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The dielectric composite ceramics copper calcium titanate/poly vinylidene fluoride (CaCuTiO/PVDF) with Cu powder as a modified agent are successfully prepared by solution mixing processing and hot pressing method. The relative dielectric constants of these composites are significantly enhanced with increase in the volume fraction of copper powder. These composites also possess stable frequency and thermal stability properties in the frequency range of 100-1 MHz. The dielectric permittivity of the 60 vol%PVDF/20 vol%CCTO/20 vol%Cu composite ceramics is higher two times than those with undoped Cu powder and reaches the maximum value of 135 (1 kHz) at Cu powder concentration of 20 vol%. The results indicate that using Cu powder as a modification agent can greatly enhance the dielectric permittivity of the ceramic-polymer composite and achieve high-stability for super capacitor applications. [ABSTRACT FROM AUTHOR]

A novel lead-free excellent transmittance electro-optic ceramics (1- x)(K0.5Na0.5)NbO3- xLaBiO3 (KNN-LB, x = 0.000, 0.005, 0.010, 0.015, 0.020, 0.025, 0.040, 0.060) were fabricated by traditional pressureless ceramics processing procedure. The effects of LaBiO3 dopant concentration x on the microstructure, phase transition, optical property, and electrical properties were studied systematically. The X-ray diffraction results indicated that the KNN- LB ceramics with x ≥ 0.025 have the pseudocubic phase. The morphology, density, and microstructure of the KNN- LB ceramics were characterized by scanning electronic microscopy and optical microscopy. In particular, the KNN- LB ceramics (0.05 mm thickness) with x = 0.025 exhibited the highest transmittance of 74.00% in the visible spectrum comparable to the 72.00% transmittance of the lead lanthanum zirconate titanate ( PLZT 9/65/35 of 0.127 mm thickness). In addition, the related mechanism of transparency variation induced by phase transition and grain size modulation were discussed thoroughly. Finally, the dielectric and ferroelectric properties of as-prepared KNN- LB ceramics were also investigated to further clarify the relationship between transparency and relaxor behavior. [ABSTRACT FROM AUTHOR]

Lead free (BaCa)(TiZr)O (BCZT) ceramics prepared by the sol-gel method (SG) and solid-state method (SS) have been systemically investigated. It is found that Ti concentration, acetic acid concentration, bathing temperature of sol have the influence of different level for ferroelectric and dielectric properties of BCZT ceramics. The optimum parameters for the precursor conditions of BCZT ceramics by the sol-gel method are as follows: the Ti concentration is 0.50 mol/L, the acetic acid concentration is 40 %, the bathing temperature is 50 °C and the aging time is 8 h. The results indicated that BCZT-SG ceramics with the high density and fine-grained microstructure calcined at 1000 °C and sintering at 1420 °C for 6 h exhibit outstanding electrical and energy storage properties, which are as follow: P = 12.15 µC/cm, E = 1.78 kV/cm, d = 558 pC/N, k = 0.56, ε = 16,480, ε = 2234 and W = 0.52 J/cm. Compared with BCZT ceramics with higher density prepared by solid-state method (SS), BCZT-SG ceramics all show more excellent performance than those of BCZT-SS ceramics. [ABSTRACT FROM AUTHOR]

Bi 2/3 Cu 3 Ti 4 O 12 (BCTO) ceramics were successfully prepared by traditional solid-state reaction method (BCTO-SS) and sol–gel method (BCTO-SG). Pure perovskite phase and dense structure were obtained in BCTO ceramics prepared by both methods. BCTO-SG ceramics showed a large dielectric constant of ~1.1×10 4 while BCTO-SS ceramics exhibited a low dielectric constant of ~3200. At 100 kHz, the dielectric constant of BCTO-SS ceramics decreased with applied voltage increasing, while the dielectric constant of BCTO-SG ceramics increased with applied voltage increasing. Further study of the relationship between dielectric constant and voltage suggested BCTO-SG ceramics had larger defect concentration than BCTO-SS ceramics. The investigation of complex impedance indicated that the electrical properties of grain boundaries for all BCTO ceramics were evidently affected by applied voltages and the electrical properties of grains were independent of applied voltages. In addition, the non-Ohmic properties of BCTO ceramics were studied in detail. The non-linear coefficients of BCTO-SS and BCTO-SG ceramics were 1.65 and 1.01, respectively. The breakdown electric fields of BCTO-SS and BCTO-SG ceramics were found to be 1.21 and 0.48 kV/cm, respectively. The potential barrier heights of BCTO-SS and BCTO-SG ceramics were calculated to be 0.549 and 0.485 eV, indicating that the potential barriers at the grain boundaries for BCTO-SS and BCTO-SG ceramics are the Schottky-type barrier. [ABSTRACT FROM AUTHOR]

A low sintering temperature is achieved for (Ba 0.85 Ca 0.15 )(Ti 0.90 Zr 0.10 )O 3 (BCZT) piezoelectric ceramics using Ba(Cu 0.5 W 0.5 )O 3 (BCW) as a sintering aid. The effects of the BCW content on the density, phase structure, electrical and mechanical properties are investigated. The addition of BCW content significantly improves the sinterability of the BCZT ceramics, which results in a reduction of the sintering temperature from 1450 °C to 1220 °C and an improvement in both the piezoelectric and mechanical properties. The BCZT ceramics with x = 0.8 wt.% BCW sintered at 1220 °C exhibits outstanding piezoelectric, dielectric and mechanical properties: d 33 = 541 pC/N, k p = 49%, Q m = 107, ϵ r = 5405, tan δ = 0.014 and T c = 78 °C. The ceramics also exhibit higher hardness (78 MPa) and higher fracture toughness (4.7 MPa m 1/2 ). These results indicate that the BCZT–BCW lead-free ceramics sintered at low temperatures are promising for high temperature piezoelectric applications. [ABSTRACT FROM AUTHOR]

BiCuTiO ceramics were synthesized by the sol-gel method. The optimum parameters for the synthesis of precursor powders were as follows: the Ti concentration was 0.62 mol/L, the aging time of the sol was 16 h and the reaction temperature was 40 °C. When calcined at 800 °C and sintered at 1,000 °C, BiCuTiO ceramics with the highest density and fine-grained microstructure were obtained. The resultant ceramics showed outstanding dielectric properties with a dielectric constant (ε′) of ~1.2 × 10 measured at 1 kHz. The dielectric constant was much higher than that of the ceramics with same composition prepared by the solid-state reaction (~0.30 × 10 at 1 kHz). A unique phenomenon was observed in the temperature dependence of dielectric constant. Dielectric relaxation I occurred at ~200 °C was due to the Maxwell-Wagner relaxation. Whereas an additional dielectric relaxation II was observed at ~300 °C only for the sample prepared by the sol-gel method, which was ascribed to the distribution state transition for oxygen vacancies. [ABSTRACT FROM AUTHOR]

Microstructure and electric behaviors of La2/3 Cu3 Ti4 O12 ( LCTO) ceramics prepared by the sol-gel method ( SG) and solid-state method ( SS) have been systemically investigated. The results indicated that LCTO- SG ceramics sintered at 1105°C for 15 h showed larger grain size, higher density, and especially higher dielectric constant up to about 0.9-1.6 × 104 at 102~105 Hz compared to LCTO- SS ceramics. The higher dielectric constant of the LCTO- SG ceramics might be due to the stronger internal barrier layer capacitor ( IBLC) effect. More notably, compared with LCTO- SS ceramics, two kinds of dielectric anomalies, one conduction activation energy value and same activation energies for the conduction and relaxation process in LCTO- SS ceramics, the LCTO- SG ceramics showed three kinds of dielectric anomalies, two values of conduction activation energy, and decrease in conduction activation energy with increasing temperature. The activation energies for the conduction and relaxation process in LCTO- SG ceramics showed great difference below about 210°C, suggesting that the mechanism of electrical conduction and dielectric relaxation seem to be different in LCTO- SG ceramics. These remarkable differences in electric behaviors of LCTO ceramics prepared by sol-gel and solid-state methods were firstly found and analyzed. [ABSTRACT FROM AUTHOR]

Abstract: The addition of BiFeO3 in the ceramics shifts the PPT below room temperature to improve the temperature stability of KNN-based ceramics. The phase structure, microstructure, dielectric, piezoelectric properties and temperature stability of (1− x)[(K0.458Na0.542)0.96Li0.04](Nb0.85Ta0.15)O3–xBiFeO3 piezoelectric ceramics were investigated. The phase structure of these ceramics changed from tetragonal phase to pseudo cubic phase with BiFeO3 additives. The optimal piezoelectric properties were obtained at x =0.004, which were listed as follows: d 33 =261pC/N, tan δ =0.016, K p =0.58, T c =345°C and ɛ r =1116. Especially, the results demonstrated that the PPT of (K0.458Na0.542)0.96Li0.04](Nb0.85Ta0.15)O3 ceramics has been shifted below room temperature successfully by the addition of BiFeO3. The time stability and ageing rate values of the ceramics with x =0.000 were 15% and 7.8%. These values decrease to 4.97% and 6.09% at x =0.004, respectively, showing that the ceramics have better temperature and time stability for the polymorphic phase transition below room temperature. [Copyright &y& Elsevier]

Abstract: In this paper, low temperature sintering of the Bi2(Zn1/3Nb2/3)2O7 (β-BZN) dielectric ceramics was studied with the use of BiFeO3 as a sintering aid. The effects of BiFeO3 contents and the sintering temperature on the phase structure, density and dielectric properties were investigated. The results showed that the sintering temperature could be decreased and the dielectric properties could be retained by the addition of BiFeO3. The structure of BiFeO3 doped β-BZN was still the monoclinic pyrochlore phase. The sintering temperature of BiFeO3 doped β-BZN ceramics was reduced from 1000°C to 920°C. In the case of 0.15 wt.% BiFeO3 addition, the β-BZN ceramics sintered at 920°C exhibited good dielectric properties, which were listed as follows: εr =79 and tan δ =0.00086 at a frequency of 1MHz. The obtained properties make this composition to be a good candidate for the LTCC application. [Copyright &y& Elsevier]

Abstract: Effects of ZnO addition on electrical properties and low-temperature sintering of BiFeO3-modified Pb(Zr,Ti)O3–Pb(Fe2/3W1/3)O3–Pb(Mn1/3Nb2/3)O3 were investigated. The investigations revealed that the sintering temperature can be decreased to 950°C, and the favorable properties were obtained with 0.10wt% ZnO added ceramics. The electrical properties were as follows: d 33 =313pC/N, K p =0.56, tan δ =0.0053, ε r =1407 and T c =295°C, which showed that this system was a promising material for the multilayer devices application. [Copyright &y& Elsevier]

Lead-free Cu 2+ -modified (Ba 0.85 Ca 0.15 )(Ti 0.9 Zr 0.1 )O 3 (BCZT− x Cu 2+ ) piezoelectric ceramics was synthesized by sol-gel method. The effects of Cu 2+ additions on sintering characteristics, the phase structure, microstructure, electrical properties and complex impedance characteristic were investigated systematically. The XRD patterns exhibited a pure perovskite structure without impurity phase in all samples. SEM micrographs, temperature dependence of dielectric constant and polarization-electric field ( P-E ) hysteresis loops indicated that a small amount of Cu 2+ addition affected the properties obviously. The results revealed that the addition of Cu 2+ significantly improved the sinterability of BCZT ceramics which resulted in a reduction of sintering temperature from 1440 °C to 1230 °C. The TG-DSC was analyzed to verify the reaction process of BCZT−Cu 2+ materials. (Ba 0.85 Ca 0.15 )(Ti 0.9 Zr 0.1 )O 3 ceramics with x=0.020 Cu 2+ exhibited good electrical properties: ε m =12,112, T c =360 K, ε r =2614, tan δ =0.026, K p =0.47 and d 33 =382 pC/N. The results indicated that Cu 2+ -modified BCZT ceramics could be a promising candidate for commercial purposes. [ABSTRACT FROM AUTHOR]

Rare earth element neodymium was adopted to refine grain and in turn increase the volume of grain boundary of Y 2/3 Cu 3 Ti 4 O 12 ceramics, which could strongly increase the resistance of grain boundary. Proper amount of Nd substitution in Y 2/3− x Nd x Cu 3 Ti 4 O 12 ceramics could significantly depress the low-frequency dielectric loss. When the doping level is 0.06 and 0.09, the samples exhibited a relatively low dielectric loss (below 0.050 between 0.3 and 50 kHz) and high dielectric constant above 11000 over a wide frequency range from 40 Hz to 100 kHz. Based on the ɛ′- T plots, dielectric relaxation intensity was substantially weakened by Nd doping so that the temperature stability of dielectric constant was improved obviously. The correlations between low-frequency dielectric loss and the resistance of grain boundary were revealed. After Nd doping, the activation energies for the conduction behavior in grain boundaries were significantly enhanced, and the activation energies for the dielectric relaxation process in grain boundaries were slightly influenced. [ABSTRACT FROM AUTHOR]

Considering the contribution of the mixed valence structure of Ti 3+ and Ti 4+ to the semiconductivity of grain, compositions with the formula of Y 2/3 Cu 3 Ti 4+ x O 12 were designed and prepared. The dielectric bulk responses of Y 2/3 Cu 3 Ti 4+ x O 12 ceramics were explored in detail. Changing Ti stoichiometry gives rise to an increase of the intrinsic permittivity. Y 2/3 Cu 3 Ti 3.925 O 12 ceramic exhibits a higher intrinsic permittivity of ~120 at 60 MHz than that of pure Y 2/3 Cu 3 Ti 4 O 12 ceramics (87 at 60 MHz). Additionally, the activation energies of bulk responses are significantly enhanced by changing Ti stoichiometry, which is closely linked with the increase of Ti 3+ /Ti 4+ . [ABSTRACT FROM AUTHOR]

Abstract: The phase structure, microstructure and dielectric properties of Na0.5Bi0.5−x La x Cu3Ti4O12 (NBLCTO) ceramics were investigated. La3+ substitution had a great influence on the phase structure and dielectric properties. The results showed that the pure phase could be more easily obtained when substituting La3+ for Bi3+. Under the same processing condition (970°C for 7.5h) and measuring condition (10kHz around room temperature), NBLCTO ceramics with x =0.10 possessed the highest permittivity (1.02×104) and lowest dielectric loss (0.022). The obtained NBLCTO ceramics with x =0.10 also had good frequency stability and good temperature stability (−1.87% to +3.27%) from −60°C to 120°C at both 1 and 10kHz. Complex impedance results revealed that the grain resistance R g was 7.18Ωcm and the grain boundary resistance R gb was 1.19×106 Ωcm. [Copyright &y& Elsevier]

Abstract: The Ca1−x Sr x Cu3Ti4O12 (CSCTO) giant dielectric ceramics were prepared by conventional solid-state method. X-ray diffraction patterns revealed that a small amount of Sr2+ (x<0.2) had no obvious effect on the phase structure of the CSCTO ceramics, while with increasing the Sr2+ content, a second phase of SrTiO3 appeared. Electrical properties of CSCTO ceramics greatly depended on the Sr2+ content. The Ca0.9Sr0.1Cu3Ti4O12 ceramics exhibited a higher permittivity (71,153) and lower dielectric loss (0.022) when measured at 1kHz at room temperature. The ceramics also performed good temperature stability in the temperature range from −50°C to 100°C at 1kHz. By impedance spectroscopy analysis, all compounds were found to be electrically heterogeneous, showing semiconducting grains and insulating grain boundaries. The grain resistance was 1.28Ω and the grain boundary resistance was 1.31×105 Ω. All the results indicated that the Ca0.9Sr0.1Cu3Ti4O12 ceramics were very promising materials with higher permittivity for practical applications. [Copyright &y& Elsevier]

Abstract: La2O3-doped Bi0.5(Na0.68K0.22Li0.1)0.5TiO3 lead-free piezoelectric ceramics have been successfully prepared by conventional solid state method and the effects of La2O3 doping on microstructure and electrical properties of the ceramics were investigated. The X-ray diffraction patterns demonstrated all ceramics possessed pure perovskite structure with rhombohedral symmetry. The temperature dependence of dielectric constant and dielectric loss revealed two abnormal dielectric peaks of Td and Tm , which implied that from room temperature to 500 °C all ceramics underwent two phase transitions which were from ferroelectric to anti-ferroelectric and anti-ferroelectric to paraelectric, respectively. It was also found that the transition temperature Td decreased with the addition of La2O3. Diffuse phase transition and frequency dispersion of the dielectric constant were observed in all ceramics. Dielectric relaxor behavior obeyed the modified Curie–Weiss law. The results revealed that all samples had relaxor characteristics. In addition, for the ceramics with 0.1 wt.% La2O3, optimized electrical properties were obtained, which were as follows: ɛr  = 1254 (1 kHz), tan δ = 0.0483, d 33 = 192 pC/N, Kp  = 0.27, Pr  = 29.1 μC/cm2, and Ec  = 29.0 kV/cm. [Copyright &y& Elsevier]

The effects of Na + concentration on the microstructural, dielectric, ferroelectric and transparent properties of (Sr 0.925 Ca 0.075 ) 2.5–0.5 x Na x Nb 5 O 15 (SCNN; 0.4 ≤ x ≤ 1.0) ceramics prepared using a conventional solid-state reaction method were investigated. X-ray diffraction results showed that the phase structure transitioned from tetragonal to orthorhombic tungsten bronze along with the structural type changing from ‘unfilled’ to ‘filled’ state. The NbO 6 octahedron became more distorted and had higher interaction strength when introducing Na + in A-sites to decrease the structural vacancies, leading to the improvement of dielectric and ferroelectric properties. The dielectric spectra of all specimens showed two broad dielectric anomalies: a high-temperature anomaly (the ferroelectric phase transition) and a low-temperature anomaly caused by the subtle structural effects in ‘unfilled’ SCNN ceramics, which evolved into the ferroelastic phase transition in ‘filled’ SCNN ceramics. [ABSTRACT FROM AUTHOR]

Colossal permittivity in tantalum-doped TiO 2 (Ta x Ti 1− x O 2 ) ( x = 1%, 2%, 3%, 4%, 5% and 6%) fabricated by the conventional solid-state reaction method in N 2 atmosphere were achieved. Especially, by optimizing components and sintering temperatures, the dielectric loss could significantly decreased. The effects of Ta doping on their microstructure, dielectric properties, and temperature stability were revealed in detail. When the composition with x = 5% and sintered at 1400 °C, the dielectric constant reached to ∼30000 and the dielectric loss decreased to 3%. Interestingly, all the samples also exhibit good temperature stability of dielectric properties in a wide temperature range from 100 to 350 K. Based on XPS analysis, the formation of defect-dipole clusters, e.g. 2 ( Ta 5 + ) Ti · → 4 ( Ti 3 + ) Ti ′ ← V o ·· should be mainly responsible for the improved dielectric properties in tantalum-doped TiO 2 . [ABSTRACT FROM AUTHOR]

High-temperature ceramic capacitors has become an important research topic with the upgrading and development of emerging industries such as electronic information. In this study, a series of lead-free (1- x)Bi 0.5 Na 0.5 TiO 3 - x CaSnO 3 (BNT- x CS) ceramics with good temperature stability were designed and synthesized using a solid-state reaction method. The temperature stability were improved with the addition of CS, which is closely related to the suppression of the ferroelectricity of BNT ceramics. Remarkably, BNT-0.15CS ceramic displayed a superior temperature stability of Δε/ε 150 °C ≤ ± 15% in the range of − 96 ∼ 500 °C, as well as a low dielectric loss tanδ = 0.003 at 150 °C (1 kHz). The finding in this work not only explores how to improve the temperature stability of BNT and related materials, but also provides candidate materials for high-temperature ceramic capacitors. • The addition of CS suppressed the ferroelectric properties of BNT ceramics. • BNT-0.15CS ceramics displayed superior temperature stability in the range of - 96–500 ℃. • Recoverable energy density of 1.1 J/cm3 was obtained in BNT-0.15CS ceramics. • This work provides candidate materials for high temperature ceramic capacitors. [ABSTRACT FROM AUTHOR]

Polycrystalline (1 − x ) BiFeO 3 – x (Ba 0.85 Ca 0.15 )(Zr 0.10 Ti 0.90 )O 3 [(1 − x ) BFO − x BCZT)] ceramics were fabricated by a solid state reaction method. The phase structure, microstructure, and dielectric, ferroelectric and magnetic properties of the (1 − x ) BFO − x BCZT ceramics were systematically investigated. The crystal structure of the (1 − x ) BFO − x BCZT ceramics transformed from rhombohedral to pseudocubic with increasing x . A morphotropic phase boundary existed at the composition of 0.20 ≤ x ≤ 0.30. The average grain size of the ceramics initially increased to a maximum at x = 0.30 and then decreased. The frequency dependence of dielectric constant and complex impedance plots indicated an electrically heterogeneous microstructure for x ≤ 0.20 caused by the coexistence of Fe 2+ and Fe 3+ . T m and ϵ m decreased with increasing x for 0.25 ≤ x ≤ 0.80, and the hysteresis loops ( P–E ) became slimmer with increasing x . All samples presented weak ferromagnetic ordering, indicating that the substitution of BCZT into the BFO matrix released its potential magnetization. The optimal ferroelectric and magnetic properties, P r of 22.7–27.3 μC/cm 2 and M r of 0.0394–0.0744 emu/g, were obtained at 0.30 ≤ x ≤ 0.35. [ABSTRACT FROM AUTHOR]