Enhanced dielectric properties of bismuth titanate/silver composites

Bismuth titanate (BiT) based composites containing silver particles are fabricated by a solution chemical process. Incorporation of silver particles does not result in unwanted reaction phase. SEM micrographs reveal fine silver particles distribute at BiT grain boundaries and into larger BiT plate-like grains. With the addition of silver, the dielectric constant increases up to ∼10 times higher than that of pure BiT ceramic, which can be attributed to the effective electric fields developed around the dispersed metal particles and the percolation effect. Additionally, the dielectric losses are significantly reduced by incorporating silver particles, and the values of BiT/Ag composites are lower than 0.5%. The dielectric properties of BiT/Ag composites are nearly frequency independent in the measured frequency range (1 kHz to 1 MHz).     

Morphotropic phase boundary and electrical properties of lead-free bismuth sodium lanthanum titanate—barium titanate ceramics

The important properties of lead-free piezoelectric ceramics have been investigated from Bismuth Sodium Lanthanum Titanate and Barium Titanate system: (1 − y)(Bi_0.5Na_0.5)_{(1 − 1.5x)}La _x TiO₃(BNLT)—yBaTiO₃(BT) where x = 0.017 and y = 0 − 0.2, respectively. The morphotropic phase boundary (MPB) was found to be around y = 0.1 by the x-ray diffraction and dielectric measurement at various amount of BT. The temperature dependence of dielectric constant (ε _r ) at various value of y showed the diffuse phase transition exhibiting the relaxor type ferroelectrics. The degree of diffuseness increased at a high doping content of about y = 0.15 where the second phase transition (T₂) of the ferroelectric to antiferroelectric phase disappeared. Moreover, this sample had the maximum piezoelectric coefficient (d ₃₃) of about 112 pC/N with relatively low dielectric constant. The optimum sintering temperatures and the microstructures of the dense BNLT-BT ceramics were also examined.     

Lead-free piezoelectric ceramics based on perovskite structures

The piezoelectric properties of a solid solution based on three components of bismuth sodium titanate (Bi_1/2Na_1/2)TiO₃ (BNT), bismuth potassium titanate, (Bi_1/2K_1/2)TiO₃ (BKT), and barium titanate, BaTiO₃ (BT), that is x(Bi_1/2Na_1/2)TiO₃−y(Bi_1/2K_1/2)TiO₃−zBaTiO₃, [, abbreviated as BNBKy:z(x)] and potassium niobate, KNbO₃ (KN) based ceramics, that is KN+MnCO₃ x wt.%, [abbreviated as KN−Mn x], were studied as a lead-free piezoelectric material. In the case of BNBK2:1 system, high piezoelectric properties were obtained near the MPB composition, and the highest electromechanical coupling factor, k ₃₃ and piezoelectric constant, d ₃₃, were 0.58 for BNBK2:1(0.89) and 181 pC/N for BNBK2:1(0.88). Nevertheless, the depolarization temperature, T _d , shifts to lower temperature around the MPB compositions, and the T _d ’s of BNBK2:1(0.88–0.90) are only about 100 °C. On the tetragonal side, the T _d shifts to higher temperature with increasing the lattice anisotropy, c/a. As T _d higher than 200 °C was obtained in the range of x < 0.78, with a k ₃₃ and d ₃₃ for BNBK2:1(0.78) being 0.45 and 128 pC/N, respectively. In the case of Mn doped KN ceramics, dense and non deliquescence KN ceramic were successfully obtained via ordinary firing technique in air by optimizing the fabrication process. Mn doping for KN ceramics was effective to obtain full poling state easily under poling conditions of high temperature and high electric field. As a result, we obtained the excellent piezoelectric properties of k ₃₃ = 0.507 for KN−Mn0.2.     

Low-temperature sintering of MnO2-doped PZT–PZN Piezoelectric ceramics

The effect of MnO₂ addition on the microstructural evolution and piezoelectric properties of low temperature sinterable PZT–PZN ceramics was investigated. When a small amount of MnO₂ (≤0.5 wt% ) was added, the Mn ions were homogeneously dissolved in the PZT–PZN ceramics, leading to full densification at a temperature as low as 930 °C. However, the further addition of MnO₂ hindered the densification, causing the specimen to have a high porosity and small grain size. In addition, as the MnO₂ content increased, the crystal structure of the PZT–PZN changed gradually from a tetragonal to a rhombohedral phase, due to the substitution of Mn for the B-sites in the perovskite structure. The addition of MnO₂ up to a maximum of 0.5% improved the mechanical quality factor (Q _m) of the PZT–PZN ceramics markedly, while keeping the k _p and d ₃₃ values reasonably high. The 80% PZT–20% PZN doped with 0.4 wt% MnO₂ exhibited excellent piezoelectric properties; Q _m = 1,000, k _p = 0.62, and d ₃₃ = 330 pC/N.     

Control of the ferroelectric and electrical properties of Nd substituted bismuth titanate ceramics

Nd-doped bismuth titanate Bi_4?x Nd _x Ti₃O₁₂ ceramics were prepared by a solid state reaction method. The effects of Nd doping on ferroelectric and electrical properties were investigated. With Nd substitution for Bi ion, a BNdT single-phase with Bi-layered perovskite was confirmed. The Nd doping decreased the dissipation factor (tanδ) and the dc conductivity, and increased the dielectric constant and the remanent polarization. A small Nd doping on Bi₄Ti₃O₁₂ leads to a higher remanent polarization and improves the ferroelectric properties.     

改性对钛酸钡基陶瓷储能密度的影响

基于钛酸钡(BaTiO_3)基陶瓷在储能方面的重要应用,介绍了电介质储能的物理基础和影响因素。在此基础上,主要讨论了等价离子掺杂改性、异价离子掺杂改性和包覆改性等对钛酸钡基陶瓷介电性能和储能密度的影响。同时指出优化掺杂改性和包覆改性的组合是提升钛酸钡基陶瓷储能密度的重要途径。     

Effects of complex doping on microstructural and electrical properties of PZT ceramics

The influence of complex dopants including donor and acceptor ions on microstructure and electrical properties of PZT (Zr/Ti = 53/47) ceramics was investigated. The prepared PZT ceramics modified with complex soft dopants, La⁺³ and Nb⁺⁵, showed that the piezoelectric properties were enhanced and stable with the compositional variations, which made it possible to establish the higher reliability and reproducibility of the piezoelectric performances. For 1.0 mol% La and 1.2 mol% Nb doped composition, the maximum value, k _P = 0.66, was obtained. Unlike single element doping, the complex doping of both the donor and acceptor ions caused various compensation effects for the piezoelectric properties of the PZT ceramics. The improved piezoelectric properties, i.e., enhanced Q _m with remaining higher k _p , were obtained in the PZT composition complexly doped with La⁺³ and Fe⁺³. For 1.0 mol% La and 2.0 mol% Fe doped PZT composition, relatively high Q _m and k _p values of 580 and 0.53, respectively, were obtained. It was also shown that the PZT composition had the rather lowered dielectric constant, ε _r = 800, and considerably low loss, tanδ = 0.003. By changing the dopants compositions, the properties can also be tailored over wider range.     

Piezoelectric properties of SrBi2M2− xVxO9 (M = Nb and Ta) ceramics

Vanadium-substituted strontium bismuth tantalate, Sr_0.8Bi_2.2Ta_{2− x}V_xO₉ (SBTVx), and strontium bismuth niobate, SrBi₂Nb_{2− x}V_xO₉ (SBNVx), ceramics were synthesized by a low-temperature processing, and their dielectric, ferroelectric and piezoelectric properties were characterized. With the partial substitution of tantalum or niobium by vanadium cations, the single phase of the ABi₂M₂O₉-type structure was preserved and the sintering temperature was significantly decreased. For the SBNV ceramics, the T _c of 437^∘C for x = 0.0, the vanadium content hardly changed. On the other hand, the T _c of the SBTV ceramics increased from 408^∘C for the non-substituted SBTV to 414^∘C for x = 0.05 and then with the increasing vanadium content, the T _c decreased to 379^∘C for x = 0.20. The remanent polarizations, P _r, of SBTV and SBNV at room temperature were 4.9 and 5.4 μC/cm², respectively. All the obtained independent electromechanical coupling factors of the SBTV0.05 ceramics were as follows: k _p = 0.119, k ₃₁ = 0.073, k ₃₃ = 0.165, k ₁₅ = 0.051 and k _t = 0.134, and the SBNV0.05 ceramics were as follows: k _p = 0.074, k ₃₁ = 0.045, k ₃₃ = 0.175, k ₁₅ = 0.106 and k _t = 0.140. These coupling factors were higher than those of the non-substituted materials. From these results, the vanadium-substituted SBT and SBN-based materials can be expected to be lead-free piezoelectric resonator materials that can be prepared at low sintering temperatures.     

Study of the structure and electrical properties of PMN-PNN-PT ceramics near the morphotropic phase boundary

A series of Pb(Mg_1/3Nb_2/3)O₃-Pb(Ni_1/3Nb_2/3)-O₃-PbTiO₃ (PMN-PNN-PT) ceramics with compositions of (1–x)(0.67PMN-0.33PT)-x(0.64PNN-0.36PT) (x = 0.1–0.9) were synthesized using the columbite precursor method. The phase structures, as well as the dielectric and piezoelectric properties of the ceramics were investigated in detail. X-ray diffraction results demonstrate that all the samples possess a pure perovskite structure. It is found that the morphotropic phase boundary (MPB) region of the PMN-PNN-PT ternary system is located near the line connecting the MPBs of the PMN-PT and PNN-PT binary systems. A high value of the maximum dielectric constant (ɛ_m = 45540, at 1 kHz), together with a high value of the piezoelectric coefficient (d₃₃ = 780 pC/N), were obtained for the composition x = 0.2. The results show that a partial substitution of PNN-PT for PMN-PT can lead to improved electrical properties in this ternary system.     

Influence of vanadium substitution on the conductivity of Bi3.25La0.75Ti3O12 and Bi3.25La0.75Ti2.97V0.03O12 ceramics

We have fabricated Bi_3.25La_0.75Ti₃O₁₂ and Bi_3.25La_0.75Ti_2.97V_0.03O₁₂ ceramics using the conventional solid-state reaction method. We measured their dc conductivity and analyzed the impedance spectroscopy in order to clarify the influence of vanadium substitution for titanium site on Bi_3.25La_0.75Ti₃O₁₂ ceramic. The vanadium substitution for titanium site in Bi_3.25La_0.75Ti₃O₁₂ can reduce the Bi cation and oxygen vacancies. Furthermore, the elimination of these defects, trapped in the grain boundary and grain-electrode interface, significantly reduces the influence of domain pinning, which would be responsible for the improvement in the ferroelectricity and piezoelectricity.     

Structure and ferroelectric property of Nb-doped SrBi4Ti4O15 ceramics

Nb-doped SrBi₄Ti₄O₁₅ (SBT) was produced by conventional method. Structural and ferroelectric properties of SBT were examined as a function of niobium composition. Analyzing the structure futures of SBT by XRD, XPS and Raman spectrum, Nb⁵⁺ substituted Ti⁴⁺ to form NbO₆ octahedron and did not change the structure of SBT. The XRD patterns indicated the formation of the single phase of SBT for x = 0.01and 0.03 and secondary phase of Sr₃Ti₂O₇ appeared when x > 0.1. To compare the effect of Nb doping, the ferroelectric properties (hysteresis loop, piezoelectric coefficient) of Nb-doped SBT were measured. The SBT doped with x = 0.15 was found to exhibit higher remanent polarization with d ₃₃ = 17 pC/N.     

High throughput experimentation for the development of new piezoelectric ceramics

Piezoelectric ceramics based on the perovskite Pb(Zr,Ti)O₃ (PZT) system are widely used as sensors and actuators. The toxicity of lead has motivated research in the field of alternative environmentally friendly lead-free materials. Lead-free piezoelectric ceramics are numerous and in comparison to PZT poorly investigated. The performance of PZT cannot yet be achieved by any lead-free material. Thus High Throughput Experimentation (HTE) shall be applied to discover new lead-free piezoelectric ceramics. In the present study a parallel solid state synthesis method was established for bulk ceramics. Libraries consisting of chemically diverse oxides are produced via the mixed-oxide route. Subsequently, classical piezoelectric parameters such as ɛ, d₃₃ and Curie temperature are screened. The high throughput route, which allows the synthesis and characterisation of over one hundred samples per week, has to be validated with PZT samples. The morphotropic phase boundary was clearly identified and dielectric measurement shows excellent results. The method may be extended to lead-free materials.     

Dielectric and piezoelectric properties of La2O3 doped (Bi0.5Na0.5)0.92(Ba0.8Sr0.2)0.08 TiO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics (Bi_0.5Na_0.5)_0.92(Ba_0.8Sr_0.2)_0.08 TiO₃+x mol% La₂O₃(x = 0, 0.1, 0.3, 0.5, 0.8) were synthesized by conventional solid state reaction. The crystal structure of all compositions is mono-perovskite ascertained by XRD. The grain size decreased and diffuse phase transition behavior was more evident with the increasing amount of La₂O₃. The piezoelectric constant d₃₃ and the electromechanical coupling factor k_p showed the maximum value of 165 pC/N and 0.322 at 0.3% and 0.1% La₂O₃ addition, respectively, and rapidly decreased when La₂O₃ addition over 0.5%. The loss tangent tanδ linearly increased and the mechanical quality factor Q_m linearly decreased with the increasing amount of La₂O₃.     

Investigation on structural and electrical properties of BZT ceramics synthesized at low temperature

Abstract

Due to environmental concerns, lead free ceramics such as KNN- NBT and BT have growing interest in applications such as actuators and sensors. Among them Barium Zirconate Titanate (BZT) has become most attractive because it is derived from two perovskite lattice i.e. Barium Titanate (BaTiO₃) and Barium Zirconate (BaZrO₃). It has been reported that Zirconium substitution in titanium lattice enhances the material properties. In the present paper BZT was prepared using solid state route. By adding a mixture of Li₂CO₃ as a sintering aid, the sample could be sintered at 1150?°C having around 94% of the theoretical density. Prepared samples were then subjected to XRD analysis. X-ray diffraction revealed the formation of single phase material. It is observed that the electrical properties of such low-temperature sintered samples are comparable with BZT samples prepared via conventional sintering at a high temperature. It is also observed that the curie temperature shift towards room temperature for a samples sintered at low temperature.     

Temperature dependence of the dielectric dispersion and ferroelectric properties of neodymium doped bismuth titanate ceramics

Nd-doped bismuth titanate Bi_{4 − x} Nd _x Ti₃O₁₂ ceramics (x = 0–1.0) were prepared by the solid state reaction method. The temperature dependence of the dielectric dispersion and ferroelectric properties were investigated. With the increase of the Nd substitution for Bi ion, the Curie temperature decreased and the corresponding dielectric constant peak broadened. In addition, the strong low-frequency dielectric dispersions were exhibited. The Nd doping decreases the temperature dependence of the ac conductivity and increases the temperature dependence of the remanent polarization, which is caused by the induced polarization by defects, such as bismuth and oxygen vacancies.     

分散剂对钛酸钡介电性能的影响

通过水煮损耗测试、温度特性、电导率和化学分析、瓷片表面显微结构等测试手段,研究了在固相反应制备钛酸钡的工艺中,向BaCO3粉体和TiO2粉体的混合球磨的浆料中加入聚乙烯醇作为分散剂对合成的钛酸钡粉体均匀性的影响。研究结果表明,碱性聚乙烯醇改善合成BaTiO3粉体均匀性的效果最好,介电常数峰值提高了2313、游离BaO含量降低了93.33％。     

Effect of composition and pressure on dielectric property in the Sn-modified lead zirconate titanate ceramics

A detailed study of composition and hydrostatic pressure on the Pb_0.97La_0.02[(Zr_1?x Sn _x )Ti_0.114]O₃ (x?=?0.13,0.19,0.21,0.25) ceramics has provided a detailed view of the dielectric response and phase transition of the technologically important material. The incommensurateness of Sn⁴⁺ has a great influence of the BOCT (BO₆ octahedral in perovskite ABO₃) in the complex perovskite structure. The more Sn doped, the more obvious the character of antiferroelectric behaves and the lower the transformation pressure becomes. The electric energy can be released under the pressure from polarized ferroelectric state to antiferroelectric state. With increasing Sn concentration, the phase transition pressure decreases from 300 to 100 MPa. Dielectric properties were measured as a function of hydrostatic for poled samples. Because of the substitution at the A site, there existed the behavior of dielectric frequency dispersion. Dielectric measurement has the same phase transition point as the test result in the hydrostatic depoling.     

Effect of the firing temperatures on the phase formation,microstructure and electrical properties of BaTi0.91 Sn0.09O3 ceramics synthesized via the solid state combustion method

Abstract

BaTi_0.91Sn_0.09O₃ (BTS) ceramics were synthesized by the solid state combustion method with glycine as the reducting agent and metal nitrates as the oxidants. The calcination and sintering temperatures were in the range of 1200?°C–1300?°C and 1300?°C–1450?°C, respectively, for 2?h. Pure perovskite powders were obtained from the samples calcined at ≥1275?°C for 2?h. The crystal size calculated by Scherrer equation was in the range of 22–30?nm. XRD results of the sintered ceramics showed the coexistence of the tetragonal (T) and orthorhombic (O) phases in all samples, and were confirmed by Rietveld refinement. The grain sizes increased from 9.04 to 29.83 µm when the sintering temperatures increased from 1300?°C–1450?°C for 2?h. The highest density (5.95?g?cm^?3), large piezoelectric strain (d₃₃* = 830?pm/V) and best dielectric constant (ε_r = 14841) were obtained from the sample sintered at 1350?°C for 2?h. This study clearly demonstrates the potential of the solid state combustion method for producing high density and good dielectric properties in BTS ceramics.     

水热法制备四方相钛酸钡纳米粉末的工艺研究

研究了水热法制备四方相钛酸钡纳米粉末的机理,分析了改变实验条件(反应时间、反应温度、溶液PH值、前驱物及前驱物的化学比等)对反应产物的影响,提出由于水热法的密闭性造成反应过程中氧分压只能通过扩散来得到补偿从而影响生成物中钡空位的浓度进而阻碍生成物向四方相转化的进程。通过对改变反应时间所得产物的X-RD和IR分析验证了理论分析的结果     

Effects of ZnO on the piezoelectric properties of Pb(Mn1/3Sb2/3)O3-Pb(Zr,Ti)O3 ceramics

Perovskite-type 0.05 Pb(Mn_1/3Sb_2/3)O₃-0.95 Pb(Zr_0.5Ti_0.5)O₃ (PMS-PZT) was synthesized by conventional bulk ceramic processing technique. ZnO as a dopant up to 0.5 mol% was incorporated into the PMS-PZT system, and the effects on piezoelectric properties were investigated. Pyrochlore phase was not detected to form during the synthesis of the PMS-PZT system with 0∼0.5 mol% ZnO addition. The highest density of 7.92 g/cm³ was obtained when sintered at 1200°C for 2 hrs. Piezoelectric properties as a function of ZnO content were evaluated using a gain phase analyzer. Piezoelectric charge constant (d₃₁) and piezoelectric voltage output coefficient (g₃₁) increased up to −130 pC/N and −24.9 × 10³Vm/N, respectively, with increasing ZnO content. Mechanical quality factor (Q _m) was shown to reduce considerably with increasing ZnO content. When 0.3 mol% of ZnO was added into the system, electromechanical coupling factor (k _p) and relative dielectric constant () reached to the maximum of 56% and 1,727, respectively.