Enhancing giant dielectric properties of Ta5+-doped Na1/2Y1/2Cu3Ti4O12 ceramics by engineering grain and grain boundary

Various strategies to improve the dielectric properties of ACu₃Ti₄O₁₂ (A = Sr, Ca, Ba, Cd, and Na_1/2Bi_1/2) ceramics have widely been investigated. However, the reduction in the loss tangent (tanδ) is usually accompanied by the decreased dielectric permittivity (ε′), or vice versa. Herein, we report a route to considerably increase ε′ with a simultaneous reduction in tanδ in Ta⁵⁺–doped Na_1/2Y_1/2Cu₃Ti₄O₁₂ (NYCTO) ceramics. Dense microstructures with segregation of Cu– and Ta–rich phases along the grain boundaries (GBs) and slightly increased mean grain size were observed. The samples prepared via solid-state reaction displayed an increase in ε′ by more than a factor of 3, whereas tanδ was significantly reduced by an order of magnitude. The GB–conduction activation energy and resistance raised due to the segregation of Cu/Ta–rich phases along the GBs, resulting in a decreased tanδ. Concurrently, the grain–conduction activation energy and grain resistance of the NYCTO ceramics were reduced by Ta⁵⁺ doping ions owing to the increased Cu⁺/Cu²⁺, Cu³⁺/Cu²⁺, and Ti³⁺/Ti⁴⁺ ratios, resulting in enhanced interfacial polarization and ε′. The effects of Ta⁵⁺ dopant on the giant dielectric response and electrical properties of the grain and GBs were described based on the Maxwell–Wagner polarization at the insulating GB interface, following the internal barrier layer capacitor model.     

High dielectric permittivity and dielectric relaxation behavior in a Y2/3Cu3Ti4O12 ceramic prepared by a modified Sol−Gel route

In this work, Y_2/3Cu₃Ti₄O₁₂ ceramics were fabricated via a modified sol?gel route. Structural, dielectric, and electrical parameters were systematically investigated. The XRD results indicate that a CaCu₃Ti₄O₁₂ phase (JCPDS No. 75–2188) is present in every sintered sample. SEM images of Y_2/3Cu₃Ti₄O₁₂ ceramics disclose a fine-grained ceramic microstructure. Interestingly, high dielectric permittivity, ～6600–7600, with loss tangents of ～0.918–1.086 were achieved in the sintered Y_2/3Cu₃Ti₄O₁₂ samples. Density functional theory (DFT) calculations were used to investigate the most stable structure of the Y_2/3Cu₃Ti₄O₁₂ ceramics. Our DFT results reveal that two calcium vacancies (V_Ca) are isolated from each other. We also determined the lowest energy configuration of an oxygen vacancy (V_O) in the Y_2/3Cu₃Ti₄O₁₂ ceramics occurred during the sintering process. We found that the V_O is trapped close to the Y atom in this structure. Both computational and experimental studies specify that the oxygen vacancy is located close to the Y atom in the Y_2/3Cu₃Ti₄O₁₂ lattice and it might be a bivalent oxygen vacancy. As a result, due to charge balance, charge compensation of the transition ions, i.e., Cu and Ti ions, might take place. The charge compensation mechanisms in the Y_2/3Cu₃Ti₄O₁₂ lattice were verified using an XPS technique. Impedance spectroscopy confirms the presence of an inhomogeneous microstructure consisting of semiconducting grains and insulating grain boundaries in the sintered Y_2/3Cu₃Ti₄O₁₂ ceramics. This electrical result is consistent with the computational analysis, showing that a charge compensation mechanism might be involved in generation of the grains' semiconductive region due to the presence of a V_O. Consequently, high dielectric permittivity in Y_2/3Cu₃Ti₄O₁₂ may have originated from an internal barrier layer capacitor (IBLC) effect.     

Preparation,characterization, and giant dielectric permittivity of (Y3+ and Nb5+) co–doped TiO2 ceramics

The microstructure and giant dielectric properties of Y³⁺ and Nb⁵⁺ co–doped TiO₂ ceramics prepared via a chemical combustion method are investigated. A main rutile–TiO₂ phase and dense ceramic microstructure are obtained in (Y_0.5Nb_0.5)_xTi_1-xO₂ (x = 0.025 and 0.05) ceramics. Nb dopant ions are homogeneously dispersed in the microstructure, while a second phase of Y₂O₃ particles is detected. The existence of Y³⁺, Nb⁵⁺, Ti⁴⁺ and Ti³⁺ as well as oxygen vacancies is confirmed by X–ray photoelectron spectroscopy and X–ray absorption near edge structure analysis. The sintered ceramics exhibit very high dielectric permittivity values of 10⁴–10⁵ in the frequency range of 40–10⁶ Hz. A low loss tangent value of ≈0.08 is obtained at 40 Hz. (Y_0.5Nb_0.5)_xTi_1-xO₂ ceramics can exhibit non–Ohmic behavior. Using impedance spectroscopy analysis, the giant dielectric properties of (Y_0.5Nb_0.5)_xTi_1-xO₂ ceramics are confirmed to be primarily caused by interfacial polarization.     

Microstructural evolution,non‐Ohmic properties,and giant dielectric response in CaCu3Ti4−xGexO12 ceramics

The microstructural evolution, non‐Ohmic properties, and giant dielectric properties of CaCu₃Ti_4?xGe_xO₁₂ ceramics (x=0‐0.10) are systematically investigated. The Rietveld refinement confirms the existence of a pure CaCu₃Ti₄O₁₂ phase in all samples. Significantly enlarged grain sizes of CaCu₃Ti_4?xGe_xO₁₂ ceramics are associated with the liquid phase sintering mechanism. Enhanced dielectric permittivity from 6.90×10⁴ to 1.08×10⁵ can be achieved by increasing Ge⁴⁺ dopant from x=0‐0.10, whereas the loss tangent is remarkably reduced by a factor of ≈10. Non‐Ohmic properties are enhanced by Ge⁴⁺ doping ions. Using impedance and admittance spectroscopies, the underlying mechanisms for the dielectric and nonlinear properties are well described. The improved nonlinear properties and reduced loss tangent are attributed to the enhanced resistance and conduction activation energy of the grain boundaries. The largely enhanced permittivity is closely associated with the enlarged grain sizes and the increase in the Cu⁺/Cu²⁺ and Ti³⁺/Ti⁴⁺ ratios, which are calculated from the X‐ray absorption near‐edge structure.     

The Lowered Dielectric Loss and Grain‐Boundary Effects in La‐doped Y2/3Cu3Ti4O12 Ceramics

The effects of La concentration on the electrical conductivity and electric modulus of Y_2/3?xLa_xCu₃Ti₄O₁₂ ceramics (0.00 ≦ x ≦ 0.20) were investigated in detail. Proper amount of La substitution in Y_2/3?xLa_xCu₃Ti₄O₁₂ ceramics made the dielectric loss decreased. When x = 0.10, Y_2/3?0.10La_0.10Cu₃Ti₄O₁₂ ceramics exhibited the highest grain‐boundary resistance (0.893 MΩ) and the lowest dielectric loss (about 0.025 at 1 kHz), meanwhile the samples exhibited a relatively high dielectric constant above 6000 over a wide frequency range from 40 Hz to 1 MHz. The decreased dielectric loss was attributed to the enhanced grain‐boundary resistance. With the increase in La concentration, the dielectric relaxation behaviors correlated with the grain‐boundary effects were significantly enhanced. By La doping, the activation energies for the conduction in grain boundaries were slightly depressed, and the activation energies for the relaxation process in grain boundaries were slightly changed. Based on the activation values, it can be concluded that the doubly ionized oxygen vacancies had substantial contribution to the conduction and relaxation behaviors in grain boundaries.     

Phase Formation and Enhanced Dielectric Response of Y2/3Cu3Ti4O12 Ceramics Derived from the Sol–Gel Process

Y_2/3Cu₃Ti₄O₁₂ (YCTO) ceramics were successfully synthesized by sol–gel method (SG) and solid‐state method (SS), respectively. The optimized processing parameters for the syntheses of precursor powders by sol–gel process were determined as follows: the Ti(OC₄H₉)₄ concentration was 0.50 mol/L, the CH₃COOH volume was 8 mL, and the volume percentage of H₂O was 11.2%. Particularly, on the basis of XRD and TG‐DSC analyses, the phase formation temperature of YCTO‐SG was at least 100°C lower than that of YCTO‐SS. YCTO‐SG ceramics sintered at 1060°C for 25 h showed fine‐grained microstructure, and higher dielectric constant (ε′ ≈ 5.24 × 10⁴) at 1 kHz compared to YCTO‐SS ceramics (ε′ ≈ 0.93 × 10⁴). The higher dielectric constant of the YCTO‐SG ceramics was attributed to the grain size effect. Furthermore, the YCTO‐SG ceramics showed a distinct high‐temperature (>300°C) relaxor‐like behavior. According to the calculated activation energy value, the single ionization of oxygen vacancies was responsible for the conduction and dielectric anomaly behaviors of YCTO‐SG ceramics.     

Giant dielectric response and grain heterogeneity of Y2/3Cu3Ti4O12–TiO2 composite ceramics fabricated by hydrothermal process

Due to the boom of the electronic information industry, dielectric ceramic materials are widely applied in passive components such as multilayer ceramic capacitors. In this article, Y_2/3Cu₃Ti₄O₁₂–TiO₂ composite ceramics with outstanding dielectric properties (ε_r = 2.29 × 10⁶ at 20 Hz, ε_r = 4.49×10⁵ at 1 kHz) were successfully prepared by hydrothermal and in situ solid-state methods. The minimum dielectric loss value (at 1 kHz) of the obtained composite ceramics is about 0.57. The experimental results show that Y_2/3Cu₃Ti₄O₁₂ has a composite perovskite structure with cation vacancies, which causes internal electron-pinned defect-dipole, and the easy entry of excessive titanium ions to produce donor defects. Meanwhile, the heterogeneous grains with a pomegranate-like microstructure were observed in the prepared composite ceramics, and interfacial polarization between subgrain boundaries was substantiated by impedance analysis. The abundant weakly trapped electrons and more polarized interfaces formed by grain and subgrain boundaries are the primary sources of the excellent dielectric properties of composite ceramics.     

Enhanced intrinsic permittivity and bulk response in Y2/3Cu3Ti4+xO12 ceramics

Considering the contribution of the mixed valence structure of Ti³⁺ and Ti⁴⁺ to the semiconductivity of grain, compositions with the formula of Y_2/3Cu₃Ti_4+xO₁₂ were designed and prepared. The dielectric bulk responses of Y_2/3Cu₃Ti_4+xO₁₂ ceramics were explored in detail. Changing Ti stoichiometry gives rise to an increase of the intrinsic permittivity. Y_2/3Cu₃Ti_3.925O₁₂ ceramic exhibits a higher intrinsic permittivity of ~120 at 60 MHz than that of pure Y_2/3Cu₃Ti₄O₁₂ ceramics (87 at 60 MHz). Additionally, the activation energies of bulk responses are significantly enhanced by changing Ti stoichiometry, which is closely linked with the increase of Ti³⁺/Ti⁴⁺.     

Relaxor‐like behaviors in Na1/2Bi1/2Cu3Ti4O12 ceramics

Dielectric properties of Na_1/2Bi_1/2Cu₃Ti₄O₁₂ ceramics were evaluated over the temperature range 300‐720 K. Two relaxor‐like dielectric anomalies were found. The low‐temperature anomaly was confirmed to be an oxygen‐vacancy‐related relaxation process. It is a pseudo‐relaxor behavior caused by a bulk relaxation and a Maxwell‐Wagner relaxation. The high‐temperature one was evidenced to be an electric ferroelectric phase‐transition process resulting from the oxygen‐vacancy ordering.     

Improved dielectric properties and grain boundary response of SrTiO3 doped Y2/3Cu3Ti4O12 ceramics fabricated by Sol-gel process for high-energy-density storage applications

A chemical solution processing method based on sol-gel chemistry (SG) was used to synthesize (1-x)Y_2/3Cu₃Ti₄O₁₂-xSrTiO₃ (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) ceramics successfully. The 0.85Y_2/3Cu₃Ti₄O₁₂-0.15SrTiO₃ ceramics sintered at 1050 °C for 20 h showed fine-grained microstructure and high dielectric constant (ε′ ≈ 1.7 × 10⁵) at 1 kHz. Furthermore, the 0.85Y_2/3Cu₃Ti₄O₁₂-0.15SrTiO₃ ceramics appeared distinct pseudo-relaxor behavior. Two electrical responses were observed in the combined modulus and impedance plots, indicating the presence of Maxwell-Wagner relaxation. Sr vacancies and additional oxygen vacancies had substantial contribution to the sintering behavior, an increase in grain growth, and relaxation behaviors in grain boundaries. The contributions of semiconducting grains with the nanodomain and insulating grain boundaries (corresponding to high-frequency and low-frequency electrical response, respectively) played important roles in the dielectric properties of (1-x)Y_2/3Cu₃Ti₄O₁₂-xSrTiO₃ ceramics. The occurrence of the polarization mechanism transition from the grain boundary response to the electrode one with temperature change was clearly evidenced in the low frequency range.     

Low dielectric loss,colossal permittivity,and high breakdown electric field in Al-doped Y2/3Cu3Ti4O12 ceramics

The miniaturization and high capacitance of electronic components are driving the development of high-performance electronic ceramic materials. In this work, we design a new strategy to achieve satisfactory dielectric properties with low loss, colossal permittivity, and a high breakdown electric field (E_b) in Al-doped Y_2/3Cu₃Ti₄O₁₂ (YCTO) ceramics prepared by a solid-phase synthesis method. The dielectric loss decreased with Al doping in the YCTO. The dielectric constant and the E_b were improved upon Al doping. With Al doping levels of 0.03 and 0.05, Y_2/3Al_0.03Cu_2.97Ti₄O₁₂ and Y_2/3Al_0.05Cu_2.95Ti₄O₁₂ ceramics displayed, respectively, a suppressed loss tangent of about 0.028 and 0.031, a high dielectric constant of approximately 9540 and 11792, and an E_b of approximately 4.32 and 4.54 kV/cm. The improved dielectric properties of the produced ceramics were closely linked to enhanced grain boundaries resistance. This study explores the physical mechanism behind the high performance of the YCTO-based ceramics, and also provides theoretical support for the application of devices comprising YCTO and related materials.     

Dielectric properties with high dielectric permittivity and low loss tangent and nonlinear electrical response of sol-gel synthesized Na1/2Sm1/2Cu3Ti4O12 perovskite ceramic

Giant dielectric ceramic, Na_1/2Sm_1/2Cu₃Ti₄O₁₂, was successfully prepared by a modified sol-gel method. X-ray diffraction experiments indicated that a body-centered cubic structure with a space group of Im3 was obtained. Our density functional theory calculations revealed that codoping Na and Sm in the CaCu₃Ti₄O₁₂ structure resulted in charge compensation between Na and Sm ions in this structure, whereas the oxidation states of Cu and Ti were unaltered. Giant dielectric permittivity ～7.21 × 10³ - 8.04 × 10³ and low dielectric loss tangent ～0.045–0.049 were accomplished at a sintering temperature of 1050 °C for 12–18 h. Nonlinear J - E property with breakdown electric field ～5.13 – 5.78 × 10³ V/cm and nonlinear coefficient ～6.08–6.82 were also achieved. The n-type semiconducting grain originated from short-range migrations of mixed Cu⁺/Cu²⁺ and Ti³⁺/Ti⁴⁺ charges. Finally, our charge analysis showed that the occurrence of Cu⁺ and Ti³⁺ was related to the existence of oxygen vacancy in these ceramics.     

Improved Dielectric and Nonlinear Electrical Properties of Fine‐Grained CaCu3Ti4O12 Ceramics Prepared by a Glycine‐Nitrate Process

Pure CaCu₃Ti₄O₁₂ was successfully prepared by a glycine‐nitrate process using a relatively low calcination temperature and short reaction time of 760°C for 4 h. Fine‐grained CaCu₃Ti₄O₁₂ ceramics with dense microstructure and small grain size were obtained after sintering for 1 h. The nonlinear coefficient of a fine‐grained CaCu₃Ti₄O₁₂ ceramic calculated in the range 1–10 mA/cm² was found to be very high of ~16.39 with high breakdown electric field strength of 1.46 × 10⁴ V/cm. This fine‐grained CaCu₃Ti₄O₁₂ ceramic also exhibited a very low loss tangent of 0.017 at 20°C with temperature stability over the range ?55°C to 85°C. The grain growth rate of the CaCu₃Ti₄O₁₂ ceramics was found to be very fast after increasing the sintering time from 1.5 to 3 h, leading to formation of a coarse‐grained CaCu₃Ti₄O₁₂ ceramic with grain size of about 100–200 μm. The dielectric permittivity of this coarse‐grained ceramic was found to be as high as 1.03 × 10⁵ with a low loss tangent of 0.054.     

Colossal dielectric permittivity and relevant mechanism of Bi2/3Cu3Ti4O12 ceramics

Bi_2/3Cu₃Ti₄O₁₂ (BCTO) ceramics with pure perovskite phase were successfully prepared by traditional solid-state reaction technique. Uniformly distributed and dense grains with the grain size of 2–3 μm were observed by SEM. A giant low-frequency dielectric permittivity of ~3.3×10⁵ was obtained. The analysis of complex impedance revealed that Bi_2/3Cu₃Ti₄O₁₂ ceramics are electrically heterogeneous. There are three kinds of dielectric response detected in Bi_2/3Cu₃Ti₄O₁₂ ceramics, which existed in the low-frequency range, middle-frequency range, and high-frequency range, respectively. Through the study of dielectric spectrum at different temperatures, the relatively low activation energy of 0.30 eV for middle-frequency dielectric response was calculated, which suggested that this Middle-frequency dielectric response can be ascribed to grain boundaries response. In view of the analysis of dielectric spectrum at low temperatures, the activation energy of 0.07 eV for high frequency dielectric response was found. This value illustrated that dielectric response at high frequencies was associated with grains polarization effect. The comparison of dielectric spectra of Bi_2/3Cu₃Ti₄O₁₂ ceramics with different types of electrodes revealed that giant low-frequency dielectric constant was attributed to the electrode polarization effect.     

A new perovskite-related ceramic with colossal permittivity and low dielectric loss

We designed a new type of perovskite-related dielectric energy storage material Na_1/3Cd_1/3Bi_1/3Cu₃Ti₄O₁₂ with colossal permittivity via an ordinary solid-state method. Remarkably, the Na_1/3Cd_1/3Bi_1/3Cu₃Ti₄O₁₂ ceramic sintered at 1030 °C displays a decent dielectric performance of colossal permittivity ∼1.5 × 10⁴ and low dielectric loss ∼0.04 at 1 kHz. Electric heterogeneity structure in Na_1/3Cd_1/3Bi_1/3Cu₃Ti₄O₁₂ ceramics was clarified, which consists of insulating grain boundaries and semiconducting grains. Notably, internal barrier layer capacitor effect was adopted to explain the decent dielectric performance based on the analysis of dielectric response behavior and complex impedance. Three dielectric anomalies were evidenced in dielectric temperature spectra. Our finding in this work not only explored the dielectric response of the new type of giant dielectric ceramics Na_1/3Cd_1/3Bi_1/3Cu₃Ti₄O₁₂ but also provided candidate materials for high energy storage density capacitors.     

Colossal dielectric permittivity and electrical properties of the grain boundary of Ca1−3x/2YbxCu3−yMgyTi4O12 (x=0.05, y=0.05 and 0.30)

Dielectric properties of Ca_1−3x/2Yb_xCu_3−yMg_yTi₄O₁₂ (x=0.05, y=0.05 and 0.30) prepared using a modified sol–gel method and sintered at 1070 °C for 4 h were investigated. The mean grain sizes of the CaCu₃Ti₄O₁₂ and co-doped Ca_0.925Yb_0.05Cu_3−yMg_yTi₄O₁₂ (y=0.05 and 0.30) ceramics were ≈15.86, ≈3.37, and ≈2.32 μm, respectively. Interestingly, the dielectric properties can be effectively improved by co-doping with Yb³⁺ and Mg²⁺ ions to simultaneously control the microstructure and properties of grain boundaries, respectively. These properties were improved over those of single-doped and un-doped CaCu₃Ti₄O₁₂ ceramics. A highly frequency−independent colossal dielectric permittivity (≈10⁴) in the range of 10²–10⁶ Hz with very low loss tangent values of 0.018–0.028 at 1 kHz were successfully achieved in the co-doped Ca_0.925Yb_0.05Cu_3−yMg_yTi₄O₁₂ ceramics. Furthermore, the temperature stability of the colossal dielectric response of Ca_1−3x/2Yb_xCu_3−yMg_yTi₄O₁₂ was also improved to values of less than ±15% in the temperature range from −70 to 100 °C.     

Colossal dielectric properties of Na1/3Ca1/3Sm1/3Cu3Ti4O12 ceramics: Computational and experimental investigations

A modified sol?gel technique was used to synthesize a high dielectric ceramic, Na_1/3Ca_1/3Sm_1/3Cu₃Ti₄O₁₂. The crystal structure of this sintered ceramic matches the standard pattern of a body?centered cubic (bcc) system within the Im3 space group (JCPDS No. 75–2188). No impurity phases were observed. Interestingly, a high dielectric permittivity of ～1.14–1.35 × 10⁴ and a low loss tangent of ～0.027–0.039 were achieved in this sintered Na_1/3Ca_1/3Sm_1/3Cu₃Ti₄O₁₂ ceramic. Our DFT calculations disclosed that substitution of Na⁺ ions at Cu²⁺ sites causes an observed excess Cu concentration. As a result, metastable insulating phases were formed at a relatively high sintering temperature. Additionally, our electron density calculations revealed that Na ions lose their electrons to Sm ions, whereas the oxidation states of Cu and Ti are unaltered. Our results show that Cu⁺ and Ti³⁺ were observed after introducing an oxygen vacancy into this lattice. Significantly different values of R_g, R_gb, and E_g, E_gb support an internal barrier layer capacitor as the most likely origin of the giant dielectric properties of this ceramic. XPS results show mixed Cu⁺/Cu²⁺ and Ti³⁺/Ti⁴⁺ in all ceramics, suggesting that electron hopping between Cu⁺?Cu²⁺ and Ti³⁺?Ti⁴⁺ is the probable origin of the n?type semiconducting state inside the grains.     

Low-temperature sintering and microwave dielectric properties of Nd(Co1/2Ti1/2)O3 ceramics using glass addition of oxides

The microstructures and microwave dielectric characteristics of complex perovskite Nd(Co_1/2Ti_1/2)O₃ ceramics with 60P₂O₅–15ZnO–5La₂O₃–5Al₂O₃–5Na₂O–5MgO–5Yb₂O₃ (PZLANMY) additions (1–4 wt%) prepared through the conventional solid-state route were investigated. It was found that Nd(Co_1/2Ti_1/2)O₃ ceramics can be sintered at 1210 °C owing to the sintering aid of PZLANMY-glass addition. At 1300 °C, Nd(Co_1/2Ti_1/2)O₃ ceramics with 1 wt% of PZLANMY-glass addition possess a dielectric constant (ε_r) of 27, a Q×f value of 64,000 GHz and a temperature coefficient of resonant frequency (τ_f) of ?29 ppm/°C. The PZLANMY-glass doped Nd(Co_1/2Ti_1/2)O₃ ceramics can find applications in microwave devices that require low sintering temperature.     

Macroscopic and Nanoscopic Polarization Relaxation Kinetics in Lead‐Free Relaxors Bi1/2Na1/2TiO3–Bi1/2K1/2TiO3–BiZn1/2Ti1/2O3

The stability of the field‐induced ferroelectric (FE) state was studied in relaxor lead‐free ceramics (1 ? y)[0.81Bi_1/2Na_1/2TiO₃–0.19Bi_1/2K_1/2TiO₃]–yBiZn_1/2Ti_1/2O₃ both macroscopically and microscopically. A strong dc electric field results in the formation of a stable FE state with a large piezoelectric coefficient for compositions with a small amount of Bi(Zn_1/2Ti_1/2)O₃, which are in the non‐ergodic relaxor state at room temperature. Increasing temperature promotes ergodic relaxor behavior, which is accompanied by the rapid destabilization of the induced state, that is, small relaxation times. Based on the obtained data, it is proposed that the depolarization is a two‐step process consisting of an initial realignment of the FE domains and their subsequent breakup into polar nanoregions. The ergodic relaxor behavior is also promoted by increasing the Bi(Zn_1/2Ti_1/2)O₃ content. The related charge disorder results in an enhancement of random electric fields and consequently a stable FE state cannot be induced even at room temperature.     

The Occupation Behavior of Y2O3 and Its Effect on the Microstructure and Electric Properties in X7R Dielectrics

The occupation behavior of Y₂O₃ in nonreducible BaTiO₃‐based ceramics was investigated thoroughly. Based on XRD, SEM, TEM‐EDS, and complex impedance analysis, it is ensured that there exists two turning points of Y₂O₃, 0.50 mol% and 1.00 mol%, and the latter is the solubility limit. Below 0.50 mol%, the introduced Y³⁺ ions precede to enter the A sites of the perovskite lattice, causing an observed enhancement in dielectric constant and energy storage density accompanied by an increase in grain size. Once the addition exceeds 0.50 mol%, the Y³⁺ ions will turn to occupy B sites to substitute for Ti⁴⁺ ions, leading to the significant reduction in dielectric constant and energy storage density. Above the solubility limit of 1.00 mol%, the excess Y³⁺ ions would segregate at grain boundary and even induce the formation of Y₂Ti₂O₇ phase, resulting in an abrupt enhancement of grain‐boundary resistance. Doped with 0.75–1.50 mol% Y₂O₃, all nonreducible specimens meet X7R requirement.