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With the continuous development of electronic devices, miniaturization and high capacitance have become important factors in the fabrication of multilayer ceramic capacitors (MLCCs) with a Ni internal electrode (Ni-MLCCs). The typical thickness of the dielectric layer of commercial MLCCs is less than 1 μm, which implies a higher capacitance compared to MLCCs with a thicker dielectric layer. In this study, 1210-type Ni-MLCCs were prepared via a tape casting method using a BaTiO 3 powder chemically coated with Dy and Ho additives. The high capacitance (390 nF) Ni-MLCC sintered at 1220 °C exhibited a low dielectric loss (tan δ < 2%), high insulation resistance (>9000 MΩ), and temperature stability comparable to that of the EIA X5R standard (capacitance-temperature coefficient (TCC) = ΔC/C 25 °C ≤ ±15%, between -55–85 °C). Relaxation behavior was observed between 1 Hz and 10 kHz, following the modified Curie–Weiss law and the Vogel–Fulcher relationship. The capacitive temperature stability of Ni-MLCC is closely related to the applied direct current (DC) bias field. The EIA X7R stability (TCC ≤ ±15%, between -55–125 °C) of the Ni-MLCCs at 1220 °C was gained under dc-bias field 3 and 5 V/μm. The capacitance varied as alternating current (AC) electric fields were applied. The grain shell was sensitive to both the DC bias and AC fields, but the grain core was more sensitive to the DC bias electrical field than the AC field. Furthermore, the ferroelectric response in MLCC decreases with rising temperature. [ABSTRACT FROM AUTHOR]

Abstract: Perovskite-structured Pb0.6Bi0.4(Ti0.75Zn0.15Fe0.1)O3 ceramics was reported with high Curie temperature T C of 705°C and tetragonality of c/a =1.10, promising for high temperature applications with large piezoelectric anisotropy. In this paper, it was experimentally demonstrated to ease poling processing and enhance piezoelectricity through substituting lead with calcium of Pb0.6−x Ca x Bi0.4(Ti0.75Zn0.15Fe0.1)O3. For the x =0.18 sample, electromechanical coupling factor ratio of k t /k p →∞, dielectric constant of 380, piezoelectric coefficient d 33 of 80pC/N, mechanical quality factor Q m of 50 and Curie point T C of 237°C were obtained, which exhibits better piezoelectric performance than the (Pb0.76Ca0.24)(Ti0.96(Co0.5W0.5)0.04)O3. The enhanced piezoelectric response was analyzed with relation to the reduction of tetragonality and Curie temperature. [Copyright &y& Elsevier]

With the increasing demand for the miniaturization, high capacitance and high reliability of the Multilayer Ceramic Capacitor (MLCC), the thickness of single dielectric layer is less than 1 μm and the original partical size of the powder has reached the scale less than 300 nm. In this paper, BaTiO 3 powder of various partical sizes (150–500 nm) was modified with Dy and Ho through a chemical coating method. The dense and uniform ceramics in accordance with EIA X7R-type temperature stability were sintered under low oxygen partial pressure and good dielectric properties of dielectric constant >2000 and dielectric loss <1% were obtained. The grain size effect on the dielectric properties under various dc-bias field were systematically investigated. It is found that the fine-grain ceramic exhibits a lower absolute change of the dielectric constant and a higher dc-bias stability. Furthermore, the modified 150 nm BaTiO 3 powders was made into 1210-type MLCCs, and the dielectric behavior of the MLCCs with different dc-fields and ac-fields were study over −55 °C–125 °C. It is found that the ac electric field had a greater influence on the dielectric properties at room temperature and below, and the dielectric constant variation under a dc-bias field was also greatly advanced for the modified fine-grain MLCCs. The results provide a reference for the design of the next generation of BME-MLCCs. [ABSTRACT FROM AUTHOR]

In this work, TiO 2 nanowire arrays embedded in PbZrO 3 -based antiferroelectric (AFE) films were fabricated on FTO/glass substrates using a facile two-step method. The energy storage performance was modulated by changing the density and morphology of TiO 2 nanowire arrays. A large recoverable energy density (W re) of 50.6 J/cm3 and efficiency (η) of 61% were achieved, which was attributed to the enhancement of maximum polarization and breakdown strength by constructing TiO 2 nanowire arrays in AFE films. More importantly, the composite films exhibited excellent thermal stability with the variation of energy storage density (<5%) and efficiency (<7%) in a wide temperature range (−120 to 130 °C) at the operating electric field of 1300 kV/cm. The results demonstrate that the composite films have huge potential in the future energy storage applications, whether in cold polar regions or high temperature regions. [ABSTRACT FROM AUTHOR]

The nonlinear dielectric responses of both unpoled and poled Mn-doped PMS-PZT ceramics as a function of hydrostatic pressure were investigated. Based on the application of Rayleigh law analysis, the contribution of irreversible domain wall motion to the dielectric response under hydrostatic pressure was quantitatively evaluated. Initial increased irreversible extrinsic contribution to the dielectric responses were observed in both unpoled and poled samples which can be ascribed to the pressure induced domain wall pinning relaxation effect. In addition, the pressure induced depolarization effect may also facilitate domain related extrinsic contribution to dielectric response in poled samples. The present study may shed further light on understanding the domain wall motion dynamic in piezoelectric ceramics under the application of hydrostatic pressure and is quite helpful for the design and optimization of piezoelectric devices used in underwater areas. [ABSTRACT FROM AUTHOR]

The Al 2 O 3 -modified Pb 0.99 (Zr 0.95 Ti 0.05 ) 0.98 Nb 0.02 O 3 (PZT 95/5) ferroelectric ceramics with enhanced breakdown strength were prepared from PZT 95/5 powders coated with a thin Al 2 O 3 shell layer, which were fabricated by a Citrate-Chelation method followed by a conventional sintering process. The microstructure and electrical properties of the as-prepared ceramics as a function of Al 2 O 3 content were systematically investigated. The results reveal that Al 2 O 3 nanoparticles are successfully coated on PZT 95/5 powders to form the core–shell structure and well dispersed at the grain boundaries of the PZT 95/5 ceramic matrix after sintering, which strengthened the grain boundaries. In particular, compared with pure PZT 95/5 ferroelectric ceramics, PZT 95/5 ceramics with less than 1.0 wt% Al 2 O 3 inclusion possess the enhanced breakdown strength and energy density, of which the largest increment being 25.9% and 13.5%, respectively. It is indicated that the as-prepared PZT 95/5 ferroelectric ceramics may be a promising candidate for explosively driven power supply. [ABSTRACT FROM AUTHOR]

Abstract: Dielectric properties of Pb0.99375(Zr0.52Ti0.48)0.9875Nb0.0125O3 (PZTN) ceramics were measured during heating and cooling processes before and after poling. A dielectric anomaly from 220K to 290K was only observed in poled PZTN samples. The frequency dependence of the ε′′ peaks was fitted using the Vogel–Fulcher law, which indicated that this dielectric anomaly could be associated with the poling induced monoclinic distortion. Meanwhile, the existence of the low-temperature transformation involving rotations of the octahedra was confirmed by the broadening peaks in ε′′–T curves and the variation of slopes in ε′–T curves in both unpoled and poled samples. [Copyright &y& Elsevier]

Abstract: Porous Pb (Zr0.95Ti0.05) O3/xMgO (PZT/MgO, x=0, 0.1, 0.2, 0.5 and 1.0wt%) ferroelectric ceramics were prepared with MgO nanoparticles as reinforcing phase. The effects of MgO nanoparticles on the phase, microstructure, electrical and mechanical properties of as-prepared ceramics were investigated. The results show that the grain size is reduced obviously when increasing the amount of MgO. Compared with pure porous PZT, T C of MgO-added PZT ceramics shifts to higher temperature. Moreover, dielectric, ferroelectric and piezoelectric properties show no much degradation. Further, PZT/MgO ceramics possess enhanced mechanical properties compared to pure porous PZT ceramics, the largest increment of the fracture toughness and hardness being 31.3% and 19.8%, respectively. The optimal electrical and mechanical properties are obtained with the addition of less than 0.5wt% MgO nanoparticles. [Copyright &y& Elsevier]

Abstract: Sr x Ba1−x Nb2O6 (with x=0.50, 0.45, 0.40 and 0.30) ceramics were synthesized by conventional solid-state method and sintered at 1350°C for 3h. The phase structure, microstructure, dielectric, ferroelectric and pyroelectric properties of obtained ceramics were systematically investigated. Pure tungsten bronze phase could be obtained in all ceramics. The dielectric characteristics showed that SBN ceramic was a relaxor with strong diffuse phase transition and weak frequency dispersion. As Sr molar fraction x increases from 0.30 to 0.50, the transition temperature T C decreased linearly while the diffusivity parameter γ declined from 1.88 to 1.68. The saturated polarization, remnant polarization and pyroelectric coefficient were also found to be enhanced in SBN ceramics with increasing Sr content. The pyroelectric coefficient of about 2×10−8 C/cm2K can be obtained for polarized SBN50 ceramics at room temperature. [Copyright &y& Elsevier]

Abstract: Ba0.6Sr0.4TiO3 (BST)/MgO columnar composites are fabricated via the spark plasma sintering (SPS) method. The microstructure, dielectric and tunable properties of columnar composites are investigated. The unmodified BST Curie temperatures with the increase of MgO addition indicate a sufficient suppression of ions interdiffusion between the two phases. The dielectric constant is decreased from 7000 to 3800 when MgO weight ratio is up to 15% while the tunability still stays at high level over 45%. The coefficient of the dielectric nonlinearity β shows a growing trend with increasing MgO content. The experimental results are in agreement with the theoretical prediction and confirm that if the composite is fabricated in columnar model, a reduction of dielectric constant without a deterioration of tunability could be achieved, which make them useful for potential tunable device applications in wireless communication system. [Copyright &y& Elsevier]

Abstract: A simple process has been investigated to synthesize nanocrystalline Ba0.70Sr0.30TiO3 (BST) powders via a nonhydrolytic sol–gel method by using barium acetate, strontium acetate, titanium tetrabutoxide, ethanol, acetic acid and acetylacetone as the starting materials. Thermogravimetry (TG) and differential thermal analysis (DTA) were used to examine the decomposition behaviour of the xerogel. The particle size of BST is close to 30nm calculated by X-ray diffraction (XRD) and confirmed by transmission electron microscopy (TEM). Using these nanocrystalline BST powders, dense BST ceramics with ultrafine grains were obtained by spark plasma sintering (SPS). The grain size effect on the dielectric properties was studied. It was shown that as the grain size decreased, the transition temperature (T c) and the dielectric constant decreased and the transition became diffuse. [Copyright &y& Elsevier]

Abstract: Ba(Zr x Ti1−x )O3 (BZT) (x =0.25, 0. 3, 0.35, 0.4) ceramics were prepared by the traditional ceramic processing and their structural, surface morphological, dielectric properties, tunable properties as well as the mechanism of their nonlinear dielectric constant under DC electric field were systemically examined. The Zr ions substitution of Ti ions has a strong effect on the dielectric properties and the grain sizes. The results show Ba(Zr x Ti1−x )O3 (x =0.25, 0.3, 0.35) ceramics to be promising candidates for the DC electric field tunable materials for microwave electronics application, because they exhibit high tunability (27.6%, 26.3%, 19.4%, respectively) as the strength of electric field is up to 2kV/mm, low dielectric loss (0.001–0.002, 0.001–0.002, 0.004–0.005, respectively) at 10kHz at room temperature and low temperature coefficient of capacitance. [Copyright &y& Elsevier]

Abstract: Acceptor (Mn-, Co-) doped and donor Y-doped Ba0.6Sr0.4TiO3 have been prepared by traditional ceramic processing and their structural, surface morphological, dielectric and tunable properties were investigated. The results show all dopants to have a strong effect on the average grain size. The curie temperature of all doped specimens decreases and their temperature spectrum broadens. Loss tangent at 15°C and low frequency (10kHz) increases for all doped specimens whereas the loss tangent at high frequency (100MHz) is not affected. The tunability of all the doped specimens is lower than the undoped one. [Copyright &y& Elsevier]

(1− x )(Ba,Sr)TiO 3 – x ZnAl 2 O 4 ( x =0.00, 0.05, 0.10 and 0.20) composites were prepared by the traditional solid state reaction. The dielectric, tunable and Raman spectroscopy properties are studied. The curie temperature of the composites does not show much difference due to low solubility between BST and ZnAl 2 O 4 . For the composition with x =0.20, its tunability is up to 46.4% (@2 kV/mm), nearly 1.5 times of that of pure BST, and meanwhile its dielectric constant and loss are decreased. The results imply that making non- or little-soluble BST-nonferroelectric composites is a very effective way to keep high tunability and low dielectric constant simultaneously. Raman results confirm that there are some residual polar microregions in (1− x )BST– x ZnAl 2 O 4 composite, and their extrinsic contribution to the dielectric tunability is responsible for a deviation from the ε versus E behavior predicted by Johnson׳s equation. [ABSTRACT FROM AUTHOR]