Enhanced Energy Storage Properties of Ba_0.96Ca_0.04TiO₃ Ceramics Through Doping Bi(Li_1/3Zr_2/3)O₃

Abstract

The (1−x)Ba_0.96Ca_0.04TiO₃−xBi(Li_1/3Zr_2/3)O₃ (x = 0.03–0.15) ceramics were fabricated via the traditional solid reaction method. Characterization results revealed that each component exhibited a pure perovskite structure, and the average grain size significantly diminishes with increasing x. The (1−x)Ba_0.96Ca_0.04TiO₃−xBi(Li_1/3Zr_2/3)O₃ ceramics exhibited prominent relaxor ferroelectric behavior, whose characteristic narrow hysteresis loops effectively enhanced the energy storage performance of the material. Most importantly, the composition with x = 0.10 demonstrated exceptional energy storage properties at 150 kV/cm, achieving a high recoverable energy storage density (W_rec = 1.91 J/cm³) and excellent energy efficiency (η = 90.87%). Under the equivalent electric field, this composition also displayed a superior pulsed discharge performance, including a high current density (871 A/cm²), a high power density (67.3 MW/cm³), an ultrafast discharge time (t_0.9 = 109 ns), and a discharged energy density of 1.47 J/cm³. These results demonstrate that the (1−x)Ba_0.96Ca_0.04TiO₃−xBi(Li_1/3Zr_2/3)O₃ ceramic system establishes a promising design paradigm for the creation and refinement of next-generation dielectrics for pulse power applications.

1. Introduction

Nowadays, energy storage materials have been receiving extensive attention in pulsed power components derived from their high storage density, wide application temperature range and ultra-fast charging–discharging [1,2,3]. Currently, lead zirconate titanate (PZT) remains the dominant commercial ceramic material. While lead-based ceramics exhibit excellent performance, the presence of PbO₂ poses significant risks to human health and can lead to environmental pollution. Therefore, the development of high-performance, lead-free ceramic materials has become a critical focus for pulsed power capacitor research. Furthermore, lead-free ceramics generally exhibit lower densities (<5.5 g/cm³) compared to lead-based ceramics (density ~7.5 g/cm³). Achieving equivalent energy storage densities with lighter materials is highly desirable for pulsed power devices [4]. This demand for light-weighting further promotes the development of lead-free systems such as (Na,K)NbO₃ (KNN), Bi₀.₅Na₀.₅TiO₃ (BNT), and BaTiO₃ (BT) [5]. Despite their potential, KNN and BNT ceramics suffer from limitations such as micro-cracking and defect formation during processing or under high electric field cycling, which can compromise their average lifetime, breakdown strength, and overall stability. These challenges hinder their effective integration into high-efficiency pulsed power systems. In contrast, BT-based ceramics exhibit high energy storage density, excellent temperature stability, and long cycle life, making them more suitable for emerging pulsed power capacitor applications that demand high power, miniaturization, and lightweight characteristics [6]. Importantly, BT-based ceramics offer high safety as energy storage components and enable rapid frequency response adjustments, which are critical for ensuring the reliable and efficient operation of pulsed power systems. However, the rapid polarization decay in pure BaTiO₃ ceramics, which is triggered by the switching and domain wall vibrations of its large ferroelectric domains under an external electric field, fundamentally limits its suitability for achieving the energy storage characteristics necessary for pulse power devices [7]. The substitution of Ca²⁺ ions into the BaTiO₃ (BT) structure to create the Ba_1−xCa_xTiO₃ (BCT) system is a well-established strategy for optimizing energy storage capabilities. By promoting cation disorder, this approach effectively disrupts the long-range crystallographic order, which in turn leads to a significant decrease in the average ferroelectric domain size. The resulting structural changes give rise to enhanced relaxor properties and a diminished remnant polarization, validating this method as a highly effective means of boosting energy storage performance [8]. The energy storage density (W_rec) of BCT-based ceramic is calculated by the following formula [9].

$$\mathrm{W}={\int }_0^{{\mathrm{P}}_{\mathrm{m}\mathrm{a}\mathrm{x}}}\mathrm{E}\mathrm{d}\mathrm{P}$$

(1)

$${\mathrm{W}}_{\mathrm{rec}}={\int }_{{\mathrm{P}}_{\mathrm{r}}}^{{\mathrm{P}}_{\mathrm{m}\mathrm{a}\mathrm{x}}}\mathrm{E}\mathrm{d}\mathrm{P}$$

(2)

$$\eta ={\displaystyle \frac{W_{rec}}{W}}\times 100\%$$

(3)

where W, W_rec, E, P_r, P_max, and $\eta$ represent total stored energy density, recoverable energy storage density, applied electric field, remnant polarization, maximum polarization, and energy storage efficiency, respectively. However, the BCT system with low energy density (~0.2 J/cm³) and energy efficiencies ($\eta$~58%) cannot meet the requirements in real application [10]. In recent years, it was found that the Bi³⁺-based with the high P_max and low P_r optimized BT-based ceramics, which possessed large W_rec [11,12,13]. Therefore, the BCT-BiMeO₃ systems have been researched gradually. The (1−x)Ba_0.8Ca_0.2TiO₃−xBi(Mg_0.5Ti_0.5)O₃ ferroelectric ceramics possess near-plateau relative dielectric constant in a broad temperature range and are regarded as potential candidate materials in the field of energy storage [14,15]. Moreover, 0.5Ba_0.8Ca_0.2TiO₃-0.5Bi(Mg_0.5Ti_0.5)O₃-BiFeO₃ ceramics exhibited a high energy density (~0.58 J/cm³) and efficiencies (~82%) at 100 kV/cm [16]. Therefore, the BCT-BiMeO₃ ceramic system is considered a promising candidate for achieving enhanced energy storage performance.

In this work, a series of (1−x)BCT−xBLZ ceramics were successfully synthesized through the conventional solid-phase sintering process to systematically evaluate the impact of BLZ substitution on phase composition, microstructure, dielectric performance, and energy storage characteristics. Significantly, the ceramic system was found to exhibit exceptional energy storage characteristics, validating its promise as a viable material for advanced pulse power energy storage capacitor applications.

2. Experimental

2.1. Materials and Methods

The (1−x)Ba_0.96Ca_0.04TiO₃−xBi(Li_1/3Zr_2/3)O₃ (abbreviated as (1−x)BCT−xBLZ, x = 0.03–0.15) ceramics were fabricated via the solid-phase sintering process. Stoichiometric amounts of raw powders, including BaCO₃ (99.0%), CaCO₃ (99.0%), MgO (99.7%), TiO₂ (99%), Li₂CO₃ (99%), ZrO₂ (99.8%), and Bi₂O₃ (99%), were measured as the starting materials. All the raw materials were sourced from Sinopharm Group Chemical Reagent Co., Ltd. (Shanghai, China). To ensure optimal mixing and homogenization, the powders were initially subjected to planetary ball milling at 1200 rpm for 12 h, using anhydrous ethanol as the dispersion medium. This controlled milling process facilitated the intimate contact of the constituent powders. The resulting slurry was carefully dried at 100 °C for 6 h to remove the ethanol, and the dried powder was subsequently ground and sieved through a 120-mesh screen to obtain a pre-treated powder with controlled particle size. This pre-treated powder was then calcined in a muffle furnace at 1000 °C for 4 h to promote the solid-state reaction and the formation of the desired primary crystalline phase. Following calcination, the resulting bulk material was ground and sieved through a 120-mesh screen. To achieve fine and homogeneous particles, the calcined powders underwent ball-milling for 10 h. The resulting slurry from this secondary milling process was treated identically to the first (drying at 100 °C for 6 h, grinding, and sieving through a 120-mesh screen), yielding a fine and uniformly sized calcined powder with optimized characteristics. Subsequently, this powder was thoroughly mixed with an 8 wt.% aqueous solution of polyvinyl alcohol (PVA), which served as a binder to facilitate green body formation. The mixture was then ground and passed through an 80-mesh sieve to ensure uniform binder distribution. Following granulation, the mixture was uniaxially pressed at 150 MPa into disk-shaped green compacts with approximate dimensions of 12 mm in diameter and 1 mm in thickness. A burnout process was performed by heating the pellets at 550 °C for 2 h. The final densification was achieved by sintering the pellets in an air atmosphere at 1480 °C for 2 h, yielding the dense ceramic samples.

2.2. Characterization Techniques

The phase composition of the BCT-xBLZ ceramics was measured by X-ray diffraction system (Rigaku D/max-2500/PC, Cu Kα₁, λ = 1.5406 Å, Tokyo, Japan). For microstructural analysis, the samples were thermally etched at 1150 °C for 2 h, and their surface morphologies were subsequently examined by a scanning electron microscope (SEM; HITACHI S-4300, Tokyo, Japan). Bulk densities were measured for all samples via the Archimedes method. To facilitate electrical measurements, the sintered ceramic disks were polished to obtain smooth and parallel surfaces. Silver paste was then applied to both faces and fired at 650 °C for 30 min in an air atmosphere to form electrodes. The dielectric performance was characterized through the precision impedance analyzer (4294 Agilent Inc., Bayan Lepas, Malaysia). The static storage performance was evaluated by measuring the polarization-electric field (P-E) curves at 1 Hz with the ferroelectric test system (Precision Premier II, Radiant Technologies Inc., Albuquerque, NM, USA). Furthermore, the dynamic charge–discharge characteristics were investigated through a dielectric charge–discharge test platform (CD-003, TG Technology, Shenzhen, China).

3. Results and Discussion

Figure 1a schematically illustrates the fabrication process employed for the ceramics. Based on this synthesis route, the surface images of the (1−x)BCT−xBLZ ceramics with x ranging from 0.03 to 0.15 are presented in Figure 1b–g. All compositions are characterized by a uniform grain structure and high densification. The average grain size and relative density for each composition are compiled in Figure 1h. Specifically, the average grain sizes were measured to be 7.78 μm, 5.78 μm, 4.7 μm, 2.3 μm, 1.65 μm, and 1.25 μm for the respective compositions, revealing a systematic decrease as the dopant concentration x increases. This trend of grain refinement is consistent with the solute drag effect, where dopant ions pin grain boundaries. When the host Ti⁴⁺ ions are substituted by the larger-sized (Li_1/3Zr_2/3)³⁺, a significant lattice strain energy (ΔGstrain) is induced. This energy barrier to grain boundary motion is described by the equation [10]:

$$∆{\mathrm{G}}_{\mathrm{s}\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{i}\mathrm{n}}=4\mathsf{\pi }{\mathrm{N}}_{\mathrm{A}}\left[{\displaystyle \frac{{\mathrm{r}}_0}{{2({\mathrm{r}}_{\mathrm{d}}-{\mathrm{r}}_0)}^2}}+{\displaystyle \frac{1}{3}}{({\mathrm{r}}_{\mathrm{d}}-{\mathrm{r}}_0)}^3\right]$$

(4)

where r₀, r_d, N_A, and M represent the optimal radius of the lattice site, the ionic radius of the dopant, Avogadro’s constant, and Young’s modulus, respectively. The substitution of host Ti⁴⁺ ions by the larger-sized (Li_1/3Zr_2/3)³⁺ ions results in a significant increase in ΔGstrain. This strain energy creates a drag force that impedes the migration of grain boundaries, thereby suppressing grain growth. The relative densities of the samples were calculated based on the experimentally determined bulk densities of each composition, which were 5.27, 5.48, 5.54, 5.84, 5.69, and 5.64 g/cm³. The trend in relative density as a function of composition is shown in Figure 1h. The initial improvement in density up to 89.7% (x = 0) is advantageous for electrical performance, as a denser microstructure typically possesses fewer defects and thus a higher breakdown strength. The subsequent decrease in density to 94.3% at higher dopant levels (x = 0.15) may be attributed to internal strains generated by modifications to the domain structure and mobility [17]. The elemental distribution images of x = 0.10 ceramics are shown in Figure 2. All elements (Ba, Ti, Ca, Bi, Li, O, and Zr) are uniformly distributed in the ceramics, which indicates good chemical homogeneity. In addition, such uniform element distributions and dense microstructure are beneficial to obtain high energy storage properties.

The crystal structure of the (1−x)BCT−xBLZ ceramics was investigated by XRD, with the resulting patterns presented in Figure 3a. Analysis of XRD indicated a pure ABO₃-type perovskite phase for all compositions. The absence of secondary peaks confirms that the BLZ dopant entered the BaTiO₃ lattice to form a complete solid solution. To ascertain the ionic occupancy within the perovskite ABO₃ lattice, an analysis of ionic radii was performed. The effective ionic radius of the complex B-site cation, (Li₁/₃Zr₂/₃)³⁺, was estimated to be 0.733 Å via a weighted average of its components (R_(Li⁺₎ = 0.76 Å; R_(Zr⁴⁺₎ = 0.72 Å [11]). This value is reasonably close to that of the native B-site cation Ti⁴⁺ (0.605 Å). The Bi³⁺ cation, with a much larger radius of 1.11 Å, is sterically hindered from occupying the B-site and is thus expected to substitute for Ba²⁺ (1.61 Å) at the A-site. Consequently, the structural model assumes Bi³⁺ occupies the A-site and (Li₁/₃Zr₂/₃)³⁺ occupies the B-site. As shown in the magnified XRD patterns in Figure 4b, the main diffraction peak exhibits a systematic shift towards lower 2θ angles with the addition of x. According to Bragg’s law, this shift signifies an expansion of the unit cell volume. This lattice expansion is consistent with previous reports on similar perovskite systems, such as BaTiO₃-Bi(Li_0.5Nb_0.5)O₃ and (Bi_0.5Na_0.5)TiO₃-BaTiO₃-Bi(Li_0.5Ta_0.5)O₃ ceramics [18,19]. In order to gain a deeper understanding of the phase structure characteristics of the materials, a systematic Rietveld refinement analysis was performed on a series of samples using the FullProf studio software package, as shown in Figure 5. The fit parameter (χ²) of all samples is below 8, indicating the reliability of the Rietveld refinement procedure. Quantitative analysis of the phase composition as a function of doping concentration revealed that the cubic perovskite phase (Pm3m) was dominant at x = 0.03. The samples with 0.05 ≤ x ≤ 0.12 depict the coexistence of a tetragonal (P4mm) phase and pseudo-cubic phase (Pm3m). At x = 0.10, the content of the cubic (Pm3m) and tetragonal (P4mm) phases was 26.85% and 73.15%, respectively. At x = 0.15, the material exhibited a tetragonal phase. Detailed Rietveld refinement lattice parameters, agreement factors, and cell volume for the (1−x)BTC−xBLZ ceramics with varying x content are listed in

Table 1. Rietveld refined structural parameters along with lattice parameter and cell volume for BaTCx ceramics with different x content.

Sample	Lattice Parameters (Å)			Volume (Å3)	Theoretical Densities (g/cm3)	C Phase (%)	T Phase (%)	R Factors (%)
x	a	b	c					Rwp	Rp	χ2
0.03	4.0106	4.0106	4.0106	64.35	6.002	93.76	6.34	6.34	5.79	5.35
0.05	4.0078	4.0078	4.0078	64.43	5.997	82.33	17.67	5.62	6.21	4.91
0.07	4.0041	4.0041	4.0041	64.51	5.994	63.74	36.26	6.71	5.94	6.12
0.10	4.0012	4.0012	4.0218	64.58	5.989	26.85	73.15	5.86	5.76	4.76
0.12	3.9991	3.9991	4.0249	64.63	5.986	14.34	85.66	6.27	5.69	6.97
0.15	3.9989	3.9989	4.0301	64.68	5.983	4.75	95.25	5.41	6.17	5.46

. With increasing x content, the significant difference between the lattice parameters a and c indicates the tetragonal crystal symmetry of the samples, and that the cell volume gradually increased.

Figure 5 shows the temperature dependence of the dielectric permittivity for the (1−x)BCT−xBLZ ceramics at various frequencies. All samples exhibit a single dielectric peak, the magnitude of which decreases slightly with increasing frequency. This behavior is characteristic of frequency dispersion, arising from the inability of the electric dipoles within the matrix to reorient in phase with the applied electric field at higher frequencies. A significant trend observed is the progressive broadening of the dielectric peak with x increasing, which indicates an enhancement in the relaxor characteristics. This is attributed to dopant-induced local lattice distortions, which create random electric fields and lead to the formation of polar nano regions (PNRs) [20]. At any given frequency, the peak permittivity is also suppressed with increasing BLZ content, a phenomenon linked to the increased ionic disorder and charge fluctuations that cause compositional inhomogeneity within the lattice. With the addition of x, the Curie temperature of the sample gradually decreases. This is mainly due to the difference in donor–acceptor atomic ratio and the difference in valency, which produces a different concentration of oxygen vacancy. Additionally, the pinning effect of oxygen vacancy on ferroelectric domain makes it difficult to move, thus reducing the temperature from ferroelectric to paraelectric phase [21]. Furthermore, the hump observed in the dielectric loss profile diminishes as the test frequency increases, which provides further evidence for the enhanced relaxation properties of the samples. Notably, all compositions exhibited a low dielectric loss (tanδ < 0.1), a crucial attribute for achieving a high dielectric breakdown strength.

To further investigate the relaxation performance, a modified Curie–Weiss law can be employed: 1/ɛ − 1/ɛ_m = (T − T_m)^γ /C (T > T_m), where γ, εm, and C represent the exponent that describes the degree of relaxation, the maximum permittivity at temperature T_m, and the Curie-like constant, respectively. The values of γ are 1.24, 1.41, 1.54, 1.78, 1.85, and 1.96 for the samples with x = 0.03–0.15, respectively, as shown in Figure 6. Incorporating BLZ introduces aliovalent ions and an ionic size mismatch into the host lattice, which serves to break down the long-range ordered ferroelectric domains. This process promotes the nucleation of finer nanodomains, a structural evolution that is crucial for enhancing the energy storage performance.

Weibull distribution is a better means to further evaluate the value of BDS. The BDS characteristic of the (1−x)BCT−xBLZ ceramics can be defined as follows [8,22]:

$$\mathrm{P}=1-{\mathrm{e}}^{{-({\displaystyle \frac{\mathrm{E}}{\mathsf{\alpha }}})}^{\mathsf{\beta }}}$$

(5)

where P, E, $\mathsf{\alpha }$, and $\mathsf{\beta }$, represent the electric failure possibility, the breakdown strength, characteristic breakdown strength (typically, the breakdown strength at the 63.2% occurrent possibility of failure), the deviation of experimental data, respectively. The Weibull distribution of the breakdown strength (BDS) for all compositions is plotted in Figure 7a. The shape parameter (β) varies with composition, reaching a peak value of 15.6 for x = 0.10. These high β values indicate a low scatter and high reliability in the collected data. Furthermore, the coefficients of determination (R²) obtained from the Weibull analysis were found to be 0.92, 0.91, 0.86, 0.95, 0.89, and 0.97 for the respective compositions, providing further support for the robustness of the experimental data. As presented by the characteristic breakdown strength in Figure 7b, the BDS progressively improves from 207 kV/cm for x = 0.03 to a maximum value of 319 kV/cm at x = 0.10. This enhancement is intimately linked to the observed reduction in grain size. It is well established that grain boundaries have a substantially higher electrical resistivity than the grain interiors [23]. Consequently, grain refinement leads to a significant increase in the density of grain boundaries per unit volume, creating a more extensive network of high-resistivity regions. These resistive grain boundaries act as effective barriers that impede the migration of charge carriers, thereby markedly reducing the material of leakage current. This suppression of leakage current is a critical factor in achieving a superior dielectric breakdown strength.

Figure 8a shows P-E curves of the (1−x)BCT−xBLZ (x = 0.03–0.15) ceramics at 150 kV/cm. The increasing width of the P-E loops at higher field strengths points to a hindered back-switching of polar nano domains (PNRs), a process that requires a greater electric field to actuate during loading and unloading. All samples exhibit quasi-rectangular single P-E hysteresis loops. With increasing applied field amplitude, the loops systematically broaden, signifying greater energy dissipation during the polarization reversal cycle. This increased hysteresis loss is ascribed to the field-dependent dynamics of nanodomain switching. At higher electric fields, domain walls more readily overcome pinning barriers, but their motion and reorientation result in more significant energy dissipation, leading to the observed widening of the P-E loop. Meanwhile, with increasing x, the P_max decrease from 30.8 μC/cm² (x = 0) to 15.7 μC/cm² (x = 0.15) is mainly caused by the electrically induced short-range ordered relaxation nanodomains returning to long-range disordered ferroelectric domains after the removal of the electric field [24]. The W_rec and ƞ as a function of BLZ are shown in Figure 8b. The W_rec remarkably increases from 1.38 J/cm³ (x = 0.03) to the maximum value of 1.91 J/cm³ (x = 0.10), and then decreases to 1.13 J/cm³ (x = 0.15). It is attributed that Li⁺ and Zr⁴⁺ at the B-position in the body-centered position of the crystal will reduce the distance between the B-position and oxygen ions, which greatly affects the conduction behavior of electrons in the ceramic, resulting in increasing storage density. Meanwhile, the η of the samples increases from 58.95% (x = 0.03) to the maximum value of 90.87% (x = 0.15), which suggests that Bi³⁺-Bi³⁺ ion pairs are formed by the introduction of Bi ions at the A position. The 6p orbital of Bi³⁺-Bi³⁺ ion pairs and the 2p orbital of O²⁻ ion are hybridized, which leads to the thinning of the hysteresis loop, thus obtaining higher energy storage efficiency [25,26]. For performance evaluation, the energy storage density and efficiency, along with corresponding electric field of the (1−x)BCT−xBLZ ceramics, are benchmarked against other lead-free materials in

Table 2. Benchmarking the energy storage performance of the (1−x)BCT−xBLZ ceramics.

Composition	W (J/cm3)	η (%)	E (kV/cm)	References
BCT-BLZ	1.91	90.87%	150	This work
BT-based	1.5	91.7%	160	[27]
BNT-BT	1.26	84.3%	120	[28]
BT-based high entropy	1.57	72%	170	[29]
BF-BT	1.27	95.4%	185	[30]
BT-ST	0.59	95.5%	120	[31]
0.85BT-0.15BMZ	0.8	89%	150	[32]
BST	1.76	77.6%	120	[33]
BBTS	1.52	72.3%	100	[34]

BT: BaTiO₃; (Ba_0.70Ca_0.30)TiO₃: BCT; BNT-BT: Na_0.5Bi_0.5TiO₃-BaTiO₃; BF-BT: BiFeO₃-BaTiO₃; BT-ST: BaTiO₃-BaSrO₃; 0.85BT-0.15BMZ: 0.85BaTiO₃-0.15Bi(Mg_1/2Zr_1/2)O₃; BST:Ba_1−xSm_xTiO₃; BBTS: (Ba_0.775Bi_0.15)Ti_0.8Sn_0.2O_3.

. It is evident from this comparison that the present ceramic system shows a superior energy storage capability, a distinction that is particularly noteworthy given that it is achieved at a low electric field.

The impulse power system has the advantage of instantaneous discharge in practical application. Therefore, investigating the pulse charge–discharge characteristics of energy storage ceramics is of significant practical importance. The discharge energy density (W_dis) at x = 0.10 can be evaluated by the following formula:

$$C_D={\displaystyle \frac{I_{max}}{S}}$$

(6)

$$P_D={\displaystyle \frac{E\times I_{max}}{2S}}$$

(7)

$$W_{dis}={\displaystyle \frac{R\int I^2\left(t\right)dt}{V}}$$

(8)

where C_D, P_D, W_d, I_max, E, S, R, and V are the discharge current, power density, discharge energy storage, maximum current, electric field, electrode area, load resistance (200 Ω), and sample volume, respectively. Figure 9a displays the underdamped pulse discharge profiles under various applied electric fields. It is observed that while the fundamental waveform shape remains consistent, the peak current (I_max) increases substantially from 10.3 A to 57.8 A as the electric field rises from 30 kV/cm to 150 kV/cm. The corresponding W_dis with the applied electric field is presented in Figure 9b. The W_dis exhibits a monotonic increase with the field strength, reaching a maximum value of approximately 1.47 J/cm³ at the highest tested field of 150 kV/cm, with a relatively long discharge time (t_0.9) of 109 ns. Notably, the maximum discharged energy density (W_dis = 1.47 J/cm³) obtained from the pulse test is lower than the recoverable energy storage density (W_rec = 1.91 J/cm³) calculated from the P-E loop. This discrepancy is primarily attributed to energy dissipation within the system, which includes losses from the equivalent series resistance (ESR) of the charge–discharge circuit and increased energy dissipation due to the viscous drag on domain walls during their rapid motion. Furthermore, the load resistor in a practical application introduces an additional pathway for energy loss. Therefore, while W_rec represents an idealized storage capacity, W_dis provides a more practical measure of the effective discharged energy density relevant to real-world applications. Figure 9c shows the overdamped pulse discharge profiles for the same composition (x = 0.10), which exhibit similar discharge behaviors where the peak current grows with the applied field. From these measurements, the current density (C_D) and power density (P_D) were calculated and are plotted against the electric field in Figure 9d. Both C_D and P_D increase progressively with the field strength, attaining impressive maximum values of 871 A/cm² and 67.3 MW/cm³, respectively, at 150 kV/cm. This high performance is enabled by the material’s high polarization and rapid energy release. These excellent charge–discharge characteristics affirm the significant potential of the 0.9BCT-0.1BLZ ceramic for pulse power capacitor applications.

4. Conclusions

The (1−x)Ba_0.96Ca_0.04TiO₃−xBi(Li_1/3Zr_2/3)O₃ (x = 0.03–0.15) lead-free ceramics were synthesized by conventional solid-state method. All compositions crystallized into a pure perovskite structure, and the average grain size systematically decreased with increasing Bi(Li_1/3Zr_2/3)O₃ dopant concentration. The composition with x = 0.10 exhibited prominent energy storage performance, achieving a high energy storage density of 1.91 J/cm³ and an excellent efficiency of 88.89% at 150 kV/cm. Furthermore, pulse discharge tests conducted at the same electric field demonstrated superior power characteristics for this composition, with C_D and P_D values reaching maximum values of 871 A/cm² and 67.3 MW/cm³, respectively. Concurrently, it delivered a maximum discharged energy density of 1.47 J/cm³ within a rapid discharge time. These results underscore the broad application prospects of (1−x)Ba_0.96Ca_0.04TiO₃−xBi(Li_1/3Zr_2/3)O₃ ceramics for pulsed capacitor technologies.