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In this work, cyclotetravanadate Na2SrV4O12 was synthesized at a relatively low sintering temperature of ∼500°C using a solid‐state reaction method. X‐ray diffraction and a transmission electron microscope characterization featured a tetragonal structure that was built by a 3D frame of isolated tetracyclic (V4O12)4−. Dielectric measurements demonstrated strong dependence on frequency and temperature. A low relative permittivity of εr ∼ 8 ± 0.2 and a dielectric (loss tanδ) ∼ 0.4 ± 0.01 was achieved at a frequency of 10 kHz and room temperature. ac impedance and conductivity analysis revealed a thermally activated migration behavior of charge carriers with a short‐range hopping feature. XPS analysis validated the existence of oxygen vacancy and reduction in vanadium (from V5+ to V4+), which gave rise to charged lattice defects. The migration or hopping of such charged defects was responsible for the observed electrical behaviors. Owing to the simple composition, inexpensive raw materials and low density (2.99 g/cm3) make Na2SrV4O12 ceramic a potential candidate for lightweight devices and in photocatalytic degradation and all‐solid‐state ion batteries. [ABSTRACT FROM AUTHOR]

Quenching from sintering temperature enhances the depolarization temperature (Td) in Na1/2Bi1/2TiO3-based ceramics without significant deterioration of piezoelectric properties (d33). In this work, quenching effects in an ergodic relaxor 0.97(0.94Na0.5Bi0.5TiO3–0.06BaTiO3)–0.03AgNbO3 (NBT–6BT–3AN) were investigated based on structure, ferroelectric, and dielectric properties. The ergodicity to nonergodicity transition was obtained by quenching NBT–6BT–3AN above 1000 °C. The temperature stability of the quenching-induced nonergodicity was examined by annealing the quenched sample at 300 °C and 600 °C. The effect of oxygen vacancy on ergodicity to nonergodicity transition was investigated by comparing ferroelectric and electrostrain responses of the quenched and nitrogen-atmosphere-annealed samples. The influence of quenching on the structure including the average crystal structure, phase fraction and lattice distortion and the local structure including bond lengths and ordering of ions was analyzed. The ergodicity to nonergodicity transition upon quenching is ascribed to the contribution of the off-centered Bi3+ ions and ordered local structure. [ABSTRACT FROM AUTHOR]

A new rock-salt type compound, namely Li3MgNbO5, was synthesized using traditional two-step sintering process for the first time. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermal dilatometer and network analyzer. The Li3MgNbO5 ceramic sintered at 1260 °C adopted a cubic structure with Fm-3 m space group and exhibited excellent microwave dielectric properties (MDPs) of εr = 16.2, Q × f = 96796 GHz, and TCF = − 24.8 ppm/°C. The fitting results of the infrared spectrum indicated that the dielectric polarization of Li3MgNbO5 in microwave frequency band was contributed by phonon absorption in infrared band. Furthermore, the negative TCF value of Li3MgNbO5 ceramic was compensated with a traditional TCF compensator ~ CaTiO3. A near-zero TCF value of + 1.2 ppm/°C was achieved in the composite 0.96Li3MgNbO5–0.04CaTiO3 ceramics with εr = 18.4 and high Q × f = 86625 GHz, exhibiting a great potential to be applied in microelectronics systems. [ABSTRACT FROM AUTHOR]

0.4(BaCa)LaTiO-0.6Bi(MgTi)O ( x = 0.00, 0.15, 0.30) ceramics were prepared by a conventional mixed oxide route. Crystal structure of the ceramics was determined using XRD. Dielectric constant of the samples decreases with the increase of La content, however, the temperature stability of dielectric constant was improved. For x = 0.3, a near-plateau dielectric constant 700 ± 80, extended across the temperature range, 30-550 °C (at 1 kHz) was obtained. The corresponding loss tangent, tan δ, was ≤0.025 in the temperature range from 93 to 353 °C. All samples show a relaxor behavior and measurement frequency and the temperature ( T ) corresponding to the maximum of dielectric constant follow the Vogel-Fulcher relationship. Compared the dielectric properties of the samples with other materials, the former has highly attractive for developing capacitors over a wide working temperature range. [ABSTRACT FROM AUTHOR]

Crystal structure, piezoelectric, and dielectric properties were investigated in the new lead-free BKT-based piezoelectric ceramics of (1− x)( Bi1/2 K1/2) TiO3- x Bi( Mg2/3 Nb1/3) O3. The morphotropic phase boundary (MPB) of the system between tetragonal and rhombohedral phases lies near the composition of x = 0.02. The optimal piezoelectric property of small-signal d33 is much enhanced to be 96 pC/N ( x = 0.01), which is higher than any other BKT-based compositions. By the introduction of Bi( Mg2/3 Nb1/3) O3, the ceramics exhibit a lower coercive field EC. In addition, a relaxor-like behavior with a frequency-dependent Curie temperature Tm is observed, and high Curie temperature Tm around 380°C is obtained in the investigated system. This study suggests that the piezoelectric properties of BKT can be significantly improved by the means of Bi( Mg2/3 Nb1/3) O3 substitution. [ABSTRACT FROM AUTHOR]

LiF was selected as a sintering additive to improve the sinterability of the 0.996(0.95K0.5Na0.5NbO3-0.05LiSbO3)-0.004BiFeO3lead-free piezoelectric ceramics. Results suggested that at room temperature the phase structure of the studied ceramics shifted from the coexistence of two phases to a phase in which orthorhombic was dominant when the LiF value was higher than 1.5 mol%, meanwhile, a pronounced shift of the Curie point to higher temperature was observed. The sample with 2 mol% LiF exhibited a higher mechanical quality factor Qmvalue of ∼75.18. With increasing temperature from 30 to 120°C, the remnant polarization of the sample increased monotonically. [ABSTRACT FROM PUBLISHER]

(1− x)( K0.5 Na0.5) NbO3- x Ba2 NaNb5 O15 [(1− x) KNN- x BNN, 0 ≤ x ≤0.1] ceramics were prepared by solid-state reaction method. X-ray diffraction analysis of the ceramics revealed that the crystal structure changed from orthorhombic to rhombohedral with increasing BNN content. Dielectric measurement showed that the ceramics exhibited good dielectric temperature stability over a wide temperature range. Basic mechanisms of the conduction and relaxation processes have been investigated using impedance spectroscopy analyses. It was concluded that the conduction and relaxation processes were thermally activated and oxygen vacancies were the possible ionic charge carriers at higher temperatures. [ABSTRACT FROM AUTHOR]

Two novel BaAFeTaO (A = K, Li) ceramics were fabricated through a conventional solid-state sintering process. Both samples were paraelectric phase with tetragonal tungsten bronze structure at room temperature. Dielectric response of the samples was studied by using AC impedance spectroscopy and universal dielectric relaxation law in detail. Dielectric relaxation at high temperatures is attributed to the oxygen vacancies induced by the evaporation of alkali oxide. The relaxation activation energy of the ceramics is lower than half of the band gap E obtained by UV-Vis spectroscopy, which resulted from the emergence of oxygen vacancies at high temperatures. In the visible light region, the samples showed strong absorption with a band gap of about 2.7 eV, which could be applied as a visible light irradiation photocatalyst. [ABSTRACT FROM AUTHOR]

Abstract: CaCu3Ti4O12 (CCTO) powder has been prepared by a molten salt method using the NaCl–KCl mixture. Crystal structure and microstructure of the powder and the resulting ceramics have been characterized by using X-ray diffraction (XRD) and scanning electron microcopy (SEM). Impedance analyzer and current–voltage meter were employed to analyze dielectric and nonlinear (I–V) properties of the CCTO ceramics with different sintering durations and subsequent cooling rates. The values of dielectric permittivity and nonlinear coefficient of the quenched sample were found to be higher than those of the slowly cooled sample. More specifically, the cooling methods (quenching and furnace-cooling) have allowed to adjust; (і) the breakdown voltage within a rather low range of 0.3–4.4kVcm−1; (іі) the nonlinear coefficient between 2 and 6 and (ііі) the giant dielectric permittivity for the ceramics within a range from 5000 to 20000. A double Schottky barrier can be evidenced from the linear behavior between the ln J and E 1/2 in grain boundary regions. The relationship between the electrical current density and the applied electrical field indicates that the potential barrier height Φ B is holding time dependent. [Copyright &y& Elsevier]

Abstract: Structure, defects, non-ohmic behavior and dielectric properties of CaCu3Ti4O12 (CCTO) ceramics with furnace-cooled and water-quenched methods have been systemically investigated. Cooling methods make an influence on reoxidation process and cause changes of electric properties in grains and at grain boundaries. SEM–EDS provides detailed imaging information about Cu-rich phase on the fracture of CCTO ceramics which is explained by the reoxidation reaction during cooling. Morphologies of the water-quenched sample show very small grains floating in bigger grains; whereas they reveal that many grains are surrounded by an exfoliated sheet of Cu-rich phases in the furnace-cooled sample. The polaron relaxation associated with Ti3+ ions and oxygen vacancies occurs at low temperatures, and more Ti3+ ions are remained in the water-quenched sample. The Schottky barrier height (I–V, non-ohmic behavior) associated with the reoxidation of grain boundaries can be modified by cooling method. [Copyright &y& Elsevier]

Abstract: The crystal structure and dielectric properties of 0.95K0.5Na0.5NbO3–0.05BaZrO3 (KNN–BZ) ceramic have been investigated by X-ray diffraction and dielectric measurement. A rhombohedral distortion was caused and the dielectric permittivity near Curie temperature was significantly enhanced by introducing BZ into KNN. The dielectric and conductivity properties of the sample were studied by using AC impedance spectroscopy and universal dielectric relaxation law in detail. The typical high-temperature dielectric relaxation process was confirmed to be related to the oxygen vacancies inside the ceramic. The effect of lattice distortion on the activation energy for oxygen vacancy migration in KNN–BZ was discussed by comparing with KNN and KNN–BaTiO3. [Copyright &y& Elsevier]

Abstract: We report the temperature-dependent x-ray powder diffraction of the Na0.5K0.5NbO3 (NKN)-based piezoelectric ceramics in the range between 320 and 700K. In the case of NKN we have detected the structural phase transition region from the orthorhombic phase to the tetragonal phase over a broad temperature range from 496 to 458K. The region is enlarged and shifted to lower temperature by introducing trace impurity or second component. It is considered that the coexistence of orthorhombic and tetragonal phases in NKN-based ceramics observed near room temperature are essentially due to the shift and enlargement of the phase coexistence region induced by lattice chemical pressure. [Copyright &y& Elsevier]

In this contribution, the novel double-perovskite La 2 Mg(Mg 1/3 Sb 2/3)O 6 has been successfully prepared by solid-state reaction method, and its structure has been determined for the first time by a combination of X-ray and neutron powder diffraction data analysis. The novel material exhibits a thermal expansion of ∼9.1 ppm/°C and a large optical band gap (4.23 eV). The complex impedance data analysis indicates that La 2 Mg(Mg 1/3 Sb 2/3)O 6 features a Debye-like behaviour, with a bulk conductivity, σ b , varying between 10-7-10-4 S ‧cm-1 within 500–900 °C temperature range, and activation energy (E a) of ∼ 1.36 eV. In addition, the microwave dielectric properties of La 2 Mg(Mg 1/3 Sb 2/3)O 6 sintered at 1625 °C display optimized quality factor (Q× f) of ∼ 28,700 GHz (f = 9.65 GHz), a dielectric constant (ε r) of ∼ 20.2 and temperature coefficient of the resonant frequency (τ f) of ∼ − 89 ppm/°C. This work widen the reduced number of A 3 + B 2 / 3 2 + B 1 / 3 5 + O 3 compounds explored so far. [Display omitted] [ABSTRACT FROM AUTHOR]

Effect of order/disorder transition on microwave dielectric characteristics is reported to develop a deeper understanding of structure-property relationship in spinel ceramics. Dense x Li 4/3 Ti 5/3 O 4 -(1- x)Mg 2 TiO 4 (0.6≤ x ≤0.9) spinel ceramics were synthesized and characterized for structural and dielectric properties. The critical order/disorder structural transition was induced when x < 0.8, resulting in the ceramic crystallized into a primary cubic spinel phase, while when x > 0.8, the ceramic crystallized into a disordered face-centered cubic phase. The cation occupation caused this order-disorder transition, which directly influenced the variation in microwave dielectric properties. At x = 0.75 the maximum degree of order was achieved resulting in a maximum quality factor of 55,000 GHz and a near-zero τ f = 2.9 ppm/oC. Dielectric properties decreased sharply after x = 0.8 when the disorder face-centered cubic phase started to crystallize. All the results indicated that cation ordering/disordering plays a critical role in determining the optimum microwave dielectric properties in spinel ceramics. [ABSTRACT FROM AUTHOR]

Abstract: The piezoelectric ceramics (1− x − y)PbTiO3–xBiScO3–yBi(Zn1/2Zr1/2)O3 exhibit greatly enhanced ferroelectric properties above room temperature, between 100 and 200°C. A strong second harmonic generation (SHG) effect was observed below 200°C. The highest remanent polarization (∼40μC/cm2) and lowest coercive field (∼10kV/cm) were obtained at 200°C. X-ray diffraction (XRD) analysis was used to investigate the morphotropic phase boundary (MPB) structure of (1− x − y)PbTiO3–xBiScO3–yBi(Zn1/2Zr1/2)O3 ceramics. Transmission electron microscopy (TEM) results confirm the existence of MPB, where the rhombohedral and tetragonal phases coexist. The results of thermal expansion analysis show a low thermal expansion and stability of this material. The optimal high temperature piezoelectric ceramic is obtained by the composition of 0.05BZZ–0.34BS–0.61PT. [Copyright &y& Elsevier]

Two garnet-type rare-earth-free ceramics, Ca 3 M 2 SiGa 2 O 12 (M = Sn and Zr), were prepared through a solid-state reaction method. The relationship between crystal structure and microwave dielectric properties was investigated. The larger deviation of ε r from ε theo in Ca 3 Zr 2 SiGa 2 O 12 could be ascribed to the rattling Zr4+. The increase in packing fraction and the decrease in FWHM enhance the Q × f value by substituting Zr4+ with Sn4+. The smaller oxygen bond valence in Ca 3 Zr 2 SiGa 2 O 12 indicates a smaller τ f value. Good microwave dielectric properties are obtained with ε r = 9.14 ± 0.02, Q × f = 106,800 ± 1700 GHz and τ f = -45.8 ± 1.8 ppm/°C for Ca 3 Sn 2 SiGa 2 O 12 and ε r = 11.98 ± 0.03, Q × f = 84,200 ± 1500 GHz, and τ f = -32.8 ± 1.4 ppm/°C for Ca 3 Zr 2 SiGa 2 O 12. Furthermore, near-zero τ f values of +5.7 ± 1.9 ppm/°C and +4.5 ± 1.6 ppm/°C appear in 0.95Ca 3 Sn 2 SiGa 2 O 12 -0.05CaTiO 3 and 0.96Ca 3 Zr 2 SiGa 2 O 12 -0.04CaTiO 3 , respectively. [ABSTRACT FROM AUTHOR]

Olivine−type structure microwave dielectric ceramics LiYbSiO 4 with near-zero τ f were fabricated by solid-state reaction process for the first time. The relationships among structural parameters, sintering behavior, vibrational modes and microwave dielectric properties for the ceramics were studied. The variation in ε r could be correlated with Raman shift. The variation in Q×f values was inversely correlated to FWMH and average cation covalency. The τ f values were explained with the bond valence sum of cations. Single phase LiYbSiO 4 ceramics could be obtained at the range of 1100–1140 °C and showed promising microwave dielectric properties with ε r = 7.36 – 7.42, Q×f = 19081 – 25276 GHz and τ f = +4.52 – +8.03 ppm/°C. [ABSTRACT FROM AUTHOR]

Abstract: The piezoelectric ceramics (1− x − y)PbTiO3 − xPbZrO3 − yBi(Ni1/2Ti1/2)O3 exhibit greatly enhanced piezoelectric properties at morphotropic phase boundaries (MPB). X-Ray diffraction (XRD) analysis was used to investigate the MPB structure of (1− x − y)PbTiO3 − xPbZrO3 − yBi(Ni1/2Ti1/2)O3 ceramics. The dielectric, ferroelectric, and piezoelectric properties were systematically investigated. The morphotropic phase boundaries are at x =0.10, 0.20, 25; y =0.46, 0.39, 0.34, respectively. An optimum high temperature piezoelectric ceramic is obtained at the composition of x =0.20 and y =0.39 (d 33 =510pC/N, d ⁎ 33(bi)=462pm/V, Tc =318°C, Ec =20.0kV/cm and Pr =25.5μC/cm2). [Copyright &y& Elsevier]

Abstract The AgNbO 3 antiferroelectric (AFE) ceramics have attracted increasing attention for their high energy storage performance and environmentally friendly characters. In this work, Ag 1–2 x Ba x NbO 3 ceramics were successfully prepared by the conventional solid-state reaction method. The effect of Ba-modification on phase structure, microstructure, and electric properties was systematically investigated. The introduction of Ba2+ ion led to complex cell parameter evolution and significant refinement of grain size. Room temperature dielectric permittivity increased obviously from ~260 for the pure AgNbO 3 counterpart to ~350 for those after adding a small amount of Ba element. Slim P-E hysteresis loops with improved AFE phase were achieved after Ba modification, due to the decrease of tolerance factor. A high recoverable energy density up to 2.3 J/cm3 with energy efficiency of 46% can be obtained for the composition of Ag 0.96 Ba 0.02 NbO 3 , in correlation with the enhanced AFE stability, reduced P r , increased P m and decreased Δ E. Moreover, the Ag 0.96 Ba 0.02 NbO 3 ceramics also exhibited excellent temperature stability in both energy density and efficiency with small variation of < 5% over 20–120 ℃. The results suggest that the electric properties of AgNbO 3 system can be largely tuned after Ba modification, making it a promising candidate for energy storage applications. [ABSTRACT FROM AUTHOR]

In this paper, we proposed an effective strategy to overcome the trade-off between piezoelectric coefficient and the Curie temperature via co-doping of K+ and Nb5+ ions at A/B sites, achieving a combination of high T C and d 33 in BiFeO 3 -BaTiO 3 -based ceramics. The MPB region was confirmed in a very narrow range of x = 0.0075–0.01 by the Rietveld refinement of XRD patterns and Raman spectroscopy deconvolution. An optimized composition with 1 mol% K/Nb co-dopants possesses a high Curie temperature (T C = 604 °C) along with d 33 = 163 pC/N, k p = 43 %, P r = 57.94 μC/cm2， and P s = 68.18 μC/cm2. An outstanding thermal stability to 540 °C was verified via the temperature dependence of d 33 and in situ Raman spectroscopy. This work not only affords a potential lead-free candidate material for the high-temperature piezoelectric application, but also provides a feasible strategy to design high-temperature dielectrics by exploiting the site engineering. [Display omitted] • Phase evolution (R to T) and MPB region of BF-0.25BT-based ceramics were confirmed by XRD and Raman. • Excellent properties T C = 604 °C, d 33 = 163 pC/N, and k p = 43 % were achieved by K/Nb co-doping. • Outstanding thermal stability to 540 °C was verified by temperature dependence of d 33 and Raman. • An effective strategy based on site engineering was proposed. [ABSTRACT FROM AUTHOR]

The structure, morphology and dielectric properties of the oxygen annealed (O 2 -annealed) and untreated (as-prepared) 0.85(K 0.5 Na 0.5 ) NbO 3 -0·15SrZrO 3 (KNN-15SZ) ceramics were investigated. The temperature dependence of dielectric permittivity shows two diffuse dielectric peaks associated with duplex core-shell structure, leading to relatively stable dielectric permittivity in a wide temperature range. Interestingly, the O 2 -annealed sample with the operating temperature range of −104 °C–157 °C could meet the EIA X8R specification, which is superior to the as-prepared one (−98 °C–130 °C) for the EIA X7R specification. Furthermore, the dielectric contribution from cores and shells of both samples was divided by the Lorentz fitting. The relation between relaxation frequency and temperature of both samples obeyed the Vogel-Fulcher law. This finding could pave a possible way to modify dielectric temperature stability for multilayer ceramic chip capacitors applications. [ABSTRACT FROM AUTHOR]

Magnesium has been doped into the B-site of BaBi 0.25 Pb 0.75 O 3− δ to form a solid solution Ba(Bi 0.25 Pb 0.75) 1− x Mg x O 3− δ (0 ≤ x ≤ 0.10) by solid-state reaction. The X-ray, neutron, and selected area electron diffraction are used to confirm that this solid solution crystallizes in triclinic space group P 1. The unit cell volume of Ba(Bi 0.25 Pb 0.75) 1− x Mg x O 3− δ increases with Mg, which is surprising because the radius of Mg2+ is smaller than any radius of Bi3+, Bi5+, Pb2+, and Pb4+. XPS and iodometric titration data of samples show that the oxygen vacancies increase with Mg in Ba(Bi 0.25 Pb 0.75) 1− x Mg x O 3− δ. The increased oxygen vacancies result in increase of Bi3+:Bi5+ and Pb2+:Pb4+ ratios, which is the utmost possible reason for unit cell volume increase. They are all superconductors with T C z e r o (the highest temperature at which the electrical resistivity becomes "zero") between 11.2 and 9.2 K. • Solis solution Ba(Bi 0.25 Pb 0.75) 1− x Mg x O 3− δ (0 ≤ x ≤ 0.10) synthesized successfully by solid-state reaction. • Their crystal structures have been analyzed through powder X-ray, neutron powder and selected area electron diffraction methods. • The unit cell volume increases by increase in Mg in the Ba(Bi 0.25 Pb 0.75) 1− x Mg x O 3− δ (0 ≤ x ≤ 0.10) solid-state reaction. • The increased oxygen vacancies with increase in Mg are the reason for the increase in unit cell volume. • All the synthesized samples are superconducting with superconductive transition temperature T C z e r o of 9.2 K for Ba(Bi 0.25 Pb 0.75) 0.90 Mg 0.10 O 3− δ. [ABSTRACT FROM AUTHOR]

In this paper, a new type of lead-free ceramic of Sr 4−x Ba x SmFe 0.5 Nb 9.5 O 30 (x = 0, 0.25, 0.5, 0.75 and 1, abbreviated as SBSFN) was prepared by high-temperature solid-phase synthesis. With the increase of x, the packing fraction in the unit cell increases, the vacancy decreases, and the orthogonal phase transforms into the tetragonal phase. The XRD and refinement results show the distortion in the BO 6 octahedron variety as the vacancy decreases. When x increases from 0.5 to 1, and the peak value of the dielectric constant (ε r) increases from 215 to 665 (10 kHz). With the fluctuation of the composition, the relaxation phenomenon is obvious. The impedance data show that there are crystal grains and grain boundaries at high temperature, and all samples undergo a relaxation thermal activation process. The breakdown field strength and remnant polarization of the ceramics increase with increasing x, which indicates that the ferroelectric properties of these ceramics improve. • The decrease of A-site vacancy make phase transform and decreases the BO6 octahedron distortion. • The decrease of A-site vacancy increases the relaxation ferroelectricity. • The decrease of A-site vacancy increases the dielectric constant. [ABSTRACT FROM AUTHOR]

AC 3 B 4 O 12 -type perovskite CaCu 3 Ti 4 O 12 (CCTO), □ 0.34 Pr 0.67 Cu 3 Ti 4 O 12 (PCTO), □ 1 Cu 3 Ta 2 Ti 2 O 12 (CTTO), □ 2 Cu 2 Ta 4 O 12 (CTO) ceramics with different concentration cation vacancies were prepared through traditional solid state reaction method. X-ray diffraction analysis indicated that CCTO and PCTO are perovskite cubic with space group Im -3 (no. 204) while CTTO and CTO are Pm -3 (no. 200). Cell parameter of the samples dramatically increases with the increase of cation vacancies. Dielectric permittivity of them maintains very high value of ∼10 4 from room temperature to 550 K but the dielectric loss is depressed with the increase of cation vacancies in the same space group. The dielectric properties and conductivity behavior were described by the Debye relaxation and the universal dielectric response, respectively. The effect mechanism of cation vacancy and crystal structure on carrier transposition were discussed. [ABSTRACT FROM AUTHOR]

Crystal structure, piezoelectric, and dielectric properties were investigated in the new lead-free BKT-based piezoelectric ceramics of (1− x)( Bi1/2 K1/2) TiO3- x Bi( Mg2/3 Nb1/3) O3. The morphotropic phase boundary (MPB) of the system between tetragonal and rhombohedral phases lies near the composition of x = 0.02. The optimal piezoelectric property of small-signal d33 is much enhanced to be 96 pC/N ( x = 0.01), which is higher than any other BKT-based compositions. By the introduction of Bi( Mg2/3 Nb1/3) O3, the ceramics exhibit a lower coercive field EC. In addition, a relaxor-like behavior with a frequency-dependent Curie temperature Tm is observed, and high Curie temperature Tm around 380°C is obtained in the investigated system. This study suggests that the piezoelectric properties of BKT can be significantly improved by the means of Bi( Mg2/3 Nb1/3) O3 substitution. [ABSTRACT FROM AUTHOR]

Abstract: Perovskite structure (1 − x)BaTiO3–xBiAlO3 (BT–xBA, x = 0.05, 0.08 and 0.1, corresponding to BT–5BA, BT–8BA and BT–10BA, respectively) ceramics were prepared by a solid state reaction route. Crystal structure of BT–xBA ceramics was determined by using XRD. Dielectric properties were studied as a function of temperature at different frequencies, which indicated that the phase transition temperature (T m) decreased with increasing x. With increasing temperature, thermal expansion dl/l increased while thermal expansion coefficient α had weak concentration dependence. The Burns temperature was much higher than the transition temperature T m for the BT–5BA and BT–10BA ceramics. Polarization hysteresis loops (P–E), electrostrictive (S–E) and S versus P 2 (S–P 2) at different temperatures were displayed. P max slightly decreased due to thermally activated leakage current, meanwhile, S max decreased at above T m with the contribution of ferroelectric domain reorientation decreased. The electrostrictive coefficient Q value was clearly larger than that of lead-based electrostrictors at room temperature. Furthermore, it exhibited a slim loop with negligible hysteresis and a subtle linear feature at higher temperature. [Copyright &y& Elsevier]

Abstract: Series new Ba4RETiNb9O30 (RE=La, Pr, Nd, Sm, Eu, Gd) compounds and ceramics were prepared by solid state reaction method respectively. The phase structure, microstructure, dielectric and ferroelectric properties of obtained ceramics were systematically investigated. The XRD results show that all ceramics have been determined as pure tungsten bronze phase. The dielectric characterization indicates that the former four ceramics are relaxors with strong diffuse phase transition and frequency dispersion, while the latter two ceramics show diffuse phase transition. Phase transition temperatures and tetragonality of tungsten bronze structure increase with the decrease of the radii of rare earth. All ceramics have ferroelectricity, among them Ba4GdTiNb9O30 has the highest remnant polarization (2Pr) of 5.12μC/cm2. [Copyright &y& Elsevier]

Abstract: (1−x)BaTiO3–xBi(Zn0.5Zr0.5)O3 [(1−x)BT–xBZZ, 0.01≤x≤0.09] lead-free piezoelectric ceramics were prepared by solid-state reaction method. The effects of Bi(Zn0.5Zr0.5)O3 addition on the crystal structure and electric properties of the BaTiO3 ceramics have been investigated. X-ray diffraction demonstrated that the samples exhibited a tetragonal to pseudocubic phase transition. The lattice parameters were found to increase with increasing the amount of BZZ content. Dielectric measurements revealed that the Curie temperature (T c ) shifted to higher temperature with increasing x. Furthermore, the ceramic with x=0.01 exhibited relatively good electrical properties with d 33=195pC/N, k p =17.7%, P r =14.5lC/cm2, and E c =11.13kV/cm. [Copyright &y& Elsevier]

A low-permittivity and low-loss ceramic, Li 4 GeO 4 , was fabricated via solid state reaction route. XRD showed that a single orthorhombic Li 4 GeO 4 phase with olivine structure was prepared over the sintering temperature range of 660–740 °C. Dense ceramic sintered at 720 °C revealed excellent microwave properties, with ε r ~6.99, Q × f ~47,813 GHz (at 15.5 GHz), and τ f ~ − 159.2 ppm/°C. The microwave dielectric performances were analyzed with the intrinsic characteristics of crystal structure by ionic polarizability and Raman spectra. Additionally, the Li 4 GeO 4 ceramic showed good chemical compatibility with Ag sintered at 720 °C. In the low-temperature cofired ceramic (LTCC) application, aforesaid results manifested that Li 4 GeO 4 ceramic was considered as a potential candidate. • A low-permittivity and low-loss ceramic, Li 4 GeO 4 , was fabricated via solid state reaction route. • Dense ceramic sintered at 720 °C revealed excellent microwave properties, with εr ~ 6.99, Q × f ~ 47,813 GHz (at 15.2 GHz), and τ f ~ –159.2 ppm/°C. • The microwave dielectric performances were analyzed with the intrinsic characteristics by ionic polarizability, packing fraction, and Raman spectra. [ABSTRACT FROM AUTHOR]

• Novel low-permittivity microwave dielectric ceramics in garnet-type Ca 4 ZrGe 3 O 12. • A quite unusual coordination for Ca2+ cations located at the octahedral sites. • The deviation between ε theo and ε r might be related to the rattling Zr4+ in B site. • Ca 4 ZrGe 3 O 12 ceramic sintered at 1340 °C showed ε r = 10.68, Q × f = 76900 GHz. Novel low-permittivity microwave dielectric ceramics Ca 4 ZrGe 3 O 12 with garnet structure were fabricated by a traditional solid-state route. A part of the Ca2+ cations are located at the octahedral sites, a quite unusual coordination for this cation in oxygen compounds. The structural characteristics and vibrational modes for the ceramics were studied based on structure refinement and Raman spectra analysis. Owning to the octahedral site is occupied by equivalent Ca2+ and Zr4+ simultaneously, the deviation between ε theo and ε r could be related to the rattling effect of smaller Zr4+ in the octahedron. Optimum microwave dielectric properties were obtained for Ca 4 ZrGe 3 O 12 ceramic sintered at 1340 °C with ε r = 10.68, Q × f = 76900 GHz, and τ f = −41.3 ppm/°C. [ABSTRACT FROM AUTHOR]