Effects of Sr2+ substitution on the structural,dielectric, and piezoelectric properties of PZT-PMN ceramics

This study described the structural, dielectric, and piezoelectric behavior of Pb_1?x Sr _x [(Zr_0.52Ti_0.48)_0.95(Mn_1/3Nb_2/3)_0.05]O₃ ceramics (PSZT-PMN, x = 0, 0.025, 0.050, and 0.075), prepared by a semi-wet route. X-ray diffraction, dielectric, and piezoelectric investigations were carried out to analyze the crystal structure. The relative dielectric constant and dielectric loss were both calculated as the functions of temperature. The room-temperature dielectric constant reaches a maximum for a Sr²⁺-modified PZT-PMN ceramic with an x value of 0.050, which corresponds to the morphotropic phase boundary (MPB). Raman spectroscopy studies also confirm the existence of this MPB for x = 0.050. The piezoelectric strain coefficients (d ₃₃) value shows a maximum response for this composition. In addition, the phase transition temperature decreases significantly when the Sr²⁺ concentration increases in the PZT-PMN ceramics.     

Microstructure, crystalline phase and electrical properties of Li0.06(Na0.5K0.5)0.94Nb(1−2x/5)Mg x O3 lead-free piezoelectric ceramics

MgO-modified Li_0.06(Na_0.5K_0.5)_0.94NbO₃ (L₆NKN) lead-free piezoelectric ceramics were synthesized by normal sintering at a relatively low temperature of 1000°C. The crystalline phase, microstructure, and electrical properties of the ceramics were investigated with a special emphasis on the influence of MgO content. The addition of MgO effectively improves the sinterability of the L₆NKN ceramics. X-ray diffraction analysis indicates that the morphotropic phase boundary (MPB) separating orthorhombic and tetragonal phases for the ceramics lies in the range of Mg doping content (x) from 0.3at% to 0.7at%. High electrical properties of the piezoelectric constant (d ₃₃=238 pC/N), planar electromechanical coupling coefficient (k _p=41.5%), relative dielectric constant (? _r=905), and remanent polarization (P _r=38.3 μC/cm²) are obtained from the specimen with x=0.5at%, which suggests that the Li_0.06(Na_0.5K_0.5)_0.94Nb_(1?2x/5)Mg _x O₃ (x=0.5at%) ceramic is a promising lead-free piezoelectric material.     

Improvement in the piezoelectric temperature stability of （K0.5Na0.5）NbO3 ceramics

Through an analysis of the temperature stability of(K0.5Na0.5)NbO3(KNN)based ceramics and KNN solid solutions,we propose a method to enhance the temperature stability of KNN materials.These materials are valuable for their piezoelectric properties.To verify the feasibility of this method,0.9(K1-xNax)NbO3-0.06LiNbO3-0.04CaTiO3(KNLN-CaTiO3)ceramics were designed,and their structure and properties were studied.The results show that KNLN-CaTiO3(x=0.54)ceramics have a good temperature stability over a wide temperature range(25-320°C).Also,they have good piezoelectric properties(d33=152 pC/N in x=0.54).This result confirms the feasibility of our proposed solution for improving the piezoelectric properties of KNN-based ceramics that have poor temperature stability.     

Effect of KNbO3 content on the crystal structure and electrical properties of (1 − x)PbZr0.54Ti0.46O3-xKNbO3 piezoelectric ceramics

(1 ? x)PbZr_0.54Ti_0.46O₃-xKNbO₃ (0 ≤ x ≤ 25mol%) (abbreviated as PZT-xKN) piezoelectric ceramics were successfully fabricated by a traditional sintering technique at 1225°C for 30 min. The influence of KNbO₃ content on the crystal structure and electrical properties of the PZT-xKN piezoelectric ceramics was studied. Samples with 0 ≤ x ≤ 0.20 show a pure perovskite structure, indicating that all KNbO₃ diffused into the crystal lattice of PZT to form a single solid solution in this compositional range. A second Pb₃Nb₄O₁₃ phase is observed in the PZT-0.25KN sample, showing that the maximum solid solubility of KNbO₃ in PZT matrix ceramic is less than 25mol%. Compared with pure PZT piezoelectric ceramics, samples containing KNbO₃ have smaller crystal grains. PZT-0.15KN exhibits excellent piezoelectric properties with d ₃₃ = 209 pC/N.     

Phase modification and dielectric properties of a cullet-paper ash-kaolin clay-based ceramic

Novel ceramics from waste material made of (x) paper ash-(80-x) cullet-20 kaolin clay (10wt% ≤ x ≤ 30wt%) were successfully synthesized using a conventional solid-state reaction technique. Energy-dispersive X-ray analysis confirmed the presence of Si, Ca, Al, and Fe in the waste material for preparing these ceramics. The influence of the cullet content on the phase structures and the dielectric properties of these ceramics were systematically investigated. The impedance spectra were verified in the range from 1 Hz to 10 MHz at room temperature. The phase of the ceramics was found to primarily consist of wollastonite (CaSiO₃), along with minor phases of γ-dicalcium silicate (Ca₂SiO₄) and quartz (SiO₂). The sample with a cullet content of 55wt% possessed the optimum wollastonite structure and exhibited good dielectric properties. An increase of the cullet content beyond 55wt% resulted in a structural change from wollastonite to dicalcium silicate, a decrease in dielectric constant, and an increase in dielectric loss. All experimental results suggested that these novel ceramics from waste are applicable for electronic devices.>     

La~(3+)掺杂Bi_(0.5)(Na_(1-x-y)K_xLi_y)_(0.5)TiO_3陶瓷的微结构与电学性能

利用传统的电子陶瓷工艺制备了La^3＋掺杂Bi0．5（Na1-x-yKxLiy）0．5TiO3无铅压电陶瓷,研究了La^3＋掺杂对该体系陶瓷的介电压电性能与微观结构的影响．结果表明,少量的La^3＋掺杂可以改善该陶瓷的微结构;当掺杂量为0．1％时,该陶瓷体系的压电性能有较大的改善,室温下该体系配方的压电常数d33可达215pC／N,径向机电耦合系数kp达到37．4％,但同时介电损耗增大,机械品质因子降低．当掺杂量达到1．5％以后,陶瓷的压电性能严重下降．     

Relaxor behavior of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 ceramics

n the present work, the phase transitions and relaxor behavior of (1−x)Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃ (PMN-PT, x = 0.2―0.4) ferroelectric ceramics have been investigated by means of X-ray diffraction, di-electric spectroscopy, the P-E hysteresis loop measurements and Raman scattering techniques. Structural analysis revealed that with the increase of PbTiO₃ content, PMN-PT ceramics experienced a gradual phase transition process from rhombohedral to tetragonal. It is usually believed that such kinds of phase transitions resulted in the linear decrease of relaxation degree. Surprisingly, our analy-sis of the dielectric spectra revealed that the indicator of the degree of diffuseness γ reached the maximum value near morphotropic phase boundary (MPB) (x = 0.32), then decreased with the further increase of PbTiO₃ content. The large dielectric relaxor feature near MPB may be attributed to the for-mation of ordered nanodomains, resulting from complex coexisting nanostructures. Further, the P-E hysteresis loop measurements and Raman analysis of the B-site cation order correlated well with the dielectric measurement results. It was found that the hysteresis loop squareness R_sq received the minimum value while the inverse of the value of full wide of half maximum (FWHM) of A_1g mode reached the maximum value at MPB composition, which showed similar trends to γ.     

(Bi0.94(Na0.94-xLix))0.5Ba0.06TiO3压电陶瓷的电性能与微观结构

采用传统陶瓷工艺制备了(Bi0.94(Na0.94-xLix))0.5Ba0.06TiO3(缩写为BNBT6 - xL)无铅压电陶瓷.研究了Li+取代A位Na+后,(Bi0.5Na0.5)0.94Ba0.06TiO3(缩写为BNBT6)陶瓷的物性变化.x在0.01 ～0.11之间变化,BNBT6陶瓷三方-四方共存的晶体...     

Influence of sintering temperature on the structure and piezoelectric properties of ZnO-modified (Li, Na, K)NbO3 lead-free ceramics

ZnO-modified (Li, Na, K)NbO₃ lead-free ceramics with a nominal composition of Li_0.06(Na_0.535K_0.48)_0.94NbO₃+0.7mol% ZnO (LNKN-Z₇) was synthesized normally at 930?C1000°C. The Zn ions incorporated into the A-site at a higher sintering temperature, which changed LNKN-Z₇ to soft piezoelectric ceramics with the mechanical quality factor decreasing from 228 to 192. A phase transition from tetragonal to orthorhombic symmetry was identified by XRD analysis, and the corresponding calculation of lattice parameters was conducted at 970?C980°C. Because of such transitional behavior and fine microstructure, the optimized values of piezoelectric coefficient, planar electromechanical coupling coefficient, and relative dielectric constant were obtained.     

微波烧结法制备Fe2O3掺杂0.55PNN-0.45PZT压电陶瓷及性能

 微波烧结是一种新型、高效的陶瓷烧结工艺,具有升温速度快、节能省时、改善微观结构以及降低烧结温度等特点.本文采用微波烧结工艺制备了Fe₂O₃掺杂的0.55Pb(Ni_1/3Nb_2/3)O₃-0.45Pb(Zr_0.3Ti_0.7)O₃(简写为0.55PNN-0.45PZT)压电陶瓷,烧结温度为1200℃、保温时间为2h.利用X射线衍射(X-ray Diffraction,XRD)、扫描电子显微镜(Scanning Electron Microscope, SEM)、阻抗分析仪及铁电分析仪等测试表征方法,研究了Fe₂O₃掺杂对陶瓷的结构、介电以及压电性能的影响.结果表明,所有陶瓷样品均为钙钛矿结构,随着Fe₂O₃掺杂量的增加,压电和介电性能呈先增加后减小趋势.当Fe₂O₃掺杂量为0.8%(质量分数)时,陶瓷达到最优电学性能：压电常数(d₃₃)、平面机电耦合系数(k_p)、相对介电常数(ε_r)和介电损耗(tanδ)分别为d₃₃=520pC/N,k_p=0.51,ε_r=4768,tanδ=0.026.     

无铅Bi0．5（Na0．90-xKxLi0．10）0．5TiO3-NaNbO3压电陶瓷的微结构与电学性能

采用传统陶瓷工艺制备了Bi0.5（Na0.90-xKxLi0.10）0.5TiO3-NaNbO3无铅压电陶瓷,利用XRD、SEM等测试技术分析表征了陶瓷的结构、表面形貌、介电、压电与铁电性能．研究结果表明,该体系陶瓷具有单相钙钛矿结构,NaNbO3的引入使Bi0．5（Na0．90-xKxLi0.10）0.5TiO3体系的相界发生了移动;随着钾含量的增加,NaNbO3对体系性能的影响越明显．在室温下,该体系表现出较好的压电与铁电性能：压电常数d33和机电耦合系数kp分别达到174pC／N和29．6％,陶瓷样品表现出明显的铁电体特征,剩余极化强度达到33．4μC／cm^2．     

基于Li2MnO3的富锂类高比容量锂离子电池正极材料的研究进展

综述了近几年来基于Li2MnO3的高比容量二元和三元富锂类锂离子电池正极材料的研究进展.重点讨论了富锂材料zLi2MnO3.(1-z)LiMO2(0相似文献   

Spin-orbit coupling and zero-field splitting of the high-spin ferric enzyme-substrate complex: Protocatechuate 3,4-dioxygenase complexed with 3,4-dihydroxyphenylacetate

We used density functional calculations to investigate the electronic origins of the magnetic properties of the high-spin ferric enzyme-substrate complex protocatechuate 3,4-dioxygenase(3,4-PCD).The calculated g-tensors show that ligand-to-metal charge transfer transitions are from the protocatechuate(PCA) and Tyr408 orbitals to the Fe d orbitals,which lead to x-and y-polarized transitions.These polarized transitions require a spin-orbit coupling(SOC) matrix element in the z-direction,Lz(z=z’),resulting in a g z value of 2.0158,significantly deviating from 2.0023.A large zero-field splitting parameter value of+1.147cm-1 is due to △S =-1 spin-orbit mixing with the quartet states for the sextet ground state,accounting for around 73% of the SOC contribution.The SOC matrix elements indicate that the high-spin d 5 system Fe(Ⅲ),3,4-PCD-PCA is a weak spin-crossover compound with an SOC of 31.56 cm-1.     

The development of Bi Fe O3-based ceramics

The multiferroic properties of Bi Fe O3-based ceramics were improved through optimizing their sintering method and doping with certain rare earth elements in pure Bi Fe O3. Some methods, especially liquid-phase sintering method has largely decreased the densities of oxygen vacancies and Fe2in Bi Fe O3-based ceramics, and thus their resistivity became high enough to measure the saturated polarization and the large piezoelectric d33 coefficient under the high electric field of [150 k V/cm. Besides,multiferroic properties were improved through the rare earth elements’ doping in pure Bi Fe O3. Magnetization commonly increases with the proportional increase of Nd,La, Sm and Dy contents up to ＊30 %, while ferroelectric phase can transform to paraelectric phase at a certain proportion. An improved magnetoelectric coupling was often observed at ferroelectric phase with a relatively large proportion. Besides, an enhanced piezoelectric coefficient is expected in Bi Fe O3-based ceramics with morphotropic phase boundaries as they are already observed in thin epitaxial Bi Fe O3 films.     

Microstructure and properties of Ga-modified 0.7BiFeO3-0.3BaTiO3 solid solution

Binary solid solutions 0.7Bi (GaxFe1-x)O3-0.3BaTiO3 (x = 0, 0.025, 0.05, 0.1) ceramics were prepared by traditional ceramic process. All the ceramic samples showed single perovskite phase except the sam- ple with x = 0.1. The effects of gallium doping on microstructure, ferromagnetic, ferroelectric, dielectric properties and conductivity were investigated. The results indicated that Ga-dopant could improve the sintering ability of the solid solution when the Ga content x was below 0.05. When x was over 0.05, the sintering ability of the solid solution was weakened, and the phase structure of 0.7BiFeO3-0.3BaTiO3 solid solution changed from rhombohedral phase into tetragonal ferroelectric phase. The electrical resistivity increased with the Ga content increasing. Both ferroelectricity and ferromagnetism were observed in all the ceramic samples. With the Ga content increasing, the remanent magnetization Mr increased and the magnetic coercive field Hc decreased. However, the remanent polarization Pr fluctu- ated, increasing firstly and decreasing later.     

掺杂SrTiO_3陶瓷的介电性及正电子湮没

本文应用正电子湮没寿命谱方法研究掺杂SrTiO_3陶瓷的介电性.通过对不同掺La量SrTiO_3的介电常数、损耗因子、正电子在样品中的湮没寿命的测量,发现介电常数、损耗因子随掺La量的变化与正电子寿命参量的变化存在着某种关系;文中用Sr空位及La离子与Sr空位缔合体模型解释了这些变化与关系.     

非均相沉淀法制备PLZT富锆陶瓷及其电击穿性能研究*

PZT95/5型铁电陶瓷的抗电击穿强度对材料的实际应用至关重要,实际应用中PZT95/5型铁电陶瓷较低的抗电击穿强度限制了它的应用;选择了PZT95/5型铁电陶瓷材料为研究对象,以提高材料的抗电击穿强度为目的,从材料的制备工艺、材料的微观结构的优化以及电击穿性能等方面,探索提高PZT95/5型铁电陶瓷抗电击穿强度的途径;采用了传统固相法、非均相沉淀法制备出了不同微观结构和性能的PZT95/5型铁电陶瓷;研究表明,采用非均相沉淀法制备了PZT95/5型铁电陶瓷,其介电、压电、铁电性能和抗电击穿性能都优于传统固相法所制备陶瓷的性能;根据弱点导致电击穿的理论,采用韦布尔分布表征和研究了所制备的PZT95/5型铁电陶瓷的电击穿性能。     

铈掺杂对0.70PZN-0.15PT-0.15BT压电陶瓷结构与电性能的影响

采用两步合成法制备了CeO2掺杂Pb1-xCex/2(Zn1/3Nb2/3)0.70Ti0.3Ba0.15O3(0.70PZN-0.15PT-0.15BT-x,x=0.00,0.02,0.04,0.06)压电陶瓷,研究了铈含量变化对0.70PZN-0.15PT-0.15BT-x压电陶瓷材料相结构及其相关电性能的影响.随CeO2含量增加,居里温度升高,当x=0.04时,其压电系数d33达到225pC/N.     

铌铁酸铅-钛酸铅铁电陶瓷的结构相变

 通过钨锰铁矿预合成法制备了铌铁酸铅-钛酸铅(1-x)Pb(Fe_1/2Nb_1/2)O₃-xPbTiO₃ (PFN-PT)铁电陶瓷。X-ray衍射（XRD）测量和密度测试表明,1150 ℃烧结2.5 h制备的PFN-PT陶瓷呈现纯钙钛矿结构和较高的致密度。随着PbTiO₃（PT）质量含量的增加,PFN-PT的晶体结构从三方相向四方相转变,伴随着晶胞体积的减小和钙钛矿结构四方性因子（c/a）的增大。PFN-PT陶瓷呈现明显的介电频率色散现象,随着PT含量的增加,介电常数最大值温度T_m/T_C升高,介电响应从弥散、宽化的介电峰变得相对尖锐,介电损耗减小,频率色散现象减弱。MnO₂掺杂有效地改善了PFN-PT陶瓷的介电性能。w=0.25% MnO₂掺杂的0.66PFN-0.34PT陶瓷100 kHz的最大介电常数ε_m为13254,室温介电损耗tanδ为0.003 63,饱和极化强度P_s为6.18μC/cm2,矫顽场E_c为1.1 kV/mm,压电应变常量d₃₃为98pC/N。     

Ferroelectric and piezoelectric properties of novel relaxor ferroelectric single crystals PMNT

Relaxor ferroelectric single crystals PMNT with the size of 40 mm×80 mm have been grown by a modified Bridgman method and their ferroelectric and piezoelectric properties have been characterized.The properties varied with the compositions and cut types.On the (001) cut,PMNT76/24 single crystals exhibited a dielectric constant of about 3 400,a dielectric loss of tan＜0.7%,a piezoelectric constant d33 of 980 pC/N,an electromechanical coupling factor kt of 0.55 and Tc of about 110℃.Whereas the properties of PMNT67/33 single crystals on (001) cut were better: ε of about 5 300,tanδ＜0.6%,d33 up to 3 000 pC/N,kt 0.64,k33 0.93 and Tc of about 150℃.The piezoelectric properties on other cuts such as (110) and (111) were much lower than those on the (001) cut.The rhombohedral PMNT crystals grown by this method showed more excellent piezoelectric properties than those grown by high temperature solution method and higher value of kt than the rhombohedral PZNT single crystals.It has also been found that the fluctuation in ferroelectric and piezoelectric properties was related to such factors as composition uniformity and poling degree.