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The crystallographic structure, dielectric, impedance and piezoelectric properties of novel (0.67 − x)BiFeO3–0.33BaTiO3–x(Na0.5La0.5)TiO3 (NLT100x, x = 0.0, 0.02, 0.04, 0.06, 0.08) ceramics were systematically investigated experimentally. The crystallographic studies showed that different concentrations (Na0.5La0.5)TiO3 doping were well soluble with the BiFeO3 system to form a single pseudo-cubic phase solid solution. The dielectric analysis shows that the doping reduces the leakage current, suppresses the Bi volatilization, expands the dielectric peak, and leads to the evolution of relaxor behavior. Moreover, the large strain (S) of 0.255% and the normalized strain of 430 pm/V were obtained at x = 0.04 and 60 kV/cm, which is attributed to the coexistence of ferroelectric and relaxor domains favoring the domain steering. More importantly, raising the temperature can further improve the strain performance, reaching the maximum strain (Smax) value (~ 0.346%) with the maximum normalized strain of (~ 714 pm/V) at 120 °C and 50 kV/cm. The results show the potential value of the ceramics in piezoelectric actuator applications. [ABSTRACT FROM AUTHOR]

Sr 2-2 x Ca 2 x CeO 4 (x = 0, 0.025, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8) ceramics were synthesized through cold isostatic pressing and solid-state reaction. The microstructure, defects, microwave dielectric properties, and the effect of Ca2+ doping of Sr 2 CeO 4 ceramics were systematically investigated. As the sintering temperature increased, the densities of Sr 2 CeO 4 ceramics rose, the content of oxygen vacancies increased, and Ce4+ reduction would be enhanced. In addition, the Sr 2 CeO 4 structure had poor compatibility with Ca2+. The major phase could be kept unchanged only when x ≤ 0.1. The reason was that the doping of Ca2+ intensified the distortion of the CeO 6 octahedron and induced the structural transformation of the common edges (Sr 2 CeO 4) to the common angles (SrCeO 3). With the increase of dopant, the densities of Sr 2-2 x Ca 2 x CeO 4 ceramics increased significantly, while the content of oxygen vacancies also increased. The microwave dielectric properties were mainly influenced by the density, structural symmetry, defects, and the second phase SrCeO 3. The dielectric permittivity (ε r) of 13.4–15, the quality factor (Qf) of 118,580–52,170 GHz, and the temperature coefficient of resonant frequency (τ f) of −58.3 ∼ −47.5 ppm/°C were obtained for Sr 2-2 x Ca 2 x CeO 4 ceramics When x ≤ 0.1. This work has provided a foundation for further research on cerate microwave dielectric ceramics. [ABSTRACT FROM AUTHOR]

(Bi0.5Na0.5)0.94Ba0.06Ti1−x(Y0.5Nb0.5)xO3 (abbreviated as BNTBT-100xYN) lead-free relaxor ceramics were designed and prepared using a traditional solid-state sintering technique. The influences of the introduction of (Y0.5Nb0.5)4+ complex ions for the dielectric properties and energy storage performances of BNTBT-100xYN ceramics were systematically studied. All samples exhibited a typical pseudo-cubic symmetry structure and obtained the dense microstructure with the uniform distribution of all elements. The ergodic relaxor behavior of all ceramics was observed and revealed a trend of increase as a function of composition. It accelerated the improvement of the temperature stability of the dielectric constant. All samples showed a single grain conduction mechanism and the activation energy decreased with the addition of composition. It is related to the generation of oxygen vacancies induced by the defect dipoles. BNTBT-6YN ceramic revealed excellent dielectric temperature stability within the temperature range from 87 to 479 °C and the loss tangent less than 0.05 between 25 °C and 474 °C. Besides, a high recoverable energy density of ~ 0.91 J/cm3 with the corresponding efficiency of ~ 78.5% at applied 115 kV/cm field was achieved for BNTBT-5YN ceramic. Hence, BNTBT-5YN and BNTBT-6YN ceramics will become one of the outstanding dielectric ceramics for the electronic components. [ABSTRACT FROM AUTHOR]

Polycrystalline Ba(1−x)(La0.50Li0.50)xTiO3 (0 ≤ x ≤ 0.12) ceramics are fabricated via the solid-state reaction technique to analyze their structure, excellent dielectric permittivity, and ferro/piezoelectric characteristics systematically. Powder x-ray diffraction has revealed the pure polycrystalline tetragonal symmetry for x ≤ 0.09 compositions. Rietveld refinement analysis has revealed the structure having a reducing tetragonality with increasing composition. A dense and compact ceramic with many grains having different size distributions has been perceived. The substitution of Li and La ions in BaTiO3 unit cell lattice has increased the ambient temperature dielectric permittivity with reduced loss tangent from ~ 2000, ~ 0.019 (for x = 0) to ~ 5166, ~ 0.002 (for x = 0.09) at 1 MHz frequency. In addition, a high bipolar strain ~ 0.24% for x = 0.03 is obtained. The increase of dielectric permittivity with reduced loss tangent might be applicable for capacitor applications at ambient conditions. [ABSTRACT FROM AUTHOR]

A series of Bi 0.5- x Er x Na 0.4 K 0.1 TiO 3 (BNKT- x Er) ceramics were designed and fabricated, the dopant effects on dielectric, piezoelectric and photoluminescence properties were studied. The results show that the piezoelectric property of BNKT can be enhanced by a trace amount of Er dopant, which is also reflected in the large linear electrostrain (S uni = 0.29%, under 55 kV/cm) achieved in BNKT-0.0025 Er. On the other hand, higher Er content can produce excellent dielectric temperature stability, with △ ԑ / ԑ 150 °C < ±15% over temperature range of 90∼510 °C. Meanwhile, all BNKT- x Er ceramics exhibit good photoluminescence properties, which may open new applications of these multifunctional ceramics. [ABSTRACT FROM AUTHOR]

• Three dielectric anomaly peaks were found in a two-layer BLSFs high temperature piezoelectric ceramic for the first time. • The contribution of each ion to the piezoelectric properties was analyzed by conclusion of Rietveld refinement. • (Y 0.5 Sb 0.5)4+-doped BTN ceramic have reduced oxygen vacancies and increased activation energy, resulting in enhanced ceramic performance at high temperature. Bismuth layered material stand out from other piezoelectric materials due to their high Curie temperature (T c) and are often used in high temperature piezoelectric actuators and capacitors. However, its low piezoelectric coefficient (d 33) and dielectric constants (ε′) limit the scope of application of this material. The Bi 3 Ti 0.99 (Y 0.5 Sb 0.5) 0.01 NbO 9 (BTN-1YSb) ceramics by solid state sintering method show improved d 33 (8.1 pC/N), dielectric constants (ε′ ∼2051), temperature stability (d 33 ＞8 pC/N at 800 °C) and mechanical quality factor (Q m ∼ 1834). After Rietveld refinement, it was found that the oxygen element contributed the most to the spontaneous polarization (P s) enhancement of the piezoelectric material. In addition, three dielectric anomalous peaks are observed for the first time in BTNO-4YSb BTN-3YSb ceramics, which is due to the interaction of point defects with domain walls in a wide temperature range. This advantage can be maximized by tuning the dielectric anomaly peak to provide a more stable d 33 at high temperatures. This study analyzes that the contribution of each ion to the piezoelectric properties of BTN-based ceramics and provides a good example for the study of dielectric peaks. [ABSTRACT FROM AUTHOR]

The 0.65Bi0.5Na0.25K0.25TiO3–0.35Bi0.2Sr0.7Ti1−xSnxO3 (BNKBST-xSn) ceramics were synthesized via a solid-phase reactive sintering technique. The effects of doping Sn4+ ions on the energy storage, dielectric, ferroelectric properties and microstructure characteristics for BNKBST ceramics were systematically studied. Remarkably, BNKBST-0.02Sn exhibits a superior dielectric temperature stability, manifested as the change rate for dielectric constant ∆ε/ε150°C is smaller than 15% during a very wide temperature range of 30–400 °C. In addition, BNKBST-0.02Sn ceramic achieves a high energy storage density Wrec = 0.81 J/cm3 (under the electric field 80 kV/cm) with an outstanding energy storage efficiency 89.5%, which make it reasonable to be applied in dielectric capacitors due to its excellent dielectric thermal stability and energy storage properties. The electrical conductivity behaviors of BNKBST-xSn were also analyzed with the assistance of impedance spectroscopy. [ABSTRACT FROM AUTHOR]

0.94(Bi 0.5 Na 0.5)(Y 0.5 Ta 0.5) x Ti 1- x O 3 -0.06BaTiO 3 lead-free piezoelectric ceramics were prepared by a conventional solid-state reaction method to study their excellent electro-strain properties and energy storage characteristics systematically. All ceramics exhibited a dense surface morphology. The introduction of (Y 0.5 Ta 0.5)4+ complex ions destroyed the long-range ferroelectric order, which reduced the T F-R to the operating temperature, resulting in an easier field-induced transition between relaxor and ferroelectric phase. Therefore, for x = 0.01 component attained unipolar strain of 0.37% under 52 kV/cm, and the corresponding normalized strain d 33 * was 708 pm/V. Besides, the destruction of the ferroelectric phase also induced a pinched hysteresis loop and the maximum storage density of 1.215 J/cm3 with the efficiency of 68.7% obtained at 98 kV/cm for BNYT30 ceramics. These all demonstrated that the doping of complex ions (Y 0.5 Ta 0.5)4+ made the BNT-BT an outstanding candidate for actuators and energy storage devices. [ABSTRACT FROM AUTHOR]

Low frequency dielectric dispersion behavior of the indium doped cadmium zinc telluride single crystal has been investigated. The temperature dependent of dielectric loss shows a broadening peak at high temperatures, which is attributed to thermally activated relaxation process. The large dielectric permittivity can be attributed to the influence of the dc conductivity and the predominance of the dc conduction in low frequency region overshadows the true behavior of the imaginary part of dielectric permittivity. The contribution of dc conduction and ac conduction has also been studied. A polaron theory indicates that the dielectric relaxation of the indium doped cadmium zinc telluride crystal at high temperature is associated with the hopping localized cadmium vacancies and telluride antisites defects. The hopping energy increases from 1.204 eV at 499 K to 1.267 eV at 534 K monotonically, which is close to the thermal activation energy 1.541 eV and dc conductivity activation energy 1.239 eV. [ABSTRACT FROM AUTHOR]

The temperature dependence of dielectric permittivity was investigated for the barium zirconium titanate solid solution system [BZT, Ba(ZrxTi1-x)O3 0.25≤x≤0.5]. The dielectric relaxation behavior was observed in these ferroelectrics with diffused phase transition. In contrast to the canonical relaxors such as Pb(Mg1/3Nb2/3)O3, the diffused phase transition of BZT could not be well described by the popular modified Curie–Weiss law. Quasiferroelectric state theory was introduced to explain the dielectric results of the BZT relaxors. [ABSTRACT FROM AUTHOR]

The high temperature capacitors operated in some harsh conditions require dielectric ceramics with stable permittivity, low dielectric loss and high resistivity to temperatures above 200 °C. In this work, high temperature dielectrics based on (1-x-y)Bi 0.5 Na 0.5 TiO 3 -xBiAlO 3 -yK 0.5 Na 0.5 NbO 3 ceramics were designed and prepared. The introduction of BiAlO 3 leads to the reduction of dielectric loss due to the formation of defect dipoles. And the introduction of K 0.5 Na 0.5 NbO 3 leads to the disruption of long-range ferroelectric order, which is helpful to increase the temperature stability of permittivity. The composition of x = 0.07 and y = 0.05 has a stable permittivity between 86.5 °C and 324.5 °C and dielectric loss below 0.02 in the temperature range of 110 °C–336 °C. Therefore, this system will be one of promising candidates of dielectrics used for high-temperature capacitors. [ABSTRACT FROM AUTHOR]

Magnesium titanate stannate - calcium strontium titanate (MgTi 0.95 Sn 0.05 O 3 - x Ca 0.8 Sr 0.2 TiO 3 ; abbreviated as MTS- x CST, x = 0.02, 0.04, 0.06, 0.08) microwave dielectric ceramics were synthesized via the conventional solid-state reaction. The optimum densities corresponded to higher sintering temperatures than the optimum quality factor, so the ceramics were classified as MTS- x CST-D and MTS- x CST-Q. All compositions exhibited a composite phase consisting of the rhombohedral structure MTS and the orthorhombic structure CST. As the sintering temperature rose, the relative densities of the ceramics increased significantly, while the formation of oxygen vacancies and titanium reduction were intensified. Finally, the x = 0.06 compositions sintered at 1425 °C (MTS-0.06CST-D) and 1375 °C (MTS-0.06CST-Q) had excellent temperature stability and low loss. At low frequency, the change of dielectric permittivity at 25–150 °C did not exceed 0.1, and the loss tangent was less than 0.003. In addition, microwave dielectric properties of MTS-0.06CST-D (ε r = 20.4, Qf = 63,770 GHz, τ f = −1.8 ppm/°C) and MTS-0.06CST-Q (ε r = 18.4, Qf = 74,740 GHz, τ f = −4.3 ppm/°C) compositions were obtained. These results suggest that MST-0.6CST ceramics could be a candidate material for 5 G microwave communication devices. • MgTi 0.95 Sn 0.05 O 3 - x Ca 0.8 Sr 0.2 TiO 3 were synthesized via the conventional solid-state reaction. • The sintered ceramics only kept MgTi 0.95 Sn 0.05 O 3 rhombohedral phase and Ca 0.8 Sr 0.2 TiO 3 orthorhombic phase. • Oxygen vacancies and titanium reduction after high temperatures sintering were investigated. • Excellent microwave dielectric properties of ε r = 20.4, Qf = 63,770 GHz, τ f = −1.8 ppm/°C and ε r = 18.4, Qf = 74,740 GHz, τ f = −4.3 ppm/°C were obtained. [ABSTRACT FROM AUTHOR]

The electric and dielectric properties of (Bi 0.5− y Na 0.5 ) 0.94− x Ba 0.06 (Bi 0.2 Sr 0.7 □ 0.1 ) x TiO 3 (BNBT–BST) ceramics, derived from the morphotropic phase boundary (MPB) of the parent matrix 0.94(Bi 0.5 Na 0.5 )TiO 3 –0.06BaTiO 3 (BNT–BT), are studied. The pseudocubic structures are formed without apparent secondary phases for all the compositions. The Bi deficiency displays significant effect on the dielectric permittivity of BNBT–BST ceramics. A plateau of high permittivity ∼5000 in the temperature evolution is formed with small variation, indicating the potential use for the high-temperature dielectrics. The bulk conductivity, calculated from the complex impendence ( Z ′/ Z ″), is conducted to learn the influence of the oxygen vacancies on the dielectric response in different atmospheres. After the re-oxidation of the Bi deficient BNBT–BST ceramics, the operational temperature range is broadened with 10% variation in permittivity from 50 °C to 300 °C. [ABSTRACT FROM AUTHOR]

• Discussing the effects on the structures of (1- x)Ca 0.8 Sr 0.2 TiO 3 - x SmAlO 3 ceramics with the content of SmAlO 3. • Observing excellent temperature stability of dielectric permittivity and low dielectric loss at low frequencies. • Discovering a high-performance microwave dielectric ceramics with ε r = 42.0, Qf = 39,120 GHz, and τ f =-6.4 ppm/℃. (1- x)Ca 0.8 Sr 0.2 TiO 3 - x SmAlO 3 (abbreviated as (1- x)CST- x SA) perovskite ceramics were synthesized through the conventional solid-state reaction process. The effects of SmAlO 3 on the microstructure, low-frequency dielectric performances, and microwave dielectric properties for (1- x)CST- x SA ceramics were investigated systematically. All compositions exhibited an orthorhombic perovskite structure with dense surface morphology. With increasing the content of SmAlO 3 , the order of B-site cation revealed a trend of increase first and then slowly decreased. The presence of oxygen vacancies in the (1- x)CST- x SA ceramics was detected by using x-ray photoelectron spectroscopy. Excellent temperature stability of dielectric permittivity and low dielectric loss (tan δ lower than 0.005) were observed for (1- x)CST- x SA ceramics at low frequencies. For x = 0.35 composition, the temperature coefficient of the resonant frequency approached zero. In addition, the dielectric permittivity of 42.0, the quality factor of 39,120 GHz, and the temperature coefficient of resonant frequency of − 6.4 ppm/℃ were obtained for 0.65CST-0.35SA ceramics. It is suggested that (1- x)CST- x SA ceramics can be used as a candidate material for various microwave communication components. [ABSTRACT FROM AUTHOR]

Highlights: [•] (1−x)Ba(Zr0.25Ti0.75)O3–xMgO thick films were prepared by tape-casting. [•] Dielectric tenability was 92.54~30.56% at 42kV/cm, room temperature and 1kHz. [•] High figure-of-merit, 103.97~219.86, of these films was attained. [•] Dielectric dispersion of these films was described by the Lorentz-type relation. [•] (ɛ (0) / ɛ(E) )3 vs. (E2) was fitted by the Johnson’s equation according to Devonshire’s theory. [ABSTRACT FROM AUTHOR]

Abstract: (K0.5Na0.5)(Nb1−2x/5Cu x )O3 (abbreviated as KNNC, x =0–2%) lead-free ceramics were synthetized by the solid state solution method. Pure perovskite phase with orthorhombic symmetry was observed. The evolution of the structure of KNNC was examined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman scattering spectra techniques. Our results revealed that, defect dipoles were formed and provided a restoring force to reverse the switched polarization, which resulted in double P–E hysteresis loops in KNNC with Cu doping at x =0.75% and 1%. However, non-polar defect complex caused a lattice shrinkage and the observed square shaped P–E loops in KNNC ceramics under high doping levels (x >1%). [Copyright &y& Elsevier]

Ba0.6Sr0.4(Ti1− xMg x)O3 (BSTM) ceramics were prepared by using a solid-state reaction process. X-ray diffraction results indicated that the solubility limit of Mg in Ba0.6Sr0.4TiO3 was about 3 mol%. Doping of Mg into BST led to diffused cubic-tetragonal ( C- T) phase transition and reduced Curie temperature. The diffused parameter γ obtained by fitting the modified Curie-Weiss laws increased with increasing Mg content. Dielectric properties of the BSTM ceramics were measured. Figure of merit of BSTM3 was up to 127.8 at 17.5 kV/cm. Its dielectric loss was as low as 0.00133 at 1 kHz and room temperature. [ABSTRACT FROM AUTHOR]

Abstract: Phase composition, microstructure and tunable dielectric properties of (1− x)BaZr0.25Ti0.75O3–xMgO (BZTM) composite ceramics fabricated by solid-state reaction were investigated. It was found Mg not only existed in the matrix as MgO, there was also trace amount of Mg2+ ions dissolved in the BZT grains, which led to Curie temperature of the BZTM composites ceramics shifting to below −100°C. Dielectric permittivity of the BZTM composite ceramics was reduced from thousands to hundreds by manipulating the content of MgO. Johnson''s phenomenological equation based on Devonshire''s theory was used to describe the nonlinear dielectric permittivity of the ceramics with increasing applied DC field. With increasing content of MgO, anharmonic constant α (T) increased monotonously. Dielectric permittivity was 672, while dielectric tunability was as high as 30.0% at 30kV/cm and dielectric loss was around 0.0016 for the 0.6BaZr0.25Ti0.75O3–0.4MgO sample at 10kHz and room temperature. [Copyright &y& Elsevier]

Sodium potassium niobate KNaNbO(KNN) ceramic was synthesized by a solid-state technique. The X-ray diffraction of the sample at room temperature showed a monoclinic phase. The real part ( ε′) and imaginary part ( ε″) of dielectric permittivity of the sample were measured in a frequency range from 40 Hz to 1 MHz and in a temperature range from 350 to 850 K. The ε′ deviated from Curie-Weiss law above 702 K, due to additional dielectric contributions resulting from universal dielectric response and thermally activated space charges at high temperatures. This anomaly arose from a Debye dielectric dispersion that slowed down following an Arrhenius law. We have established a link between the dielectric relaxation and the conductivity. [ABSTRACT FROM AUTHOR]

Piezoelectric thermal stability is often a critical issue for many piezoelectric materials in practical applications. Lead-free piezoelectric ceramics, (1−x)K0.5Na0.5NbO3– xAgNbO3 (KNN-AN, with x = 0–0.35) have been synthesized by a conventional solid state sintering method. The temperature dependence of the dielectric, ferroelectric and piezoelectric properties of lead-free piezoelectric ceramics was investigated. The piezoelectric properties exhibit a very good thermal stability up to high temperature, which is a significant improvement from other KNN-based piezoceramics. [ABSTRACT FROM PUBLISHER]

Abstract: A network microstructure with large grains isolated from one another by the regions constituted with the agglomerated fine grains of CCTO ceramics fabricated by sol–gel processing has been investigated. The temperature dependence of dielectric properties associated with the contribution of grain below 90°C, grain boundary in the temperature range of 90–250°C, and electrode interface above 250°C has been demonstrated under 10kHz from room temperature to 400°C and the presence of dielectric diffusion behavior above room temperature is clear. Also, the pyroelectric properties have been measured up to 250°C so as to eliminate the effect of electrode interface and the incidence of the pyroelectric effect associated with the temperature dependence of pyroelectric coefficient implies that CCTO has a vast potential in the field of high-temperature pyroelectric sensing without induced applied bias. [Copyright &y& Elsevier]

Abstract: Barium titanate–silver composites were prepared by using a solid state reaction process with silver contents ranging from 0mol% to 20mol%. XRD results and Raman spectra indicated that there was no phase other than BaTiO3 and Ag in the ceramics and tetragonality of barium titanate reduced with increasing Ag content. SEM images illustrated that Ag influenced densification and microstructure of BaTiO3 ceramics. Besides, addition of Ag led to increase in dielectric permittivity and broadening of ferroelectric–paraelectric phase transition peak. Also addition of Ag had effects on dielectric loss and dc conductivity. Dielectric and conductivity properties as a function of Ag volume fraction were explained by the percolation theory. [Copyright &y& Elsevier]

Abstract: The structural, electronic and optical properties of BiFeO3 (BFO) were investigated employing the first-principles within generalized gradient approximation (GGA). The magnetic moments were balanced out each other by the two irons spinning oppositely in a cell. The band gap of BFO was found to be 2.5eV by the electronic structure calculation. Analysis of the density of states indicated that the valence band was consisted with Fe-d and O-p states, and the conduction band was composed of Fe-d and Bi-p states. The dielectric function, absorption, refractive index, extinction coefficient, reflectivity and electron energy loss were calculated for radiation up to 31eV in order to understand optical properties of BFO. The reasons of the absorption were discussed. [ABSTRACT FROM AUTHOR]

Monodisperse (Ba0.6Sr0.4)TiO3 nanoparticles have been successfully synthesized by a liquid-solid-solution method at low temperature of 160°C. The purity dependence on the concentration of mineralizer has been investigated. Subsequently, the (Ba0.6Sr0.4)TiO3 thick film has been deposited on Pt/Ti/SiO2/Si substrates by an electrophoretic deposition method and capacitance verse voltage (C-V) as well as leakage current density versus electrical field (J-E) characteristics has been studied. The dielectric tunability of 82.6% can be obtained and the dominant leakage mechanism is Schottky emission for positive biases as the Pt bottom electrode negatively biased. [ABSTRACT FROM AUTHOR]

Abstract: Lead magnesium niobate–lead titanate (0.80Pb(Mg1/3Nb2/3)O3–0.20PbTiO3, PMN–PT) thick films on platinum metallic foils were successfully fabricated by electrophoretic deposition (EPD). The room temperature relative dielectric constant and the maximum relative dielectric constant were 4645 and 25,640 at 1kHz, respectively. The relaxor nature of PMN–PT thick films was studied in terms of diffused phase transition along with frequency dispersion of temperature of dielectric maximum (T m). Deviation from Curie–Weiss behavior and temperature evolution of the local order parameter were found in the films. The degree of relaxation obtained from the modified Curie–Weiss law strongly suggests the relaxor behavior. Vögel–Fulcher relationship was used to analyze the frequency dependence of temperature of dielectric maximum (T m). [Copyright &y& Elsevier]

Abstract: Ultrathin La2O3 gate dielectric films were prepared on Si substrate by ion assistant electron-beam evaporation. The growth processing, interfacial structure and electrical properties were investigated by various techniques. From XRD results, we found that the La2O3 films maintained the amorphous state up to a high annealing temperature of 900°C for 5min. From XPS results, we also discovered that the La atoms of the La2O3 films did not react with silicon substrate to form any La-compound at the interfacial layer. However, a SiO2 interfacial layer was formed by the diffusion of O atoms of the La2O3 films to the silicon substrate. From the atomic force microscopy image, we disclosed that the surface of the amorphous La2O3 film was very flat. Moreover, the La2O3 film showed a dielectric constant of 15.5 at 1MHz, and the leakage current density of the La2O3 film was 7.56×10−6 A/cm2 at a gate bias voltage of 1V. [Copyright &y& Elsevier]

Abstract: Pyrochlore free PbMg1/3Nb2/3O3 (PMN) thick films were prepared by using a hydrothermal process from oxide-based suspension precursors. PMN thick films have been grown on titanium substrates at 150°C for 8h. The effect of processing parameters such as reaction durations and mineralization conditions on perovskite phase formation on the microstructures is very critical. By controlling the operating parameters, high quality PMN thick films on titanium substrates were fabricated. The films with a single perovskite structure were smooth and the surfaces were free of micrometer scale cracks. The thickness of the film was about 20μm. Dielectric responses of the PMN films were characterized in detail. The samples showed excellent reproducibility in the measurement of dielectric responses. [Copyright &y& Elsevier]

Abstract: A model has been developed for the prediction of the dielectric property and the acoustic impedance of particle/polymer composite used in the plastic packaging of the shock-wave pulsed transducer. Expressions are derived for the parameters of the composite in terms of the volume fraction of particle and the polymer. The model is illustrated by analyzing composites made from Al2O3 particle and the epoxy resin, with the anisotropy of the Al2O3 taken into account. Comparisons with the rod and particle of Al2O3 are discussed. The three different polymers, polyethylene, epoxy resin and PVDF are also discussed. The model gives some physical insight into the design of the composites used in the transducer and shows good correlation between calculated and measured ultrasonic velocities. [Copyright &y& Elsevier]

Abstract: BaTiO3 nanopowders were attempted to synthesize by using a novel straight-forward, solvent free reactions under autogenic pressure at elevated temperature (RAPET) approach. The as-prepared BaTiO3 nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, high-resolution TEM, and convergent-beam electron diffraction. It was found that Ba(OH)2·8H2O and Ti(OBu)4 could be appropriate starting materials to synthesize BaTiO3 at 973K for 2h by using RAPET approach. Pure tetragonal BaTiO3 nanopowders could be obtained by exceeding moderate amount of Ba(OH)2·8H2O in the starting materials. The obtained BaTiO3 nanoparticles had well dispersion and crystallinity, possessed a tetragonal perovskite structure at room temperature and relatively narrow particle size distribution. [ABSTRACT FROM AUTHOR]

Abstract: Lead magnesium niobate–lead titanate (0.80Pb(Mg1/3Nb2/3)O3–0.20PbTiO3, PMN–PT) 16-μm thick films on platinum metallic foils were successfully fabricated by electrophoretic deposition (EPD). The EPD process was conducted in ethanol medium with pH 6.0. The effects of deposition parameters, such as deposition voltage and deposition time were evaluated. Single-phase PMN–PT thick-film structures without any pyrochlore phase were obtained after the sintering at 1100°C for 1h. Relaxor-like behaviour was clearly demonstrated in PMN–PT thick films. The room temperature relative dielectric constant and the maximum relative dielectric constant were 4800 and 26100 (at 1kHz), respectively, which are comparable to the reported values for bulk samples. [Copyright &y& Elsevier]

Abstract: Ba(Fe0.5Nb0.5)O3 (BFN) ceramics were synthesized by a traditional mixed oxide method (BFN-M), as well as a columbite method (BFN-C) with FeNbO4 precursor. X-ray diffraction reveals that both the ceramics and precursor have a pure monoclinic phase. BFN-C samples showed improved microstructure with less pores and smaller grain size. Dielectric properties of the BFN ceramic were characterized in a broad frequency range (0.1Hz to 10MHz) and a temperature range from −120 to 300°C. A Debye-like relaxation was found in a low-frequency range, where a high-temperature dielectric anomaly was observed too. The relative low-dielectric loss suggests that columbite method should be a better choice for the synthesis of A(Fe0.5B0.5)O3 ceramics. [Copyright &y& Elsevier]

0.94Bi 0.5 (Na 0.78 K 0.22) 0.5 Ti 1- x Ta x O 3 -0.06Ba 0.95 Sr 0.05 TiO 3 (BNKT-BST-100 x Ta, for x = 0,0.005, 0.010, 0.015, 0.020 and 0.025) lead-free ceramics were fabricated by the solid-state reaction technique. Microstructure, dielectric, ferroelectric and fatigue performances of BNKT-BST-100 x Ta ceramics had been systemically studied. The XRD patterns confirmed that Ta5+ ions had completely dissolved into the lattice of BNKT-BST-100 x Ta ceramics. Meanwhile, the temperature of R 3 c -PNRs (T s) was found to shift towards room temperature in dielectric permittivity curves with the introduction of Ta5+ ions. In addition, the highest unipolar strain of 0.32% with the corresponding normalized strain of 458 pm/V was obtained for x = 0.020 under the applied electric field of 70 kV/cm. The large electro-strain was cause by intrinsic effect of the crystal and the external electric field. Moreover, the excellent strain fatigue resistance indicated the prepared ceramics are promising candidates for actuators and stress sensors. [ABSTRACT FROM AUTHOR]

Compositionally graded thick films based on lanthanum-substituted barium titanate solid solutions Ba 1−x La x Ti 1−x/4 O 3 (BLT, x=0.02, 0.04, 0.06) are prepared by tape casting and their phase structures, surface morphologies, dielectric and tunability properties have been examined. Compared with single-layered BLT film, compositionally graded BLT02/04/06 film with three-layered sandwich-structure has better temperature stability in dielectric and tunability properties. Curie peak is broadened, dielectric loss is reduced, and more importantly, it has moderate permittivity and high tunability (>35%) in a temperature range of 25–75 °C, which is beneficial for practical applications of tunable devices. [ABSTRACT FROM AUTHOR]

Ba 1−x Y x TiO 3 (BYT), BaTi 1−y Y y O 3−y/2 (BTY) and Ba 1−z Y z Ti 1−z Y z O 3 (BYTY) are prepared by using a solid state reaction method. Their lattice parameters and solubility are determined. And the correlations between doping sites, concentrations and electrical properties are studied. Doping Y 3+ at A-site, which is associated with the electron compensation, leads to high conductivity in BYT, accompanied by giant permittivity and large dielectric loss. However, BTY is relative insulating since its doping mechanism is dominated by the charge compensation of oxide ion. Although BYTY is self-compensated, it behaves more semiconductive, which is probably due to the oxygen loss during the sintering at high temperature. [ABSTRACT FROM AUTHOR]

Ceramic capacitors are extremely expected to attain the high dielectric permittivity (ε′) and low loss tangent (tan δ) stabilized in an ultra-wide operating temperature range. In this work, we improved ε′ , tan δ and their temperature stability by tailoring the distortion of oxygen octahedron with a different chemical composition in the K 0.5 Na 0.5 NbO 3 -based materials, and the relationships among the composition, crystal structure and dielectric performances were systematically investigated. By designing a series of material systems of K 0.5 Na 0.5 NbO 3 -0.02Bi M O 3 {KNN- M , M : Al, Fe, (Ti 0.5 Mg 0.5), (Ti 0.5 Zn 0.5), (Nb 1/3 Zn 2/3)}, the decreased distortion of oxygen octahedron and enhanced symmetry in crystal structure could be well established, and a high dielectric permittivity (ε' = 1130 ± 15%) with stability in 25 °C–500 °C range was achieved in the KNN-NbZn ceramics. Particularly, a low loss tangent (tan δ ≤ 3%) was maintained up to 360 °C in the ceramics. Therefore, a balanced development of ε' , tan δ and their temperature stability was achieved in the KNN-NbZn materials and we consider this work will bring a clear understanding about the temperature-stable behaviors of dielectric properties in KNN-based ceramic capacitors. Image 1 • High dielectric permittivity (ε' = 1130 ± 15%) with stability in 25 °C–500 °C range was achieved in the KNN-NbZn ceramics. • The low loss tangent (tan δ ≤ 3%) was maintained up to 360 °C in the KNN-NbZn ceramics. • A balanced development of dielectric permittivity, loss tangent and their temperature stability was achieved. [ABSTRACT FROM AUTHOR]