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Energy storage dielectric ceramics play a more and more important role in power or electronics systems as a pulse power material, and the development of new technologies has put forward higher requirements for energy storage properties. Here, the sol-gel method was used to synthetize the 0.9BaTiO3-0.1Bi(Mg1/2Zr1/2)O3 (0.9BT–0.1BMZ) precursor powder and 0.9BT-0.1BMZ ceramics with pseudocubic phase was obtained. The 0.9BT-0.1BMZ dielectric ceramics possessed a strong relaxation behavior with 1.64 relaxation degree (g) and 0.15 eV relaxation activation energy (Ea) fitted by modified Curie–Weiss law and Vogel-Fulcher formulas, respectively. The most important was that by controlling the grain size to be reduced, the discharge energy storage density had been improved to 2.0 J/cm3 with high breakdown strength (325 kV/cm). In addition, the comprehensive analysis of electric field distributions, breakdown paths, and impedance spectra was illustrated the enhanced grain boundary effect can improve the energy storage performance obviously.

The epoxy resin (E-51) was used as polymer matrix, conductive carbon black (CB) as conductive filler, and PZT was used to prepare a composite by curing. The effects of PZT and CB content on the properties of PZT/ CB/ EP piezoelectric composite were studied. When the PZT content reaches 40 wt%, the optimized vibration attenuation properties of PZT/CB/EP materials could be achieved with a loss factor of 0.9 from room temperature to 60 °C. With the increase of PZT content, the bending strength of PZT/CB/EP piezoelectric composite vibration reduction material firstly increased from 45 MPa to 65 MPa and then decreased to 38 MPa. At room temperature, the dielectric constant increased from 7 to 50, and the dielectric loss increased from 0.1 to 0.5.

0.5wt%MnO2-doped (1 − x)BaTiO3–xBiCoO3 ceramics short as (1 − x)BT–xBC–M sintered in air and reducing atmosphere via solid-state process were investigated. The X-ray diffraction results showed that solid solubility in (1 − x)BT–xBC ceramics sintered in the air was higher than that in reducing atmosphere. (1 − x)BT–xBC–M ceramics sintered in air transformed from tetragonal to pseudo-cubic phase when x ≥ 0.1. The scanning electron microscopy results indicated that the average grain size increased with the BC component increasing; however, opposite phenomena occurred in samples sintered in the reducing atmosphere. The dielectric temperature curves of samples sintered in reducing atmosphere were flatted with excellent insulation resistivity of an order of magnitude of 1013 Ω·cm, while anomalous dielectric constant and dielectric loss of samples sintered in the air with deteriorated insulation resistivity of an order of magnitude of 107 Ω·cm. The anti-reduction mechanism of (1 − x)BT–xBC–M system was explained by the “electron–hole” trapping effect and formation of defect dipoles $$\left[ {{\text{Mn}}_{{{\text{Ti}}}} ^{{\prime \prime }} - V_{{\text{O}}}^{{ \cdot \cdot }} } \right]$$ and $$\left[ {2{\text{Co}}_{{{\text{Ti}}}} ^{\prime } - V_{{\text{O}}}^{{ \cdot \cdot }} } \right]$$ .

Effects of different sintering atmospheres (O2 and air) on the energy storage properties and dielectric characteristics were systematically investigated for 2MgO–2Al2O3–5SiO2 (MAS)-coated Er0.02Sr0.97TiO3 (EST) ceramics. The core–shell structure was formed by the sol-precipitation method. The ceramic sintered in O2 features fine grain, excellent frequency stability, low leakage current, high dielectric breakdown strength (BDS), and high energy storage density (Wreco). Compared with air-sintered ceramics, the dielectric DC breakdown strength of ceramic sintered in oxygen atmosphere has been enhanced significantly from 375 to 590 kV/cm. Besides, the maximum Wreco of 2.01 J/cm3 and efficiency of 86.2% were obtained at 460 kV/cm, which demonstrated that the core–shell structure and atmosphere sintering provide an instructive strategy for the design of high energy storage materials.

BaTiO3@xMgO (BT@xMg, x = 0–7 mol%) ceramics were prepared by MgO-coated BT powders, which were synthesized by a chemical precipitation method. The effects of MgO coating on the phase structure, microstructure and dielectric properties of BT@xMg ceramics were explored. The solid solubility of Mg2+ at B-site in BT was about 0.8 mol%, which was confirmed by the c/a ratio variation. When x

Effects of sintering temperatures on the phases, microstructures, defect structures and dielectric behaviors of the SrTi0.985(Nb2/3Zn1/3)0.015O3 ceramics have been systematically investigated. Giant permittivity (~ 10100) and low tangent loss (~ 0.035) are achieved in the ceramics sintered at 1500 °C. With an increase in sintering temperature, the grain size increases first and then stabilizes gradually, while the lattice constant increases first and then decreases. Higher sintering temperature is beneficial to the thermal stabilities of permittivity and tangent loss. Further investigations reveal that the giant permittivity mainly results from defect polarization. More Ti3+ ions and more oxygen vacancy-related defect complexes ( $$ {\text{Ti}}^{3 + } - {\text{V}}_{\text{O}}^{ \cdot \cdot } - {\text{Ti}}^{3 + } $$ and $$ {\text{V}}_{\text{O}}^{ \cdot \cdot } - {\text{Zn}}_{\text{Ti}}^{\prime \prime } $$ , etc.) are involved in the ceramics sintered at 1500 °C, contributing to the giant permittivity and low tangent loss. The presence of point defects breaks the local structural symmetry and distorts the oxygen octahedron. Dielectric properties are deteriorated at excessive sintering temperature due to the dissociation of defect complexes as well as the enhanced interfacial polarization.

(1−x)[0.94Bi0.5Na0.5TiO3 – 0.06BaTiO3]−xLa0.33NbO3 (x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) (BNBT-LN) bulk lead-free relaxor ferroelectric ceramics were synthesized via solid-state sintering method. Phase, microstructure and energy storage properties were determined. The X-ray diffraction (XRD) revealed a single perovskite phase for compositions of x ≤ 0.02, while the second phase of Bi2Ti2O7 along with the parent phase for x ≥ 0.04. Dense microstructure with a decrease in grain size has been achieved via LN doping. The addition of LN decreased the remnant polarization (Pr), and coercive field (Ec), while increased the difference between the maximum polarization (Pmax) and remnant polarization (Pr). The high energy-storage density of 2.96 J/cm 3 and high recoverable energy density of 1.66 J/cm3 at a breakdown electric field of 214 kV/cm were achieved for the composition of x = 0.02 with good temperature stability satisfying the condition of Δer /e r200 °C ≤ ± 15% in a working temperature range of 70 °C to 400 °C. Similarly, a less discharge time of

Solid-state sintering method was used for the synthesis of Mg1−xCoxSiO3 (x = 0–0.25) ceramics. Phase, microstructure and microwave dielectric properties of the ceramics were investigated. With increase in Co2+ content, the increase was observed in the lattice parameters. The Qufo value of MgSiO3 was enhanced from 103,453 to 145,846 GHz with increasing the value of x content from 0 to 0.15. The Co2+ substitution also led to an obvious decrease in the sintering temperature by ~ 100 °C. Clino-enstatite phase formed for the composition with x = 0 while Proto-enstatite formed as the major along with minor clino-enstatite phase for the compositions with x > 0. Good dielectric properties at microwave frequencies i.e. er ~ 8.11, Qufo ~ 145,846 GHz and τf ~ − 12 ppm/°C were obtained for the composition with x = 0.15 sintered at 1350 °C for 9 h. This is suggested to be a very favorable dielectric material for millimeterwave applications.

Phase, microstructure, and microwave dielectric properties of (Mg0.95Co0.05)(Ti1−xSnx)O3 (0.05 ≤ x ≤ 0.20) ceramics prepared via the conventional solid-state route were investigated. X-ray diffraction analysis showed the existence of a single phase for the compositions with Sn4+ ≤ 0.15; however, a further increase in Sn4+ caused the formation of a secondary SnO2 phase in the ceramics. The maximum observed densities of the single phase ceramics were higher than 95% of the theoretical density. An increase in the lattice parameters of the ceramics were observed with an increasing Sn4+ content. Dense microstructures were observed for the single phase ceramics at a sintering temperature of 1400°C, whereas a porous microstructure was observed for the ceramics with secondary phase. The unloaded quality factor (Qufo) of the ceramics was found to increase initially with an enhancing Sn4+ content from 0.05 up to 0.15; however, a sudden downfall was detected with a further enhancement in Sn4+. The dielectric constant and temperature coefficient of resonant frequency of the ceramics were observed to decline monotonically with enhancing Sn4+ content.

Structure and electrical properties of Mn-doped (0.6 − x)Pb(Mg1/3Ta2/3)O3–xPbZrO3(PZ)–0.4PbTiO3 (PMT–PZ–PT) ceramics with morphotropic phase boundary were studied (x = 0.2 and 0.25). The tetragonal intensity ratio TP (%) of Mn doped 0.4PMT–0.2PZ–0.4PT samples was calculated based on Raman spectra. The TP (%) values were found to increase with MnO2 doping, being from 67.6 to 78.3%, then decrease sharply at the doping limit of 0.8 wt%. The X-ray diffraction (XRD) pattern of Mn 0.2 wt% doped 0.35PMT–0.25PZ–0.4PT sample indicates the existence of more tetragonal phase at room temperature, where the XRD peaks become broader over temperature range of 90–160 °C, induced by the rhombohedral to tetragonal phase transition. The remnant polarization (Pr) was found to increase with increasing Mn doped level, while the coercive field shown contrary trend. Due to the “hardening” effect caused by the Mn addition (acceptor dopant), the dielectric constant and dielectric loss of 0.35PMT–0.25PZ–0.4PT ceramics were found decreased, while the mechanical quality factors were found increased up to 790. Of particular interest is that the piezoelectric coefficient (d33 ~ 435pC/N) and electromechanical coupling factors (kp = 59%) were found to increase with Mn addition, showing a “softening” effect, due to the existence of oxygen vacancies, which may improve the sinterability of the ceramics at high temperature.

The fundamental characteristics of varied initial core-sizes of BaTiO3(BT) and its influential role on the morphology and dielectric properties of BaTiO3@0.6BaTiO3-0.4BiAlO3(BT@0.6BT-0.4BA) ceramic samples were studied. Alkoxide sol-precipitation method was adopted as revised chemical route to synthesize the constituent “core” BT powders in a dispersed phase, whereas the distinctive initial nano-sized particles were affected by the pre-calcination temperatures (600-900 °C).The microstructure of the uncoated BT ceramics revealed an exaggerated grain growth with an optimized dielectric constant (emax >9 000) whilst the coated ceramics behaved otherwise (grain growth inhibited) when sintered at an elevated temperature. Regardless of the previously studied solubility limit (about 0.1%) of BT-BA samples, BT@0.6BT-0.4BA maintained a maximum dielectric constant (emax) ranging from 1 592 to 1 708 and tan δ less than 2% under a unit mole ratio at room temperature. In view of all these analyses, the initial nanometer sizes of the as-prepared BT-core powders combined with the increase effect of cation substitutions of Bi3+ and Al3+ in the shell content, induced the diffuse transition phase of BT@0.6BT-0.4BA composition.

The pure and Sm modified SrTiO3 ceramics have been fabricated by solid state reaction method at different atmospheres, including ambient, reduced and oxidized conditions. All studied ceramics are in single cubic perovskite phase with high bulk density, where Sm doped ceramics possess decreased grain size. The room temperature permittivities of Sr0.97Sm0.02TiO3 and Sr0.98Sm0.02TiO3 sintered in N2 were found to be on the order of 25120 and 13370 at 1 kHz with dielectric loss being 0.044 and 0.008. The giant permittivities were associated with the increase of Ti3+ ions, which were due to the combination of Ti4+ ions and electrons. With increasing Ti3+ ions, the concentration of Ti4+ ions, Ti3+ ions and $${\text{V}}_{{\text{O}}}^{{ \cdot \cdot }}$$ reach the balance where the defect dipoles [ $${\text{T}}{{\text{i}}^{4+}} \cdot {\text{e}} - {\text{V}}_{{\text{O}}}^{{ \cdot \cdot }} - {\text{T}}{{\text{i}}^{4+}} \cdot {\text{e}}$$ ] were created, responsible for the low dielectric loss.

Mn-doped barium strontium titanate Ba0.4Sr0.6TiO3-x mol%Mn (x = 0, 1, 3 and 5; BSTMx) thin films were deposited on Pt/Ti/SiO2/Si(100) substrates by spin-coating and annealed at 800 °C. X-ray diffraction patterns revealed that all the thin films were a typical cubic perovskite structure and no impurity peaks were observed. The effect of Mn doping on the ferroelectric properties and energy storage performance of the samples was investigated. The results showed that the recoverable energy storage density Urec and the difference ∆P(Pmax − Pr) between maximum polarization Pmax and remnant polarization Pr firstly increased, then decreased with the increase of Mn doping amount. The optimized energy storage performance was obtained in Pt/BSTM3/Pt thin films: energy storage density of 8.48 J/cm3 and energy storage efficiency of 42.4% at 1.63 MV/cm, electrical resistivity of 4.19 × 1010 Ω cm and leakage current density of 7.77 × 10−6 A/cm2 at 163 kV/cm. Moreover, the effect of different top electrodes on energy storage performance was studied, which displayed that the energy density of Au/BSTM3/Pt films was higher than that of Pt/BSTM3/Pt films. The results indicated that Mn doping and Au electrodes could be effective ways to improve the energy storage properties of BST thin films.

We investigated the structure, dielectric properties and energy density performances of cubic perovskite-structured Mg-doped SrTiO3 ceramics that were prepared by the solid-state reaction method. SrTiO3 ceramic exhibited a relatively stable permittivity about 265–290 and enhanced dielectric breakdown strength (DBS) by Mg isovalent doping. Doping effects on the energy-storage properties in SrTiO3 ceramics was performed by complex impedance analysis and polarization–electric field hysteresis loops. The energy storage density was dependent on DBS while energy efficiency was closely related to the remnant polarization. The possible physical mechanisms, including grain, gain boundary and interfacial polarization effects, were discussed to explain the improvement of dielectric breakdown strength. The bulk Mg-doped SrTiO3 materials have shown interesting energy densities (1.86 J/cm3) with good energy storage efficiency (about 89.3%) indicating that they can be a promising candidate for high energy density capacitor applications.

Nb2O5 doped 0.8BaTiO3–0.2(Na1/4Bi3/4)(Mg1/4Ti3/4)O3 (0.8BT–0.2NBMT) polycrystalline ceramics were prepared by solid state reaction method. 0.8BT–0.2NBMT samples were observed to possess two dielectric peaks, which were attributed to the formation of core–shell structure (Huang et al. in J Eur Ceram Soc 36:533–540, 2015). Longer sintering induced uniform distributions of the additives. The introduction of Nb2O5 into 0.8BT–0.2NBMT could obviously bring about the improvement of the dielectric temperature stability, the degradation of the dielectric loss at room temperature and the decrease of the sintering temperature. The 0.8BT–0.2NBMT ceramics doped with 2.0 at% Nb2O5 could satisfy the temperature range of the X9R (−55 to 200 °C, △C/C25°C = ±15% or less) characteristics, with a moderate dielectric constant of 1130, low dielectric loss of 0.7%, low sintering temperature of 1050 °C and insulation resistivity of 5 × 1012 Ω cm at room temperature, which might be promising for practical use in multilayer ceramic capacitors. The inhomogeneous distribution and the existence of the secondary phases were responsible for this excellent dielectric temperature characteristic. The complex impedance analysis was introduced to elaborate the conduction mechanism.

The ceramics were prepared using the solid-state reaction method and their phase, microstructure and microwave dielectric properties were investigated. A single-phase clinoenstatite system with monoclinic structure (space group P21/c) was confirmed through x-ray diffraction (XRD) analysis for the compositions with x ≤ 0.1. The compositions with x ≥ 0.15 contain SiO2 and (Mg1−x Ni x )2SiO4 phases only as confirmed from the XRD data of their sintered samples. The unit cell volume was decreased while the theoretical density was increased with increase in x from 0 to 0.1. A decrease in dielectric constant (e r) while an increase in unloaded quality factor multiplying the resonant frequency (Q u f o) and temperature coefficient of resonant frequency (τ f) was observed with increase in Ni content from 0 to x = 0.1. In the present study, e r ∼ 6.10, Q u f o ∼ 118,702 GHz and τ f ∼ −10 ppm/°C was achieved for the composition with x = 0.1 sintered at 1425°C for 9 h. The material is a good candidate for millimeter wave applications.

The 0.6Bi0.5Na0.5TiO3–(0.4 − x)NaNbO3–xBa(Zr0.2Ti0.8)O3 (BNT–NN–BZT) ceramics were developed for application as high energy density capacitor by conventional solid-state reaction method, and their structure, dielectric and ferroelectric properties were investigated in detail. When BZT was introduced into the system, the crystal structure changed from tetragonal to pseudocubic. Temperature dependent dielectric permittivity showed a broad maximum in these pseudocubic ceramics, exhibitting distinct relaxor feature. The relaxor behavior was evaluated by modified Curie–Weiss and confirmed to be enhanced with increasing BZT content. Benefited from the relaxor feature, its dielectric constant and dielectric temperature stability were largely improved. The remanent polarization (Pr) and coercive electric field (Ec) decreased with high BZT content and the maximum polarization (Pm) improved as shown in ferroelectric hysteresis loops (P–E loops). The energy storage property was also improved with increasing BZT, the optimized energy storage property was obtained in x = 0.20 sample with W = 1.69 J/cm3 at 17.5 kV/mm, which was superior to many other ferroelectric relaxors, indicating that BNT–NN–BZT ceramics were promising candidates for temperature stable energy storage applications.

In this paper, 0.6(Na0.5Bi0.5)TiO3–0.4NaNbO3(0.6NBT–0.4NN) was synthesized by solid state reaction method. The homogenous green ceramic sheets with high density were produced by tape casting according to suitable casting parameters. Embryos of multilayered ceramic capacitors (MLCC) had been fabricated by punching, screen printing, stacking, laminating and cutting processes. And then after burning out and sintering at different conditions, the cross-sectional microstructures of components were compared. Differential scanning calorimetric analysis and the thermo-gravimetric analysis of green devices were carried out to analyze the effects of different sintering procedures on MLCCs. The dielectric properties and polarization loops of the MLCCs were investigated with dielectric constant (800–895), dielectric loss (0.004–0.007) and capacitance variation ΔC/C

A lead-free ceramics (1 − x)(0.84Na0.5Bi0.5TiO3–0.16K0.5Bi0.5TiO3)–xK0.5Na0.5NbO3 (x = 0, 0.03, 0.06, 0.09, 0.12, 0.15) for energy-storage application have been fabricated by conventional solid state method. All compositions were crystallized into perovskite solid solution structure ascertained by XRD. SEM micrograph revealed that homogeneous grain could be obtained by addition of appropriate K0.5Na0.5NbO3 (KNN). The depolarization temperature (Td) decreased significantly from 140 to 70 °C, while the maximum dielectric constant temperature (Tm) reduced slightly with increasing KNN. And the addition of KNN improved the energy-storage properties significantly by weakening the ferroelectricity of Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3 (NBT–KBT) ceramics. When x = 0.09, the highest energy-storage density (W = 1.51 J/cm3) and energy efficiency (η = 65.0 %) were obtained at room temperature. Besides, the temperature stability of energy-storage density could satisfy ΔW/W100°C ≤ ±20 % when the addition of KNN was over 0.09 from 20 to 150 °C.

Based on (1 − x)(0.92Bi0.5Na0.5TiO3–0.08BaTiO3)–xNa0.73Bi0.09NbO3 ((1 − x)BNTBT–xNBN) lead-free ternary solid solution, a new energy-storage ceramic system was prepared and firstly reported in this study. The solid solubility of no more than 10 mol% for NBN was revealed by XRD characterization. Growing grains up to ~1.6 μm grain size and obviously broadened er versus T response were observed with increasing NBN from 10 to 40 mol%, indicating the greatly improved dielectric temperature stability. For sample with x = 0.20, optimized energy-storage properties with W = 1.36 J/cm3 and η = 73.9 % were achieved, together with a wide temperature range of −12 to 300 °C with ∣TCC∣ ≤ 15 %, showing potential for high temperature energy-storage applications.

0.85 Ba(Ti0.96Zr0.04)O3–0.15 Bi(Mg0.5Ti0.5)O3 relaxor ferroelectric ceramic samples were synthesized through traditional solid state reaction method. The asymmetric single peak of (200) at 45° was revealed by XRD measurement, combined with diffuse phase transition peaks in dielectric-temperature spectrum and a slim but discernible hysteresis loop, which proved the existence of the polar nano-regions (PNRs) in paraelectric matrix of the sample. The investigation of dielectric response of the ceramic samples under electric field (changing field magnitude and field history) was employed to analysize the evolution of PNRs. Electric field dependence of dielectric constant was obtained both by small signal bias electric field measurement and differential calculation from P–E curves, they all reached the maximum value firstly at the critical electric field and then decreased with the continuous increasing of electric field, instead of decreasing directly. However, the value of dielectric constant and critical field of bias electric field measurement was hysteretic electrically to those of differential calculation from P–E curves. Both the glassy model and macro–micro theory model were employed to explain and explore the evolution of PNRs, though from different perspective.

(1 − x)BaTiO3–xBi(Y0.5Yb0.5)O3 (BT–BYYb, x = 0.01–0.12) ceramics were prepared via solid-state processing techniques. The structure, dielectric and impedance properties of (1 − x)BT–xBYYb ceramics are studied. The studies show that the ceramics are in tetragonal phase when x ≤ 0.07, transform to pseudocubic phase at x ≥ 0.08. The grain growth is obviously suppressed for (1 − x)BT–xBYYb samples with x value. Dielectric properties are depressed and dielectric peaks are broadened with x. Tm first increases and then decreases. BT–BYYb system exhibits diffused phase transition and good temperature stability, which is due to the increased cation disorder, forming the local difference of the polar region due to the size and charge difference and inducing many different regions with different Curie points. The samples can meet the temperature requirements of X8R characteristics at 1 kHz with: e ~ 1330, tanδ ~ 0.0076, |△C/C| ≤ ±15 % (−55 to 150 °C) for x = 0.11 and e ~ 1032, tanδ ~ 0.012, |△C/C| ≤ ±15 % (−55 to 170 °C) for x = 0.12, respectively. The activation energy of the bulk material obtained from conduction and relaxation first increases and then decreases with increasing BYYb concentration. The different activation energy indicates various mechanisms are involved in the conduction and relaxation process, which may be due to the mixed conduction or doubly ionized oxygen and thermal motions of titanium ions (Ti4+) or doubly ionized oxygen, respectively.

The energy storage properties of Ca-doped (Sr, Ca)TiO3 (SCT) paraelectric ceramics have been intensively investigated by traditional solid state sintering method. Phase structures and morphology were detected by the X-ray diffraction and SEM, respectively. The electric field strength dependence of polarization was measured and employed to calculate the energy storage density. The doped SCT ceramics exhibit high permittivity, low loss, and higher breakdown strength. At 333 kV/cm electric field strength, the energy storage density of the 2 mol % Ca-doped SrTiO3 ceramics with fine grain can achieve 1.95 J/cm3, which is 2.8 times of pure SrTiO3 in the literature, and its energy storage efficiency reaches 72.3 %. Therefore, the SCT ceramics might be a kind of promising energy storage dielectric material.

The effect of SiO2 addition on phase transition, microstructure and microwave dielectric properties of α-CaSiO3 ceramics was reported for the first time. The X-ray diffraction analysis confirmed that the phase transformation from cyclo-CaSiO3 to pseudo-CaSiO3 was inhibited with the increase of SiO2 content. It was observed that the average grain size decreased with the increasing addition of SiO2 by scanning electron microscope. The τ f of the SiO2-added α-CaSiO3 ceramics almost remained constant with the SiO2 content increased, while the e r and Q × f changed obviously. The optimized properties were determined for SiO2 6 wt% additive α-CaSiO3 ceramics sintered at 1,350 °C: e r = 7.37, Q × f = 33,714 GHz and τ f = −11.08 ppm/°C.

The effects of Al2O3 additives on the sintering behavior, microstructures, and microwave dielectric properties of α-CaSiO3 ceramics have been investigated. The X-ray diffraction analysis indicated that the crystal phase of α-CaSiO3–Al2O3 ceramics was α-CaSiO3 with trace amounts of Ca2Al2SiO7, which could inhibit the growth of α-CaSiO3 grains by surrounding their boundaries and also improve the bulk density of α-CaSiO3–Al2O3 ceramics. However, excessive additives (≥3 wt%) of Al2O3 undermined the microwave dielectric properties of α-CaSiO3–Al2O3 ceramics because of the poor quality factor of Ca2Al2SiO7. The optimal Al2O3 addition was found to be 2 wt%, and the α-CaSiO3-2 wt%Al2O3 ceramic sintered at 1,250 °C showed excellent microwave dielectric properties with an e r of 7.39, a quality factor Q × f of 39,523 GHz and a τ f of −13.28 ppm/°C.

Development of high-temperature piezoelectric sensors is of great interest for harsh environment applications. The principal challenge for piezoelectric materials is their limitation for upper working temperature due to low Curie temperature and increasing conductivity at high temperatures. The effects of SiO2 addition on the microstructure, ferro-piezoelectric and thermal stability of 0.8BiFeO3–0.2BaTiO3 lead-free piezoelectric ceramics were investigated. XRD results indicated all the samples crystallized into the rhombohedrally distorted perovskite structure which was independent of the SiO2 addition. SiO2 could obviously inhibit the grain growth possibly due to the accumulation of SiO2 at the grain boundary. The leakage currents of 0.8BiFeO3–0.2BaTiO3 piezoceramics were remarkably reduced by certain amounts of added SiO2, facilitating the poling process, and improved their piezoelectric properties effectively. The optimal properties were obtained at the composition with 0.15 wt% SiO2 addition which retained high transition temperature ~628 °C. The samples sintered in O2 exhibited better thermal stability than those sintered in reduced atmospheres. Thus, SiO2 proved to be a successful additive to improve the 0.8BiFeO3–0.2BaTiO3 piezoceramics for high-temperature applications, as a result of increased resistivity and enhanced piezoelectric activity.

In current work, the effect of sintering atmospheres (N2, air and O2) on the structure, electrical properties, and defect mechanism of 0.8BiFeO3–0.2BaTiO3 lead-free piezoelectric ceramics has been investigated. X-ray diffractometer results indicated all the samples crystallized into the rhombohedrally distorted perovskite structure which was independent on the sintering atmospheres. Bi-containing impurity phases were observed in N2 sintered samples while not appearing in other atmospheres. X-ray photoelectron spectrum analysis indicated more Fe2+ ions, which can result in high leakage current, were involved in N2 sintered ceramics than that in O2- and air sintered compositions. However, greatly reduced leakage currents were obtained in N2 sintered ceramics which should be ascribed to the formation of secondary phases. The largest polarization and lowest leakage current were obtained in the sample sintered in N2 (2 h), which owned the optimal ferroelectric, piezoelectric, and electromechanical properties with piezoelectric constant d 33 = 98 pC/N, planar electromechanical coupling factors k p = 26.1 %, remnant polarization P r = 25.7 µC/cm2, coercive field E c = 74.6 kV/cm, and a high Curie temperature T c = 632 °C, respectively.

The effects of TiO2 addition on the densification, microstructure and microwave dielectric properties of pseudo-wollastonite ceramics (α-CaSiO3) have been investigated. The X-ray diffraction (XRD) patterns results indicate that samples exhibit a two-phase system, which has a wollastonite-structured α-CaSiO3 primary phase associated with a CaTiSiO5 minor phase. However, the TiO2 addition undermines the microwave dielectric properties because of the poor quality factor of the secondary phase of CaTiSiO5, which can inhibit the growth of α-CaSiO3 grains by surrounding their boundaries. The α-CaSiO3 ceramics containing 2 wt% of TiO2 sintered at 1,300 °C showed excellent microwave dielectric properties: an e r value of 7.86, a quality factor Q × f value of 16,491 GHz, and a τ f value of 0.76 ppm/ °C.

Sr1–1.5xSmxTiO3 (x = 0–0.025) ceramics were fabricated by the conventional solid-state reaction method. Experimental results show that all ceramics are pure cubic perovskite structure, and the lattice parameters and average grain sizes of the ceramics decrease with the Sm concentration increasing. Compared with the pure SrTiO3 ceramics, the relative dielectric constant could be enhanced to 3,681 (at 1 kHz and room temperature)with dielectric loss less than 0.02 when x = 0.02. The good stability of e r under 0–20 kV/cm is beneficial to applying in high voltage conditions. Two sets of relaxation peaks of Sm doped SrTiO3 ceramics are observed which are all related to the oxygen vacancies. The medium-temperature relaxation is ascribed to the coupling of oxygen vacancies with strontium vacancies and the origin of high-temperature relaxation is the motion of oxygen vacancies.

In this paper, boron suboxide fibres are synthesized by a solid state reaction method using CaO, B and Fe3O4 as starting materials in Ar atmosphere. The boron suboxide fibres include nanobelts and nanowires and they have unique morphologies. Through adjusting the contents of starting materials, we can control the diameters of boron suboxide fibres. Using the laser Raman spectrum, the photic properties were measured. The possible growth mechanism of the boron suboxide structure is discussed. As the boron suboxide has many excellent physics properties, it is believed that boron suboxide fibres synthesized have promising applications in functional ceramics fillings or in electronics.

LiNi0.80Co0.20− x Al x O2 samples (x = 0.025, 0.050 and 0.100) were prepared by a solid-state reaction at 725∘C for 24 h from LiOH⋅H2O, Ni2O3, Co2O3 and Al(OH)3 under oxygen flow. LiNiO2 simultaneously doped by Co-Al has been tried to improve the cathode performance. The results showed that substitution of optimum amount Al and Co at the Ni-site in LiNiO2 improved cycling performance. As a consequence, LiNi0.80Co0.15Al0.05O2 has 178.2 mAh/g of the first discharge capacity and 174.0 mAh/g after 10 cycles. Differential capacity vs. voltage curves indicated that the Co-Al co-doped LiNiO2 showed suppression of the phase transitions compared with pure LiNiO2.

The influence of TiCl3 solution on the room temperature (r.t.) resistivity and electrical properties of Ba0.92Ca0.08TiO3 PTCR ceramics was studied. The results indicate that the PTC effect can be improved significantly when an appropriate amount of TiCl3 in solution is added to the original materials. Some of the doped Ti3+ ions segregate at grain boundaries behaving as acceptors by substituting for Ti site or valence varying (from Ti3+ to Ti4+). As a result, the surface charge density Ns) increases and the barrier height at grain boundaries (φ) is enhanced.

The structure and properties of Mg-doped SrBi4Ti4O15(SBT) were dicussed. Mg substitution into SBT had two possibilities states with the dopant amount variety. Mg cation substituted mostly into Sr2+ and the amount proportion was 68.11%. Mg ion will substitute into Ti ion site in perovskite layer when the doping amount increases. Polarization increases sharply when x=0.1 and then decreases becauses of the domain pinning. The Curie temperature of Mg-doped SBT is about 300 °C and there is a broad diffuse phase transition near Tc with a flat peak near the Ta of SBT.

The effects of glass frit on the sintering and electric properties of PMN-PT textured ceramics were investigated. The glass frits, including PbO, Bi2O3 and ZnO, were selected since liquid phase sintering lowered the PMN-PT sintering temperature. The piezoelectric properties of PMN-PT ceramics with glass frit addition are strongly dependent on the densification. The addition of glass frits into PMN-PT matrix reduced the sintering temperature to 1 100 °C instead of 1 150 °C for samples without glass. The piezoelectric coefficients (d 33) of PMN-PT textured ceramics achieved 568 pc/N with 1 wt% excess PbO.