical field strength and large difference between maximum and remanent polarization, an excellent energy storage performance can be achieved in Na_0.505Bi_0.52Ti_0.96W_0.01Ni_0.03O₃ sample, which is distinguished by a recoverable energy storage density of 40.5?J/cm³ and an energy storage efficiency of 43.6% at 2515?kV/cm as well as a good frequency stability. Hence, the regulation for the content of volatile elements is effective to modify the electrical response of Na_0.5Bi_0.5TiO₃-based materials.     

Stable dielectric properties of Na1+xBiTi6O14+0.5x (x = −0.02, − 0.01, 0.01, 0.02) ceramics with low loss and high operating temperature

New lead-free dielectric ceramics, Na_1+xBiTi₆O_14+0.5x (x?=??0.02, ??0.01, 0.01, 0.02), were prepared by the conventional solid-state method. Micro-structural and electrical properties of Na_1+xBiTi₆O_14+0.5x were studied. XRD showed all the samples exhibited a single structured phase. Grains decreased at the beginning, then grew with the increasing x content in SEM. Impedance spectra (IS) analysis evidenced the phenomena that the dielectric permittivity increased firstly, then decreased, while the loss had the opposite trend. Z* plots showed that Na_1+xBiTi₆O_14+0.5x ceramics were a kind of dielectrics. The activation energy (E_a) could be calculated in the range of 1.53–1.65?eV, which indicated they were dielectric ceramics. Na_1+xBiTi₆O_14+0.5x ceramics (x?=?0.01) sintered at 1040?°C showed prominent dielectric properties with a dielectric constant of 25.76, loss of 0.07%, E_a of 1.65?eV, density of 3.463?g/cm³, impedance of 0.532?MΩ?cm, -Z′′_max of 0.1958?MΩ?cm, capacitance of 5.56?pF/cm (600?℃), which were enhanced much compared with other samples. The existence of dielectric properties with high dielectric constant, low dielectric loss and wide operating temperature range makes it possible to develop the ceramics into high-temperature capacitors.     

Enhanced energy-storage properties of (1-x)(0.7Bi0.5Na0.5TiO3-0.3Bi0.2Sr0.7TiO3)-xNaNbO3 lead-free ceramics

A series of (1-x)(0.7Bi_0.5Na_0.5TiO₃-0.3Bi_0.2Sr_0.7TiO₃)-xNaNbO₃ (BNT-BST-100xNN) lead-free ceramics were fabricated using conventional solid-state reaction technique. The phase behavior, microstructure, dielectric, ac impedance and energy-storage properties of the sintered ceramics were systematically investigated. XRD patterns and surface SEM micrographs revealed the introduction of NaNbO₃ didn't change the perovskite structure of BNT-BST at low doping level. The NaNbO₃ doping gave rise to slimmer P-E loops and thus gained enhanced energy storage properties. Therefore, a maximum energy storage density of 1.03 J/cm³ was achieved at 85 kV/cm at x = 0.01 via increasing the dielectric breakdown strength (DBS). Temperature-dependent dielectric permittivity illustrated the enhanced relaxor characteristics, implying the long-rang ferroelectric order was further damaged due to the introduction of NaNbO₃. The results above indicate the sintered ternary ceramics can be a promising lead-free candidate for energy storage capacitors.     

Effects of TiO2 addition on dielectric and energy storage properties of BaO-K2O-Nb2O5-SiO2 glass ceramics

In this work, 25.6BaO-6.4K₂O-32Nb₂O₅-36SiO₂-xTiO₂ (0 ≤ x ≤10 mol%) (BKNST) glass ceramics were synthesized by conventional melts and controllable crystallization method. The effects of different TiO₂ addition on the phase composition, dielectric and energy storage properties of BKNS glass ceramics were systematically evaluated. With the TiO₂ concentration increasing, a growing content of Ba₂TiO₄ phase was observed in the glass ceramics. The microstructures appeared to be homogenous and uniform with very low porosity through the addition of TiO₂, for which the maximal breakdown strength of 2112 kV/cm and the corresponding energy storage density of 9.48 J/cm³ were obtained with x = 7.5. The extremely low dielectric loss of less than 1‰ (25 °C, 100 kHz) and the obviously improved microstructure contributed to the increased breakdown strength. In addition, the discharge power density of the glass-ceramic capacitor (x = 7.5) was investigated using the RLC charge-discharge circuit and a relatively high value of 16 MW/cm³ at 300 kV/cm was obtained.     

Energy storage properties in Ba5LaTi3Ta7O30 tungsten bronze ceramics

Ba₅LaTi₃Ta₇O₃₀ tungsten bronze ceramics is a typical linear dielectric with high dielectric constant and low loss, which is expected as a promising candidate for energy-storage application. In the present work, energy-storage properties of Ba₅LaTi₃Ta₇O₃₀ tungsten bronze ceramics were investigated, and the dielectric breakdown mechanism was also discussed based on the morphology of the fracture surface. Dense ceramics were obtained by sintering at temperatures from 1500 to 1575°C. Both the dielectric constant and dielectric strength show strong dependences on the sample density. Optimal dielectric constant of 159, dielectric strength of 639 kV/cm, and energy storage density of 2.9 J/cm³ were obtained for ceramics sintered at 1550°C, that have the highest density and fine grains. The dielectric strength and energy storage density were also highly dependent on the sample thickness. For ceramics sintered at 1525°C, the dielectric strength increases from 283 to 585 kV/cm while the energy storage density increases from 0.5 to 2.3 J/cm³ when the thickness changes from 0.5 to 0.2 mm. A thermal breakdown mechanism was adopted to understand the breakdown process in the present ceramics.     

Combustion synthesis of high-performance high-entropy dielectric ceramics for energy storage applications

High-entropy dielectric ceramics have demonstrated a promising prospect for applications in energy storage recently. However, most high-entropy dielectrics synthesized by conventional solid-state reaction (SSR) method demonstrated unsatisfactory performance for energy storage. Therefore, it is meaningful to develop a feasible way to fabricate high-performance high-entropy dielectric ceramics. Herein, high-entropy (Sr_0.6Bi_0.2Na_0.2)(Ti_1-xZr_x/2Al_x/4Nb_x/4)O₃ ceramics are prepared by a solution combustion synthesis (SCS) method. The SCS fabricated ceramics (x = 0.25) demonstrate a high recoverable energy density of ∼4.46 J/cm³ at a high critical electric field of 520 kV/cm, a high energy efficiency ∼88.52%, a large power density of ∼176.65 MW/cm³ (at 400 kV/cm), an ultrafast discharge time of ∼48 ns, and a high Vikers hardness of ∼7.09 GPa. The key energy storage parameters are much better than those of the samples prepared by the SSR method owing to the absence of unexpected impurity phases, and the refined grain size at the submicrometer scale in our SCS fabricated high-entropy ceramics. The study provides a facile way to fabricate high-performance high-entropy dielectric ceramics for energy storage, indicating that the SCS routine is notably advantageous for preparing high-entropy dielectric energy ceramics.     

Crystal structures and microwave dielectric properties of low-firing Ca5Zn4-xMgxV6O24 ceramics

Ca₅Zn_4-xMg_xV₆O₂₄ (x?=?0–3) microwave dielectric ceramics with low sintering temperature were synthesized via the conventional solid-state reaction. Effects of the substitution of Mg²⁺ for Zn²⁺ on crystal structures and microwave dielectric properties were investigated. XRD and Rietveld refinement showed the solid solution single phase formed when 0?≤?x?≤?2, but a few ZnO was observed when x?=?3. Meanwhile, the lattice parameters were found to decrease monotonously with Mg content increasing. The vibration modes of Raman were confirmed and the relationship with microwave dielectric properties was analyzed. Appropriate substitution of Mg²⁺ improved the packing fraction, the cation ordering degree, and the Y-site bond valence, contributing to high Q×f and low | τ_f |. However, the ε_r reduced with the increasing content of Mg²⁺ due to the decrease of ion polarizability. Finally, the best microwave dielectric properties were achieved at x?=?2 with ε_r =?11.0, Q?×?f?=?66,365?GHz (at 10.0?GHz), and τ_f =??80.4?ppm/°C.     

Tunable electrocaloric and energy storage behavior in the Ce,Mn hybrid doped BaTiO3 ceramics

The electrocaloric effect and energy storage property are tuned in the Ba_1-xCe_xTi_0.99Mn_0.01O₃ ceramics prepared by the solid state reaction method. The ceramics with lower Ce content (x?=?0.005, 0.015) show a better ΔT and ΔT/ΔE response. The ceramics with higher Ce content (x?=?0.030, 0.040, 0.045) represent the broader ΔT peaks (50?K–60?K), and the higher energy storage density and efficiency. The largest electrocaloric response (ΔT_max?=?1.22?K, ΔT/ΔE?=?0.41?K mm/kV) is found in the Ba_0.995Ce_0.005Ti_0.99Mn_0.01O₃ ceramics, which is comparable or even higher than that of the most isovalent substituting BaTiO₃-based ceramics reported before. The maximum energy storage density 0.11?J/cm³ (E?=?30?kV/cm) is obtained for the Ba_0.970Ce_0.030Ti_0.99Mn_0.01O₃ ceramics, with high efficiency of 65–88% over a wide temperature range of 72?K. This work may open more opportunities to design high electrocalaric and energy storage performance lead-free systems from the viewpoint of the heterovalent and size mismatch substitution.     

Enhanced electrical properties in Nd and Ce co-doped CaBi4Ti4O15 high temperature piezoceramics

Lead-free piezoelectric material with excellent piezoelectric properties and high Curie temperature is necessary for practical applications. In this work, (Nd, Ce) co-doped CaBi₄Ti₄O₁₅ (CBT) ceramics were prepared by the conventional solid-state reaction technique. The effect of (Nd, Ce) co-doping on the structure and resulting electrical properties of CBT ceramics was systematically investigated. The optimized comprehensive performances were obtained at x?=?0.075 with a large piezoelectric coefficient (19 pC/N), a low dielectric loss (0.073%) and a high Curie temperature (794?°C). More importantly, the ceramic also maintained a very high resistance and a low dielectric loss even at 400?°C (ρ?=?2.5?×?10⁸ Ω?cm, tan δ?=?1.96%) and the d₃₃ showed no sign of waning after annealed at 400?°C, which shows great potential for high temperature piezoelectric device applications. Related mechanisms for the enhancement of electrical properties were discussed.     

Energy storage properties of MgO-doped 0.5Bi0·5Na0·5TiO3-0.5SrTiO3 ceramics

0.5Bi_0·5Na_0·5TiO₃-0.5SrTiO₃-x wt% MgO (x = 0, 0.5, 1.0, 1.5, 2.0, 3.0) ceramics were fabricated via solid-state method. The effect of MgO doped on energy storage properties, dielectric performance, phase structure and microstructures of 0.5Bi_0·5Na_0·5TiO₃-0.5SrTiO₃ (BNST) ceramics were studied systemically. The Mg²⁺ substituted Ti⁴⁺ site in BNST, which was confirmed by X-ray diffraction (XRD) result. The scanning electron microscope (SEM) images show that all the ceramic samples exhibit uniform and compact morphologies. The temperature dependent permittivity exhibits frequency dispersion, indicating that the ceramic samples are typical relaxor ferroelectrics. It was found that MgO doped BNST can significant improve the breakdown strength (E_b) of samples from 109 kV/cm to 227 kV/cm, which results in a great enhancement on energy storage density. The sample of x = 3.0 has the largest energy storage density (2.17 J/cm³), which is twice as much as the BNST. Consequently, we consider that MgO-doped BNST ceramics are able to be a promising candidate in the field of pulsed-power devices.     

Enhanced piezoelectric properties and electrical resistivity in W/Cr co-doped CaBi2Nb2O9 high-temperature piezoelectric ceramics

W/Cr co-doped Aurivillius-type CaBi₂Nb_2-x(W_2/3Cr_1/3)_xO₉ (CBN) (x?=?0.025, 0.050, 0.075, 0.100, and 0.150) piezoelectric ceramics were prepared by the conventional solid-state reaction method. The crystal structure, microstructure, dielectric properties, piezoelectric properties, and electrical conductivity of these ceramics were systematically investigated. After optimum W/Cr modification, the CBN ceramics showed both high d₃₃ and T_C. The ceramic with x?=?0.1 showed a remarkably high d₃₃ value of ~15 pC/N along with a high T_C of ~931?°C. Moreover, the ceramic also showed excellent thermal stability evident from the increase in its planar electromechanical coupling factor k_p from 8.14% at room temperature to 11.04% at 600?°C. After annealing at 900?°C for 2?h, the ceramic showed a d₃₃ value of 14?pC/N. Furthermore, at 600?°C, the ceramic also showed a relatively high resistivity of 4.9?×?10⁵ Ω?cm and a low tanδ of 9%. The results demonstrated the potential of the W/Cr co-doped CBN ceramics for high-temperature applications. We also elucidated the mechanism for the enhanced electrical properties of the ceramics.     

Improved dielectric strength and energy storage density in Ba6−3xLa8+2xTi18O54 (x = 0.5, 2/3, and 0.75) ceramics

Dielectric strength and energy storage density in Ba_6−3xLa_8+2xTi₁₈O₅₄ (x = 0.5, 2/3, and 0.75) ceramics were investigated as functions of composition and microstructure. With increasing x, although the dielectric constant decreased from 113 to 102, the energy storage density increased from 2.3 J/cm³ to 3.2 J/cm³ due to the increased dielectric strength for ceramics prepared by conventional sintering. The energy storage was further improved to 4.2 J/cm³ in ceramics prepared by spark plasma sintering under an electric field of 1058 kV/cm. Both dielectric strength and energy storage density in the present ceramics indicated the strong processing and microstructure dependence. The optimum dielectric strength and energy storage density were achieved in the dense ceramics with fine grains, while both dielectric strength and energy storage density decreased in the ceramics with coarse columnar grains.     

Enhanced energy storage and fast discharge properties of BaTiO3 based ceramics modified by Bi(Mg1/2Zr1/2)O3

Lead-free (1-x)BaTiO₃-xBi(Mg_1/2Zr_1/2)O₃ ((1-x)BT-xBMZ) ceramics with perovskite structure were synthesized by solid-state reaction methods. (1-x)BT-xBMZ solid solution transforms from tetragonal (x≤0.04) to pseudocubic (x≥0.08) and exhibits a dispersive dielectric behavior with respect to frequency, showing typical relaxor characteristics with BMZ increasing. The optimal energy storage density of 1.25 J cm^?3 and energy efficiency of >95% are obtained at x = 0.15, with maximum dielectric breakdown strength of 185 kV cm^-1 at 200 μm thickness., The energy storage density and energy efficiency of 0.85BT-0.15BMZ ceramics maintain at about 0.8 J cm^?3 and 89% at 150 kV cm^-1 over temperature range of 25 °C～150 °C, exhibiting good thermal stability. The pulse discharge capability of 0.85BT-0.15BMZ ceramics were measured under different electric fields, showing a short charge-discharge time of 1.3 μs. Therefore (1-x)BT-xBMZ solid solution with high energy density and efficiency, good temperature stability and fast discharge speed, is promising candidate for high power applications.     

Higher permittivity of Ni-doped lead zirconate titanate,Pb[(Zr0.52Ti0.48)(1-x) Nix]O3, ceramics

The paper reports highest obtained dielectric constant for Ni-doped Lead Zirconate Titanate [PZT, Pb(Zr_0.52Ti_0.48)O₃] ceramics. The Ni-doped PZT ceramic pellets were prepared via conventional solid-state reaction method with Ni content chosen in the range 0–20?at%. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were employed to investigate the crystal structure of the prepared ceramics. The X-ray diffraction analysis indicated that the ceramic pellets had crystallized into tetragonal perovskite structure. A minute displacement of XRD peaks was detected in the diffraction spectra of Ni-doped PZT ceramic samples which when examined by size-strain plot (SSP) method revealed presence of homogenous strain that decreased with increase in concentration of Ni. In FTIR the maximum absorption at 597?cm^?1, 608?cm^?1, 611?cm^?1, 605 and 613?cm^?1 for Ni?=?0, 5, 10, 15 and 20?at%, respectively, confirmed the formation of perovskite structure in all the compositions and the slight shift suggests decrease in cell size on doping. The values of dielectric constant (ε′) & tanδ as a function of frequency and temperature were measured for the prepared ceramics and it revealed highest ever reported dielectric constant for Ni - doped PZT with Ni?=?5?at%. The dielectric variation with temperature exhibited a diffused type ferroelectric–paraelectric phase transition for the doped samples. Also, the maximum dielectric constant value (ε′_max) decreased while the phase transition temperature increased with increase in doping concentration of Ni. The estimated activation energy of different compositions was found to increase from 0.057 to 0.068?eV for x?=?0.00 to x?=?0.20 in ferroelectric phase. The piezoelectric, ferroelectric and magnetic properties were also investigated.     

Effect of Mn-doping on the structure and electrical properties of (Pb0.325Sr0.675)TiO3 ceramics

Pb_0.325Sr_0.675Ti_1-xMn_xO₃ ceramics (x?=?0, 0.001, 0.005, 0.01, and 0.05) were successfully prepared by traditional solid-state reaction method. It was found that the lattice constant calculated through Rietveld refinement initially increased and then decreased with increasing Mn content, which was attributed to the variation in valence state of Mn and Ti ions. The microstructure gradually varied from the coexistence of large grains and fine grains for x?=?0 to the uniform grain for x?=?0.05 by increasing the doping Mn ions. With increasing Mn content from x?=?0 to x?=?0.05, the Curie temperature (Tc) dramatically decreased from 25?°C to ??40?°C and dielectric maximum decreased from 27,100 to 13,200. Pb_0.325Sr_0.675Ti_1-xMn_xO₃ ceramics with x?=?0.001 showed the lowest dielectric loss of 0.006 with a relatively high dielectric peak value of ~ 21,000. The grain boundaries resistance obtained from the complex impedance decreased with the increase of Mn content. The decrease in resistance was ascribed to oxygen vacancies and electronics produced by the change of ionic valence state. X-ray photoemission spectroscopy revealed that Ti ions were Ti⁴⁺ and the valences of Mn ions were deduced to be mainly in the form of Mn²⁺ and/or Mn³⁺ for ceramics with low content of Mn, while the Ti ions were in the form of Ti³⁺ and Ti⁴⁺ and Mn ions were diverse valence states with the coexistence of Mn²⁺, Mn³⁺, and Mn⁴⁺ for ceramics with x?=?0.01 and 0.05.     

High efficiency and power density relaxor ferroelectric Sr0.875Pb0.125TiO3- Bi(Mg0.5Zr0.5)O3 ceramics for pulsed power capacitors

Ferroelectric (1-x)Sr_0.875Pb_0.125TiO₃-xBi(Mg_0.5Zr_0.5)O₃ ((1-x)SPT-xBMZ, x = 0-0.2) ceramics with high discharge efficiency and power density were synthesized via a conventional solid-state sintering method. The prepared (1-x)SPT-xBMZ ceramics were detected as a pure perovskite structure and a dense microstructure, and a typical relaxor behavior and an excellent temperature stability were also observed. Although there is no direct correlation between the degree of diffuseness and the maximum polarization, the high degree of diffuseness can reduce the remanent polarization and significantly improve energy storage and release characteristics of ferroelectric ceramics. Based on a polarization electric-field loop measurement, a recoverable energy storage density of 0.762 J/cm³ and a very high efficiency of 96.34% are achieved when x = 0.2 under 150 kV/cm. The energy storage properties of 0.8SPT-0.2BMZ ceramic exhibit good temperature stability (25−130 °C) and frequency stability (2−80 Hz). In a practical charge-discharge circuit testing, a short discharge pulse-period about 94 ns, a high discharge energy density of 1.7 J/cm³ and an ultra-high-power density of 62.8 MW/cm³ are obtained for the 0.8SPT-0.2BMZ ceramic at 240 kV/cm. The results indicate that the 0.8SPT-0.2BMZ ceramic is a promising dielectric material for high-power pulse capacitors.     

CaTiO3 linear dielectric ceramics with greatly enhanced dielectric strength and energy storage density

CaTiO₃ is a typical linear dielectric material with high dielectric constant, low dielectric loss, and high resistivity, which is expected as a promising candidate for the high energy storage density applications. In the previous work, an energy density of 1.5 J/cm³ was obtained in CaTiO₃ ceramics, where the dielectric strength was only 435 kV/cm. In fact, the intrinsic dielectric strength of CaTiO₃ is predicted as high as 4.2 MV/cm. Therefore, it should be a challenge issue to enhance the dielectric strength and energy storage density of CaTiO₃ ceramics by optimizing the microstructures. In the present work, dense CaTiO₃ ceramics with fine and uniform microstructures are prepared by spark plasma sintering, and the greatly enhanced dielectric strength (910 kV/cm) and energy storage density (6.9 J/cm³) are obtained. This can be ascribed to the improved resistivity and thermal conductivity, associated with the fine and uniform microstructures. The different post‐breakdown features of CaTiO₃ ceramics prepared by different process well interpret why the enhanced dielectric strength is achieved in the SPS sample. The energy storage density can be further improved to 11.8 J/cm³ by introducing the amorphous alumina thin films as the charge blocking layer, where the dielectric strength is 1188 kV/cm.