Synthesis and electrical properties of (BaTiO3)1 ?x (K0.5Bi0.5TiO3) x solid solutions

(BaTiO₃)_{1 ? x} (K_0.5Bi_0.5TiO₃) _x solid solutions exhibiting positive temperature coefficient of resistance behavior have been prepared using BaTiO₃ presynthesized through oxalate coprecipitation. The peak in their dielectric permittivity has been shown to shift to higher temperatures (above 120°C) with increasing x. We have examined the effect of K_0.5Bi_0.5TiO₃ content on the microstructure of the (BaTiO₃)_{1 ? x} (K_0.5Bi_0.5TiO₃) _x solid solutions. The results demonstrate that, with increasing x, both the minimum and maximum resistivities of the materials in the temperature range of their positive temperature coefficient of resistance behavior increase. The materials prepared using barium titanate presynthesized by the oxalate route have higher Curie temperatures and temperatures where they exhibit positive temperature coefficient of resistance behavior and lower minimum resistivities than do the materials prepared by solid-state reactions.     

Microstructure and piezoelectric properties of lead-free 0.95(Na0.5K0.5)NbO3–0.05(Bi0.5K0.5)Zr1−x Ti x O3 ceramics

0.95(Na_0.5K_0.5)NbO₃–0.05(Bi_0.5K_0.5)Zr_1?x Ti _x O₃ (abbreviated as KNN–BKZT _x ) ceramics were prepared by the conventional solid state method, and the effect of the Ti content on the surface morphology, crystalline structure, and electrical properties of KNN–BKZT _x ceramics were mainly investigated. With the increase of Ti content, the temperature of the orthorhombic–tetragonal (O–T) phases transitions shifted to lower temperatures, and the O–T phase boundary of KNN–BKZT _x ceramics was identified in the composition with 0 ≤ x ≤ 0.3 at room temperature. It was considered that the piezoelectric properties of the ceramics were enhanced significantly owing to the more possible polarization states resulting from the coexistence of two phases. The ceramic with x = 0.2 exhibited optimum properties: d ₃₃ = 260 pC/N, k _p = 0.38, and T _C = 323 °C.     

Ferroelectric and piezoelectric properties of (1 − x) (Bi0.5Na0.5)TiO3–xBaTiO3 ceramics

Lead-free ceramics based on bismuth sodium titanate (Bi_0.5Na_0.5TiO₃, BNT)–barium titanate (BaTiO₃,BT) have been prepared by solid state reaction process. The (1?x)BNT–(x)BT (x = 0.01,0.03,0.05,0.07) ceramics were sintered at 1,150 °C for 4 h in air, show a pure perovskite structure. X-ray diffraction analysis indicates that a solid solution is formed in (1?x)BNT–(x)BT ceramics with presence of a morphotropic phase boundary (MPB) between rhombohedral and tetragonal at x = 0.07. Raman spectroscopy shows the splitting of (TO₃) mode at x = 0.07 confirming the presence of MPB region. The temperature dependence dielectric study shows a diffuse phase transition with gradual decrease in phase transition temperature (T_m). The dielectric constant and diffusivity increases with increase in BT content and is maximum at the MPB region. With the increase in BT content the maximum breakdown field increases, accordingly the coercive field (E_c) and remnant polarization (P_r) increases. The piezoelectric constant of (1 ? x)BNT–(x)BT ceramics increases with increase in BT content and maximum at x = 0.07, which is the MPB region. The BNT–BT system is expected to be a new and promising candidate for lead-free dielectric and piezoelectric material.     

(1 − x)CaTiO3–x(Li0.5Nd0.5)TiO3 for ultra-small dielectrically loaded antennas

Microwave (MW) dielectric ceramics based on the solid solution (1 ? x)CaTiO₃–x(Li_0.5Nd_0.5)TiO₃ (0.25 ≤ x ≤ 1.0) were prepared by conventional solid-state synthesis using the mixed oxide route. Compositions closest to zero τ_f (+65 ppm/°C) were obtained at x = 0.8 where ε_r = 110 and the microwave quality factor, Qf ₀ ? 2600 GHz for samples sintered at 1300 °C. To reduce the sintering temperature and compensate for any Li₂O loss during fabrication, ≤0.5 wt% 0.5Li₂O–0.5B₂O₃ was added as a sintering aid in the form of raw oxides (LBR) and also as a pre-reacted glass (LBG). 0.5 wt% LBR was the most effective, reducing the temperature to achieve optimum density by ~50 °C with no significant deterioration of microwave properties (ε_r = 115, τ_f = +65 ppm/°C and Qf ₀ ? 2500 GHz). The high permittivity and relatively low sintering temperatures (1250 °C) are ideal for the development of low cost ultra-small dielectric loaded antenna, assuming the system can be tuned closer to zero by fractionally increasing x.     

Effects of Co doping on microstructure and properties of (K0.5Na0.5)NbO3–LiSbO3–BiFe(1−x)Co x O3 lead-free piezoelectric ceramics

0.998 [(0.95(K_0.5Na_0.5)NbO₃–0.05LiSbO₃]–0.002BiFe_(1?x)Co _x O₃ (KNN–LS–BF_(1?x)C _x ) lead-free piezoelectric ceramics were prepared by conventional solid-state reaction method. The influences of Co content on the phase structure, microstructure, density and related electrical properties were investigated. The results reveal that the substitution of Co significantly improves the sinterability and the electrical properties of KNN–LS–BF_(1?x)C _x ceramics, sintered at a lower temperature of 1,030 °C, compared with that of KNN–LS–BF ceramics. With increasing x from 0 to 0.8, all samples show a pure perovskite structure, but the grain size increases continuously,and the porosity level reaches it’s lowest value at x = 0.2. The density ρ, piezoelectric constant d ₃₃, coupling factor k _p and dielectric constant ε _r increase with x up to 0.2, and then decrease with further increase in x value, but the variation of dielectric loss tan δ is opposite. The density and electrical properties achieve optimal value of ρ = 4.287 g/cm³, d ₃₃ = 276 pC/N, k _p  = 48 %, ε _r  = 1,284 and tan δ = 1.95 %, when x = 0.2. And Tc ≈ 340 °C at all the variation range of Co content.     

Piezoelectric and dielectric properties of 0.98(Na0.5K0.5)NbO3–0.02Ba(ZrxTi(1−x))O3 ceramics

Lead-free 0.98(Na_0.5K_0.5)NbO₃–0.02Ba(Zr_xTi_(1?x))O₃ (0.98NKN–0.02BZT) ceramics with Zr contents were fabricated by a conventional mixed-oxide method. The results indicate that the Zr/Ti ratio significantly influences the structural, piezoelectric, dielectric, and ferroelectric properties of 0.98NKN–0.02BZT ceramics. For the 0.98NKN–0.02BZT (x = 0) ceramics sintered at 1090 °C, the bulk density increased as the Zr contents decreased and showed a maximum value at x = 0. The Curie temperature of the 0.98NKN–0.02BZT ceramics slightly decreased as the Zr contents increased. The dielectric constant, piezoelectric constant, and electromechanical coupling factor of samples were maximized at x = 0, which might be due to the increase in density. A high d₃₃ = 194 pC/N, k_p = 38% were obtained for the 0.98NKN–0.02BZT ceramics sintered at 1090 °C for 4 h.     

Microstructure and microwave dielectric properties of xSm(Mg0.5Ti0.5)O3–(1 − x)Ca0.8Sr0.2TiO3 ceramics

xSm(Mg_0.5Ti_0.5)O₃–(1 ? x)Ca_0.8Sr_0.2TiO₃ (x = 0.50–0.95) ceramics are prepared by a conventional solid-state ceramic route. The microstructure and microwave dielectric properties are investigated as a function of the x-value and sintering temperature. The single phase solid solutions were obtained throughout the studied compositional range. The variation of bulk density and dielectric properties are related with the x-value. Increasing sintering temperature can effectively promote the densification and dielectric properties of xSm(Mg_0.5Ti_0.5)O₃–(1 ? x)Ca_0.8Sr_0.2TiO₃ ceramic system. With the content of Sm(Mg_0.5Ti_0.5)O₃ increasing, the temperature coefficient of resonant frequency τ _f value decreased, and a near-zero τ _f could be obtained for the samples with x = 0.80. The optimal microwave dielectric properties with a dielectric constant ε _r of 30.1, Q × f of 115,000 GHz (at 8.0 GHz), and τ _f of 8.9 ppm/°C were obtained for 0.80Sm(Mg_0.5Ti_0.5)O₃–0.20Ca_0.8Sr_0.2TiO₃ sintered at 1,550 °C for 3 h, which showed high density and well-developed grain growth.     

Sr_(0.5)Ba_(0.5)TiO_3/La_(0.5)Sr_(0.5)CoO_3双层薄膜的微观结构

采用脉冲激光沉积法在(001)LaAlO_3衬底上制备了Sr_(0.5)Ba_(0.5)TiO_3/La_(0.5)Sr_(0.5)CoO_3薄膜,利用透射电子显微镜对薄膜的微观结构进行了研究。结果表明,底电极La_(0.5)Sr_(0.5)CoO_3在LaAlO_3衬底上外延生长并形成立方-立方取向关系。不同于块体结构,LSCO薄膜发生了结构转变,形成一种氧缺位有序调制结构。整个薄膜由大量取向畴组成,其中包含一些层错与反相畴界等缺陷。生长温度为500℃时,Sr_(0.5)Ba_(0.5)TiO_3薄膜为柱状多晶结构;当温度升高至820℃时,薄膜为缺陷较少的单晶结构。     

Structures and electrical properties of (Na0.5K0.5)NbO3–Li(Ta0.5Nb0.5)O3 lead-free piezoelectric ceramics

Solid solutions of (Na_0.5K_0.5)NbO₃ (NKN) and Li(Ta_0.5Nb_0.5)O₃ (LTN) were investigated as a potential candidate of lead-free piezoelectric ceramics. It was found that the Curie temperature of solid solutions increases slightly with increasing the LTN content and simultaneously the polymorphic phase transition temperature linearly decrease till below room temperature. An orthorhombic to tetragonal phase transformation at room temperature, or a morphotropic phase boundary, in NKN is induced by ~7 at% LTN addition, where the best dielectric, piezoelectric and electromechanical properties are achieved. The 0.94NKN–0.07LTN ceramics possess a dielectric constant of 765, a loss tangent of 0.04 at 1 kHz, a piezoelectric constant d₃₃ of 253 pC/N and an electromechanical coupling factor k_p of 48%.     

Morphotropic phase boundary and electric properties in (1 − x)Bi0.5Na0.5TiO3–xBaSnO3 lead-free piezoelectric ceramics

Lead-free piezoceramics of (1 ? x)Bi_0.5Na_0.5TiO₃–xBaSnO₃ (BNT–BS, x = 0, 0.02, 0.03, 0.04, 0.06, 0.09 and 0.12) have been synthesized and investigated. A rhombohedral–tetragonal morphotropic phase boundary (MPB) exists near x = 0.03. The MPB composition shows improved electrical properties: the saturated polarization, remnant polarization, coercive field, piezoelectric coefficient, planar electromechanical coupling factor, and unipolar strain are 35.8, 28.5 μC/cm², and 4.5 kV/mm, 93 pC/N, 0.19, and 0.18 %, respectively. It is also found the introduction of BS can significantly enhance dielectric property. The structural and electrical properties are discussed by comparing with other BNT-based piezoceramics.     

Microstructure and electrical properties of (1 − x)K0.5Na0.5NbO3–x(Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 lead-free piezoelectric ceramics

The (1 ? x)K_0.5Na_0.5NbO₃ ? x(Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ (KNN–BCTZ) lead-free ceramics were fabricated by conventional solid-state sintering technique. The microstructure and electrical properties of the ceramics were investigated. The X-ray diffraction analysis revealed that the ceramics formed a single phase perovskite solid solutions with the symmetry of orthorhombic at x < 0.03. The crystal phase of the ceramics changed from orthorhombic phase to pseudocubic phase when x > 0.04. The coexistence of orthorhombic and pseudocubic (tetragonal) phases was observed near room temperature when 0.03 ≤ x ≤ 0.04. The grains grew up obviously when 2 mol% BCTZ was added, but the grain size was found to reduce gradually with further increasing BCTZ content. The T _C and T _O-T decreased with the increasing BCTZ content. The ferroelectric and piezoelectric properties were abruptly degraded as x ≥ 0.05. Optimum properties (d ₃₃ = 136 pC/N, k _p = 27 %, k _t = 26.5 %, Q _m = 25, P _r = 14.67 μC/cm², E _c = 11.23 kV/cm, T _C = 347 °C, $\varepsilon_{33}^{\text{T}} /\varepsilon_{0} = 8 6 1. 5$ ε 33 T / ε 0 = 8 6 1.5 , tan δ = 0.04) were obtained for the ceramica with x = 0.03.     

Diamagnetic and Electrical Properties of Si x Mo2S3−x (x=0.1, 0.2, 0.33, 0.5) and A0.1Mo2S3−x (A=C, B, and Ru)

Mo₂S₃ doped with Si, C, B, and Ru, is identified to bear the same crystalline structure P2₁/m as that of Mo₂S₃ through XRD analysis. Diamagnetic transitions with χ _m ～10^?4 emu/g?Oe at temperature ranging from 2 K to 6 K were observed in the doped samples of Si _x Mo₂S_3?x (x=0.1, 0.2, 0.33, 0.5). And both of the x=0.2 and 0.5 samples were found to have double diamagnetic transitions with higher T _c at the same temperature of 6.01 K, while Si _x Mo₂S_3?x of x=0.33 displayed an extra ferromagnetic-like response at 63 K. The corresponding transition in resistivity of Si _x Mo₂S_3?x with x=0.1 was noticed to show a mild drop with less than 10 % of its original transition values as measured down to 2 K. But a superconducting-like magnetic field dependence on the phase transition of resistivity was also noted. Its diamagnetic signals were greatly reduced when the applied magnetic fields were raised to 10³ Oes. In the doped samples of A_0.1Mo₂S_2.9 (A=C, B, and Ru), the phase transition in resistivity at 4.08 K, 4.62 K, and 4.35 K, respectively, exhibited similar fashion as that in the case of Si_0.1Mo₂S_2.9.     

The electrostrictive effect and dielectric properties of lead-free 0.5Ba(ZrxTi1−x)O3–0.5(Ba0.75Ca0.25)TiO3 ceramics

Lead-free 0.5Ba(Zr_xTi_1?x)O₃–0.5(Ba_0.75Ca_0.25)TiO₃ (x = 0.25, 0.30, 0.35, 0.40) ceramics have been synthesized by a conventional solid state sintering method. The room temperature ferroelectric and electrostrictive properties of these ceramics were studied. Based on the measured properties, these ceramics showed a typical relaxor behavior. The Curie temperature of BZT–BCT ceramics decreases with increasing the Zr content. The largest electrostrictive strain and electrostrictive coefficient are founded in BZT–BCT ceramic with x = 0.25, the value is 0.16 % and 0.079 m⁴ C^?2, respectively. The polarization, electrostrictive strain and electrostrictive coefficient (Q ₁₁) decrease with increase in Zr concentration. For samples with low Curie temperature, which have large room temperature dielectric constant (ε), electrostrictive coefficient increases (Q ₁₁) is smaller. Because doping can disrupt the long range cation order, and electrostrictive (Q ₁₁) coefficient increases with cation order from disordered, through partially-ordered, simple relaxor and then ordered perovskites, ferroelectrics with a disordered structure have a huge permittivity, but a small electrostrictive coefficient (Q ₁₁).     

Effect of Te Substitution on (Tl0.5Pb0.5)Sr2(Ca1?x Te x )Cu2O7 (x=0.0 to 0.5) Superconductor

The (Tl_0.5Pb_0.5)Sr₂(Ca_1?x Te _x )Cu₂O_7??? (Tl-1212) superconductor for x=0.0 to 0.5 has been prepared and studied by a powder X-ray diffraction method, electrical resistance and AC susceptibility measurements. Most of the samples showed Tl-1212 as the major phase and Tl-1201 as the minor phases. Small amounts of Te substitution (x??0.3) maintained the formation of the Tl-1212 phase but larger amounts led to the formation of 1201 and an unknown impurity phase. The resistance versus temperature curve showed metallic behavior for all samples. The resistance versus temperature curves showed onset transition temperature ( $T_{\mathrm{c\ onset}}$ ) between 92 and 97 K. Our results indicated the combined effects of Te substitution, heating temperature and heating time on the formation and optimization of the (Tl_0.5Pb_0.5)Sr₂(Ca_1?x Te _x )Cu₂O₇ superconductor.     

Synthesis and properties of LiZr2(AsO4)3 and LiZr2(AsO4) x (PO4)3 − x

The LiZr₂(AsO₄)₃ arsenate and LiZr₂(AsO₄) _x (PO₄)_{3 ? x} solid solutions have been prepared through precipitation followed by heat treatment, and characterized by X-ray diffraction, X-ray structure analysis, IR spectroscopy, and impedance spectroscopy. We have established conditions for the crystallization of the arsenate and a continuous series of arsenate phosphate solid solutions (0 ≤ x ≤ 3), which have been obtained as two polymorphs: monoclinic and hexagonal. Using the Rietveld method, we have refined the crystal structures of the polymorphs of LiZr₂(AsO₄)₃ (sp. gr. P2₁/n, a = 9.1064(2), b = 9.1906(2), c = 12.7269(3) Å, β = 90.844(2)°, V =1065.03(5) ų, Z = 4; sp. gr. R $\bar 3$ c, a = 9.1600(4), c = 22.9059(13) Å, V = 1664.44(14) Å, Z = 6) and LiZr₂(AsO₄)_1.5(PO₄)_1.5. Their structural frameworks are built up of AsO₄ tetrahedra—or (As,P)O₄ tetrahedra occupied by arsenic and phosphorus atoms at random—and ZrO₆ octahedra, with the lithium atoms in between. The ionic conductivity of the materials has been measured. The cation conductivity of monoclinic LiZr₂(AsO₄) _x (PO₄)_{3 ? x} with 0 ≤ x ≤ 1 has been shown to exceed the conductivity of lithium zirconium phosphate.     

Dielectric and Piezoelectric Properties of (Na0.5Bi0.5)(Ti1–xMnx)O3 (x = 0–0.1) Modified Ceramics

Inorganic Materials - We have studied the crystal structure and dielectric and local piezoelectric properties of (Na0.5Bi0.5)(Ti1–xMnx)O3 (x = 0–0.1) modified sodium bismuth...     

Effect of bond valence on microwave dielectric properties of (1 − x)CaTiO3–x(Li0.5La0.5)TiO3 ceramics

The origins of microwave dielectric properties (1 ? x)CaTiO₃–x(Li_0.5La_0.5)TiO₃ (0.2 ≤ x ≤ 0.8) ceramics, prepared by a conventional solid-state reaction method, were investigated based on the theory of bond valence. The XRD and SEM results showed that complete solid solutions with orthorhombic perovskite structure were formed in the whole investigated compositional range. The dielectric constant (?_r), quality factor (Q × f) and temperature coefficient of resonant frequency (τ_f) were closely related to B-site, A-site and the difference between A-site and B-site bond valences of ABO₃ perovskite compounds, respectively. As x value increased from 0.2 to 0.8, the dielectric constant increased from 198.3 to 276.8, the Q × f value decreased from 4340 to 1880 GHz, and the τ_f value varied from +489.7 to ?178 ppm/°C. For practical applications, excellent microwave dielectric properties of ?_r = 245, Q × f = 2750 GHz and τ_f = +0.75 ppm/°C were obtained for 0.4CaTiO₃–0.6(Li_0.5La_0.5)TiO₃ ceramics.     

(K0.5Na0.5)NbO3–Bi(Mg0.5Ti0.5)O3 solid solution: phase evolution, microstructure and electrical properties

Lead-free piezoelectric ceramics with the composition of (1 ? x)(K_0.5Na_0.5)NbO₃–xBi(Mg_0.5Ti_0.5)O₃ [(1 ? x)KNN–xBMT, 0 ≤ x ≤ 0.04] were synthesized via solid-state reaction method. X-ray diffraction patterns revealed that the orthorhombic—tetragonal phase transition was present for (1 ? x)KNN–xBMT with increasing the content of BMT. The study of dielectric properties illustrated that both peaks of orthorhombic—tetragonal (T _O–T ) and tetragonal—cubic (T _T–C ) phase transitions shifted to lower temperature. Through adding BMT, the electrical properties of KNN ceramics were obviously improved. The optimized piezoelectric and ferroelectric properties with d ₃₃  = 127 pC/N, k _p  = 36.58 %, P _r  = 22.1 μC/cm² were obtained as x = 0.01.