Electrical Properties Of Ceramics Research Articles

Enhanced optical and energy storage properties of K0.5Na0.5NbO3 lead-free ceramics by doping Bi(Sr0.5Zr0.5)O3

Transparent relaxation ferroelectric ceramics with excellent transmittance and energy storage density are indispensable for efficient multifunctional coupling. These ceramics have found extensive applications in transparent energy storage electronics, advanced pulsed power capacitors, and optoelectronic multifunctional devices. In this study, we employed a combination of strategies to enhance the optical and electrical properties of ceramics. Specifically, the breakdown field strength of potassium sodium niobate (KNN) was increased by introducing Bi(Sr0.5Zr0.5)O3 (BSZ), which reduced the ceramic grain size. The incorporation of polar nano-micro-regions led to stronger local polarity fluctuations on the nanoscale, effectively minimizing the residual polarization. Furthermore, the forbidden bandwidth of the system was widened to mitigate photoelectron optical energy loss during transition.The newly developed ceramic, (1-x) KNN-xBSZ, exhibited remarkable performance characteristics, including an energy storage density of 4.13 J/cm3, a recoverable energy storage density of 2.95 J/cm3 at a low electric field of 245 kV/cm, and an energy storage efficiency of 84 %. Additionally, at 700 nm, the 0.875KNN-0.125BSZ sample displayed a transmittance of 52 %. Notably, this ceramic demonstrated high power density (PD = 36.76 MW/cm3) and rapid charge/discharge rates (t0.9 = 0.94 μs). Moreover, it exhibited excellent temperature and frequency stability, making it a dependable option for optoelectronic devices utilizing transparent relaxation ferroelectric ceramics.

Fundamental study on the preparation of insulating ceramics via the phase reconstruction of phosphate tailings

Insulating ceramics with anorthite and diopside as the main crystal phases were manufactured using phosphate tailings, coal gangue, and quartz as raw materials, which were fired at 1160–1190 °C for 2 h. The structure and micromorphology of the samples were investigated using X-ray diffraction, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy. Dense ceramic samples exhibited an apparent porosity of less than 0.3%, densities of 2.64–2.86 g/cm3, bending strength of 127.71–172.73 MPa, dielectric constants of 6.98–7.79, and dielectric losses of 0.0086–0.0024 at 20 °C and frequency of 1 MHz. The effects of impurity elements on ceramic properties are determined. The excellent electrical properties can be attributed to the solid solution of iron in the crystalline phases, such as diopside, which reduce leakage conductance in ceramics and alleviate the influence of relaxation and space charge polarization on the electrical properties of ceramics. This study provides a new strategy for preparing high-value insulating ceramics from solid waste.

Effect of clay/nepheline tailing ratio on the dielectric relaxation and conduction mechanism of the conventional ceramic

The dielectric relaxation and conduction mechanism of 40 wt% nepheline tailing and 60 wt% clay-based ceramic, i.e., the 40/60 ceramic, have been investigated over wide ranges of frequency and temperature, using a broadband dielectric spectrometer (BDS) and then compared with the data recently reported for the 50/50 ceramic. Both 40/60 and 50/50 ceramics were fabricated by grinding the raw materials to be very fine, wet homogenously mixing, drying and finally firing at 1200 °C. Their crystalline phases identified by X-ray diffraction were quartz, hematite, cristobalite, and albite. The 40/60 ceramic of lower glassy phase (nepheline tailing) content displays lower crystallinity than the 50/50 ceramic. Its conduction activation energies (Eac) show values between 0.12 and 0.32 eV, corresponding to the activation energy of oxygen vacancies (Vo++ ~ 0.22 eV). As oxygen vacancies migrate at relatively low operating voltages, the fabricated ceramics would be promising in manufacturing the random access memory (RAM), taking into consideration that the 50/50 ceramic is more useful than the 40/60 ceramic. As a result, nepheline tailing or the glassy phase component may generate more oxygen vacancies and thus enhance the ceramic electrical properties. Finally, the conduction mechanism of both ceramics is described via the correlated barrier hopping (CBH) model.

Tailoring structure and piezoelectric properties of CaBi2Nb2O9 ceramics by W6+-Doping

Calcium bismuth niobate (CaBi2Nb2O9) is a typical bismuth-layer structured piezoelectrics (BLSPs) with a high Curie temperature (TC) of ∼943 °C, but it has low piezoelectric coefficient and high-temperature resistivity which severely limits signal acquisition in the high-temperature piezoelectric vibration sensors. Ion-doping modification is regarded as an effective way to enhance electrical properties. In this work, W6+ donor-doping at Nb5+ site in the CaBi2Nb2-xWxO9 (x = 0, 0.020, 0.025, 0.030, 0.035 and 0.040) piezoelectric ceramics with TC of 931 ± 2 °C were fabricated by the conventional solid-state reaction method. The effects of W6+-doping on crystal structure of CaBi2Nb2-xWxO9 as well as microscopic morphology and electrical properties of ceramics were investigated systematically. The tetragonality, isotropy and electrical properties of the ceramics were enhanced with the introduction of W6+ dopant. It was found that x = 0.025 was the optimal W6+-doping ratio that yielded remnant polarization of 8.0 μC/cm2, electrical resistivity of 3.0 × 106 Ω cm at 600 °C, piezoelectric coefficient (d33) of 14.4 pC/N, and good thermal depoling property. Our work has established a feasible approach to tune the structure of CaBi2Nb2O9 to improve piezoelectric properties for potential applications in high-temperature piezoelectric vibration sensors.

Structural, electrical and photochromic properties of Na0.5Bi4.5Ti4O15:xEr3+ ferroelectric ceramics

In view of the excellent piezoelectric performances of bismuth layered structure ferroelectrics at high temperature, Na0.5Bi4.5Ti4O15:xEr3+ ceramics have been successfully manufactured by the traditional high temperature solid state method. The influence of additive (Er3+) concentration on the phase structure, morphology and electrical properties of ceramics has been investigated. After Er3+ ion introduction, the ferroelectric properties are palpably enhanced, and the 2Pr reaches 30 μC/cm2 at x = 0.004. Furthermore, the ferroelectric domain structure of ceramics was characterized by PFM for the first time. Meanwhile, a reversible photochromic (PC) reaction and the associated luminescence modulation are achieved. It is found that a higher ΔIdec of 83.6% is obtained using down-conversion (DC) mode than up-conversion (UC) one. More importantly, an additional exposure to natural light can further enhance the ΔIdec from 73% to 80.5% after 407 nm irradiation. The present investigation suggests that the modified NBT ceramics with multiple performances facilitate the development of multifunctional materials used in electric devices, anti-counterfeiting and information storage.

Firing Temperature Effects on Phase Formation, Microstructure and Electrical Properties of BNKLT-Sm Ceramics

Lead-free Bi0.5(Na0.68K0.22Li0.10)0.5TiO3 + 0.003 mol Sm2O3 (BNKLT-Sm) ceramics were synthesized via the solid-state combustion technique with calcination temperatures between 750 and 850 °C and sintering temperatures between 1025 and 1100 °C for 2 h. The results showed that increasing the calcination temperature caused the percentage of perovskite phase and the particle size of the BNKLT-Sm powders increased. The BNKLT-Sm powder calcined at 800 °C displayed a pure perovskite structure without any impurity phases. The influence of the sintering temperature on the phase formation, microstructure and electrical properties of the ceramics was then investigated. All samples sintered at different temperatures possessed coexisting rhombohedral (R) and tetragonal (T) phases and the R phase became dominant when the sintering temperature increased. The microstructure of all ceramics showed a rectangular shape and anisotropic growth. The average grain size increased with increasing sintering temperature. Dielectric and ferroelectric behavior displayed relaxor characteristics in all samples. The maximum dielectric constant at Tm (εm ) of 4777 and the highest remnant polarization (Pr ) of 5.03 µC/cm2 were obtained by the densest ceramics (5.85 g/cm3), which was sintered at 1075 °C for 2 h.

Influence of CTO additives on microstructure and electrical properties of CCTO ceramics

CaCu3Ti4O12/CaTiO3(CCTO/CTO) composite ceramics were prepared through in-situ reaction and solid-state sintered at 1040°C for 10 h. The phase composition, microstructure, morphology, valence, and electrical properties of ceramics are systematically studied by X-ray diffraction(XRD), Field emission scanning electron microscopy(FESEM), Electron probe micro-analysis (EPMA), X-ray photoelectron spectroscopy(XPS), and LCR instruments. It can be found that the FESEM image shows that the addition of CTO inhibits the growth of CCTO grains, and there are nanocrystals inside the grains. The EPMA mapping demonstrated which nanocrystals are composed of CCTO and a small amount of CTO. Impedance spectroscopy observed two semi-circular arcs, which correspond to the effects of micron-level grains and nano-level nanocrystals, respectively. These two mechanisms significantly affect the colossal dielectric response of CCTO/CTO composite ceramics.

Relaxor behavior and superior ferroelectricity of Y2O3-doped (Ba0.98Ca0.02) (Ti0.94Sn0.04Zr0.02)O3 lead-free ceramics

To upgrade the electric properties of lead-free piezoceramics, (1–x)(Ba0.98Ca0.02Ti0.94Sn0.04Zr0.02)O3-xY2O3 (abbreviated as (1–x)BCTSZ-xY, x = 0 mol%, 0.02 mol%, 0.04 mol%, 0.06 mol%, 0.08 mol% and 0.1 mol%) ceramics were successfully synthesized by traditional solid-state sintering method. The phase structure and microstructure of ceramics were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and piezoresponse force microscopyeramics (PFM). The electric properties of ceramics were researched through piezoelectric, dielectric and ferroelectric test instruments. The results show that all samples have pure perovskite structure and favorable electric properties. The optimal electric properties which especially include superior ferroelectric properties are gained when Y2O3 content is 0.06 mol% (d33 = 419 pC/N, kp = 52%, Tc = 89.5 °C, εr = 26900, tanδ = 2.86%, Pr = 14.41 μC/cm2, Ec = 1.8 kV/cm). Moreover, the temperature-dependent dielectricity of samples shows apparent relaxor behavior under different frequencies. The Curie–Weiss law further proves that all samples are typical relaxor ferroelectrics, and the relaxor degree of samples decreases with increase of Y2O3 content. In conclusion, Y2O3 plays a significant role in enhancing electric properties of BCTSZ ceramics.

Effect of particle size distribution on functional properties of Ce0.9Y0.1O2-d ceramics

This paper has investigated the dependence of the mechanical and electrical properties of ceramics Ce0.9Y0.1O2-d (CeY) on changes in the proportion of submicron size particles in a powder with bimodal particle size distribution. The powder was prepared by mixing the products of sol-gel (submicron size fraction with average size of 0.2 μm and specific surface area of 39.52 m2/g) and solid-state synthesis (micron size fraction with average size of 5.68 μm and specific surface area of 4.81 m2/g) in a certain ratio to get different proportion of the fractions. All ceramics samples were formed by isostatic pressing with further annealing under identical conditions. The microstructure of ceramic samples was studied using scanning electron microscopy and static volumetric analysis. The impedance spectroscopy method has determined the temperature dependencies of the grain boundary resistance fraction, which are strongly related to the particle size distribution. The microhardness of samples was determined by the Vickers method. A nonlinear change of mechanical and electrical properties was found for the samples having approximately 20% content of submicron size particles. The dependence of the total electrical conductivity and the dependence of the microhardness on the particle size distribution possess the maxima and minima points for these compositions, respectively. The particle size distribution of powders has a strong impact on the ceramics formation process and allows to control the microstructure and physical properties of materials. We have proposed the ceramics model of “arched structure”, formed by bimodal compositions sintering, which allows to predict the properties of ceramics with other compositions.

The high piezoelectric properties of lead-free (1-x)(Ba0.85Ca0.15)(Ti0.9Zr0.1)O3-xLiTaO3-0.3 mol% GeO2 ceramics driven by multiphase coexistence

To optimize the comprehensive electrical performances of lead-free piezoelectric ceramics, (1-x)(Ba0.85Ca0.15)(Ti0.9Zr0.1)O3-xLiTaO3-0.3 mol% GeO2 (abbreviated as (1-x)BCZT-xLT-0.3 mol%G, 0 ≤ x ≤ 0.5) ceramics were prepared by conventional solid-state sintering method. The structures and electric properties of ceramics were systemically studied through XRD, Raman spectra, er-T, SEM, and P–E, respectively. The results show that the piezoelectric properties can be affected by phase coexistences for different doping contents. Thereinto, the phase coexistences change from R-O at x = 0 to R-O/O-T at 0.1 ≤ x ≤ 0.2 and O-T at x = 0.3, respectively, while the R single phase is detected with x further increasing to 0.5. Correspondingly, the ceramics with multiphase coexistences at 0 ≤ x ≤ 0.3 obtain more excellent electrical properties than the ones with single phase at x = 0.5. In addition, the outstanding electric properties especially including the piezoelectric response are achieved at x = 0.2 mol% (e.g., d33 = 570 pC/N, kp = 0.61, er = 14,887, tanδ = 0.007, Pr = 8.51 µC/cm2, Ec = 0.18 kV/cm, respectively).

Conceptual Framework for Dislocation-Modified Conductivity in Oxide Ceramics Deconvoluting Mesoscopic Structure, Core, and Space Charge Exemplified for SrTiO3.

The introduction of dislocations is a recently proposed strategy to tailor the functional and especially the electrical properties of ceramics. While several works confirm a clear impact of dislocations on electrical conductivity, some studies raise concern in particular when expanding to dislocation arrangements beyond a geometrically tractable bicrystal interface. Moreover, the lack of a complete classification on pertinent dislocation characteristics complicates a systematic discussion and hampers the design of dislocation-modified electrical conductivity. We proceed by mechanically introducing dislocations with three different mesoscopic structures into the model material single-crystal SrTiO3 and extensively characterizing them from both a mechanical as well as an electrical perspective. As a final result, a deconvolution of mesoscopic structure, core structure, and space charge enables us to obtain the complete picture of the effect of dislocations on functional properties, focusing here on electric properties.

Effects of (K0.5Na0.5)(Nb0.96Sb0.04)O3 on microstructure and electrical properties of BNT-based piezoelectric ceramics

In this work, (1-x)Bi0.5Na0.5TiO3-x(K0.5Na0.5)(Nb0.96Sb0.04)O3 [abbreviated as (1-x)BNT-xKNNS] lead-free piezoelectric ceramics were successfully prepared by the conventional solid-state reaction method, and effects of (K0.5Na0.5)(Nb0.96Sb0.04)O3 [abbreviated as KNNS] on microstructure structure and electrical properties of the ceramics were systematically discussed. Results of phase characterizations showed that KNNS led to phase transition from orthorhombic (O) phase to monoclinic (M)-O phase coexistence. However, KNNS had small effects on grain growth of the ceramics according to scanning electron microscope (SEM) analysis. The existence of KNNS resulted in unique dielectric relaxor behavior of such ceramics, i.e. vanished depolarization temperature (Td) and insensitive relative dielectric constants (εr) to frequencies when T < Ts. When T ≥ Ts, obvious frequency dispersion of εr resulted from thermally-activated B-site disorder. Furthermore, electrical properties and energy storage properties were studied and the ceramics with x = 0.02 possessed optimized dielectric properties of εr ~ 773 (@100 kHz) and dielectric loss (tanδ) ~ 0.02 over wide temperature range.

Fabrication and Electrical Characterization of Lead-Free BiFe0.91(Mn0.47Ti0.53)0.09O3–BaTiO3 Ceramics

The (1-x)BiFe0.91(Mn0.47Ti0.53)0.09O3–xBaTiO3 (BFMT–BT) lead-free ceramics have been fabricated by the conventional solid-state reaction method. The phase structure of BFMT-BT investigated by X–ray diffraction shows a single perovskite phase. Although 20% mol of Bi2O3 was added to the raw materials, the evaporation of Bi3+ ions during calcining and sintering processes is from 20 to 30% wt. relative to other elements. The effect of BaTiO3content on electrical properties of BFMT-BT ceramic has been investigated. At BaTiO3concentration of 0.3 mol and the sintering temperature of 950oC, electrical properties of ceramics are best with the density (r) of 7.6 g/cm3, the electromechanical coupling factor (kp) of 0.28, the dielectric constant (εr) of 1028, and the difference in polarizations at zero field is about 10.5 mC/cm2.

Dielectric SrTiO3 mesocrystal derived from a H2Ti4O9·H2O single crystal

Strontium titanate (SrTiO3, ST) is a typical paraelectric material that has been widely used in many fields as a dielectric material and an energy-storage material, especially in the electronics industry, due to its excellent dielectric properties. Herein, we report the preparation of pure ST polycrystal powder with uniform granules by the solvothermal treatment of layered titanate H2Ti4O9·H2O (HT) and Sr(OH)2·8H2O as the raw materials. The effects of specimen morphology and electric field strength on the electrical properties of ST ceramics were investigated by studying their responses to heat treatment at various temperatures. The results show that pure ST mesocrystals, nanoparticles, and ceramics were successfully prepared. The ST ceramics show a rare bimodal phenomenon and strong dielectric response, which is due to the specimens containing two forms of ST crystal structure, namely the traditional ST polycrystal and a rare ST mesocrystal. When sintered at 900 °C, the ST ceramic exhibited good electrical-response performance due to the uniform particle morphology of the specimen and a large electric field strength at 2 kV. This study demonstrates the influence of particle morphology and electric field strength on the electrical properties of ceramics and lays the foundation for the development of multifunctional oxide ceramics with excellent electrical properties.

From core–shell particles to dense Ba0.8Sr0.2Zr0.1Ti0.9O3@Bi2O3–Fe2O3–SiO2 ceramics with low sintering temperature and improved dielectric, energy storage properties

To achieve high energy storage in dielectric ceramics, a new designed material Ba0.8Sr0.2Zr0.1Ti0.9O3@Bi2O3–Fe2O3–SiO2 with core–shell structure was fabricated by the monodispersed submicron Ba0.8Sr0.2Zr0.1Ti0.9O3 particles (diameter ~ 180 nm) coated with the 25-nm-thick shell of Bi2O3–Fe2O3–SiO2. The influences of Bi2O3–Fe2O3–SiO2 amount, Bi/Fe ratio, and sintering temperature on the phase composition, microstructure, and ceramic electrical properties were investigated. X-ray diffraction analysis of the ceramics revealed the formation of perovskite Ba0.8Sr0.2Zr0.1Ti0.9O3 when the Bi2O3–Fe2O3–SiO2 amount was below 6.0 wt%. The secondary phases Bi2Fe4O9 and Bi4Ti3O12 formed in ceramics when the Bi2O3–Fe2O3–SiO2 amount exceeded 6.0 wt%, as the ceramic grain core–shell structure collapsed. Based on FESEM images, the densification of ceramics can be tenderly controlled at low sintering temperature, and the ceramic grains can maintain their core–shell structure. As the Bi2O3–Fe2O3–SiO2 amount, the ratio of Bi to Fe, and the sintering temperature increase, the ceramic room temperature dielectric constant increases up to a maximum value then decreases. The energy storage density exhibits a similar tendency to increase first and then decrease. Fine-grained Ba0.8Sr0.2Zr0.1Ti0.9O3@Bi2O3–Fe2O3–SiO2 ceramics with Bi/Fe ratio of 1.04 and 6.0 wt% Bi2O3–Fe2O3–SiO2 sintered at 1120 °C had a dielectric constant of 2599, the maximum energy storage density of 1.50 J/cm3 under 29.31 kV/mm. This work proposed a novel method to enhance electrical properties of functional materials, which could be potentially used in the fabrication of capacitors with high energy storage performance.

Influence of different lanthanide ions on the structure and properties of potassium sodium niobate based ceramics

Different lanthanides (La, Ce, Pr, Nd, Sm, Ho, Er and Yb) doped potassium sodium niobate [(K,Na)NbO3, KNN] based ceramics are fabricated through solid-state method to study the influences and connections of lanthanides on phase structures, microstructures, electrical properties of ceramics. The coexistence of rhombohedral and tetragonal phases is possessed in the ceramics. The fractions of tetragonal phase increase firstly and decrease with decreasing the dopant ionic radius. Higher tetragonal phase fraction and large tetragonality can be beneficial to properties. The Nd3+ doped ceramics present good combination properties (TC = 223 °C, d33 = 400 pC/N, d33* = 530 pm/V, kp = 0.46).

Effects of Ho2O3 doping and sintering temperature on the core-shell structure of X9R Nb-modified BaTiO3-(Bi0.5Na0.5)TiO3 ceramics

The amphoteric element holmium was used to dope X9R Nb-modified BaTiO3-(Bi0.5Na0.5)TiO3 ceramics (BTBNT-Nb) by a conventional solid-state reaction method. The effect of Ho2O3 doping on the dielectric and electric properties of ceramics were investigated. X-ray diffraction results showed that the rare earth of Ho3+ can occupy A- and B-sites of BTBNT-Nb. All samples met X9R specifications and the insulation resistance of the 0.5 mol% Ho2O3 doped ceramic was 1.05 × 1013 Ω/cm. The sintering temperature strongly influenced the core–shell structure of ceramics Transmission electron microscope images revealed that the size of ferroelectric domain in the core decreased with increasing temperature. Multilayer ceramic capacitor chips with ten active dielectric layers were prepared and characterized.

Effects of V2O5 doping on the structure and electrical properties of BCZT lead-free piezoelectric ceramics

Lead-free (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3-x mol%V2O5 (x = 0, 0.05, 0.15, 0.20 and 0.50) were fabricated successfully via solid-state reaction route and the effects of V2O5 doping on the phase composition, microstructure and electrical properties of the ceramics have also been studied. The results indicated that the addition of V2O5 significantly lower the sintering temperature of BCZT ceramics to 1350 °C without sacrificing the high piezoelectrical properties. XRD results revealed that the phase structure was not changed with the introduction of V2O5. The sinterablity results and the SEM graphs indicated that small amount of V2O5 could effectively increase the density and grain size of BCZT ceramics. However, the electrical properties of BCZT ceramics deteriorate rapidly when the amount of V2O5 up to 0.5 mol%. Thus, the piezoelectrical properties of BCZT-xV ceramics could be obtained at x = 0.2 mol%, which were as following: d33 = 466 pC/N, kp = 32.5%, Qm = 162, Pr = 7.735 µC/cm2, er = 3104 and tan δ = 0.03, implying promising applications for lead-free piezoelectric ceramics.

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

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

The effect of dispersant on the properties PSN-PMS-PNN-PZT piezoelectric ceramics

Pb(Sb1/2Nb1/2)0.01(Mn1/3Sb2/3)0.01(Ni1/3Nb2/3)0.5(Zr0.3Ti0.7)0.48O3 piezoelectric ceramics were prepared by traditional solid-state sintering method. Firstly, the dispersant of PSN-PMS-PNN-PZT piezoelectric ceramics was determined and the effect of dispersants doping on the phase structure, microstructure morphology and electrical properties of ceramics was studied. The results show that all samples are single perovskite phase. When both balls are added to the dispersant, ceramics exhibit the optimum properties: d33 = 907 pC/N, εr = 6889, kp = 65.62%, tanδ = 1.53%. Performance of the sample has been greatly improved compared with that without dispersant doping.