溶胶-凝胶法制备(Bi0.5Na0.5)1-xBaxTiO3陶瓷的性能

测量了使用溶胶-凝胶工艺制备的 (Bi0.5Na0.5)1- xBaxTiO3(x=0,0.02,0.04,0.06)系无铅 压电陶瓷的介电、压电和弹性参数.研究发现,该工艺制备的 (Bi0.5Na0.5)0.94Ba0.06TiO3陶瓷具有 此系列最强的压电性能, 与传统工艺制备的该类压电陶瓷相比, 溶胶-凝胶工艺制备的 (Bi0.5Na0.5)0.94Ba0.06TiO3陶瓷具有压电常数( d33=173× 10- 12C/N)、机电耦合系数( kt=56%, kp= 26%)、泊松比(ν =0.3)提高; 频率常数( Nt=2250Hz· m, Np=2810Hz· m)、退极化温度( Td= 75℃)降低以及介电常数(εTr33=820)、介电损耗( tgδ=3.9%)稍大的特点.     

溶胶-凝胶法制备锰掺杂 (Bi0.5Na0.5)0.94Ba0.06TiO3无铅陶瓷的压电特性

用溶胶-凝胶工艺制备了 (Bi0.5Na0.5)0.94Ba0.06TiO3 + x wt% Mn (x=0- 0.4)系列无铅压电陶 瓷.研究发现适量锰的掺杂可以有效地降低材料的介电常数和介电损耗,同时提高材料的退极化 温度,但过量锰的掺杂使得材料的压电特性变差.当锰的掺杂量为 0.1wt%时,陶瓷具有该系列最 大的压电常数( d33=175× 10- 12C/N)、最大的机电耦合系数 kt=56%, kp=26%)、较小的介电损耗 tgδ =2.7%,较高的退极化温度( Td=82℃).     

Ta掺杂对Na0.5Bi0.5TiO3-0.02NaNbO3压电、介电性能的影响

在制备无铅压电陶瓷的前沿探索中首次研究了Ta掺杂对Na0.5Bi0.5TiO3-0.02NaNbO3系压电陶瓷的压电、介电性能的影响.研究表明,掺杂适量的Ta有利于提高其性能.当Ta掺杂量为0.4mol时,压电常数d33达到最大值114pC/N;相对介电常数εT33/ε0、机电耦合系数kp也达到最大值431和0.184;而介电损耗tgδ随Ta含量的增加变化不大.     

MnO_2掺杂0.92[Bi_(0.5)(Na_(0.7)K_(0.25)Li_(0.05))_(0.5)]TiO_3-0.08Ba(Ti,Zr)O_3基无铅压电陶瓷

采用二次合成法制备了新型0.92[Bi0.5(Na0.7K0.25Li0.05)0.5]TiO3-0.08Ba(Ti,Zr)O3+x(wt%)(质量分数)MnO2体系无铅压电陶瓷,研究了陶瓷的晶相结构、表面形貌、压电介电性能。研究结果表明,制备的陶瓷样品均具有单一钙钛矿结构。MnO2的含量为x=0.003时,得到介电损耗低的压电陶瓷:介质损耗tanδ为0.0361,压电常数d33为155pC/N,机电耦合系数kp为0.26,机械品质因素Qm为202;在1160℃,2h的烧结条件下,能够获得致密的无铅压电陶瓷体。     

旋转Y切测定La3Ga5SiO14晶体的压电性能及分析

通过选择合适的晶体切型利用谐振法只测量(yxl)-30°切La3Ga5SiO14晶片的相关参数就得到了La3Ga5SiOi4晶体较为准确的压电参数.其中La3Ga5SiOi4晶体的d11和d14分别为5.59×10-12C/N和-5.01×10-12C/N.(yx1)-30°切La3Ga5SiO14晶片具有较大的机电耦合系数k26≈13%和较大的机械品质因数Qm≈10000.     

Ba,Sr掺杂对K0.47Na0.47Li0.06NbO3基无铅压电陶瓷结构、介电及压电性能的影响

采用传统的固态反应法制备了(K0.47Na0.47 Li0.06 )1-x(Ba0.5Sr0.5)xNbO3无铅压电陶瓷,研究了Ba,Sr掺杂对K0.47Na0.47Li0.06NbO3陶瓷的晶体结构、电畴结构、介电及压电性能的影响.随着Ba,Sr掺杂量的增加,陶瓷样品逐渐由正交相向四方相转变,同时居里温度(Tc)降低,剩余极化率(Pr)、矫顽场(Ec)、介电常数(εr)增加;压电常数(d33)、机电耦合系数(kp)先增加后减小.x=0.5％时陶瓷的压电常数d33达到221 pC/N,机电耦合系数kp为43.1％.     

聚苯胺改性0-3 型PZT/ 聚氨酯复合材料的极化与电性能

以聚苯胺( PANI) 原位聚合改性聚氨酯( PU) 树脂为基体, 锆钛酸铅( PZT) 陶瓷为功能相, 制备了0-3 型压电复合材料, 研究了复合材料极化和电性能。结果表明: 适量PANI 能够有效地提高0-3 型复合材料的极化和压电性能。随着PANI 含量增加, 复合材料的压电系数d33和机电耦合系数kp 迅速增大。当PANI 体积分数为4 %时, 复合材料的d33 = 34 pC/ N , kp = 0.25 , 均达到最大值。复合材料的介电常数和介电损耗随PANI含量的增加而上升。      

Sm2O3掺杂(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3无铅压电陶瓷的制备与性能

采用固相合成法制备了Sm2O3掺杂的(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3(BCZT)无铅压电陶瓷.借助XRD、SEM等手段对该陶瓷的显微结构与电性能进行了研究.结果表明,Sm2O3的掺杂降低了BCZT无铅压电陶瓷的烧结温度并使居里温度点Tc从85℃提高到95℃.当Sm2O3掺杂量为0.02wt%～0.1wt%时,样品具有典型ABO3型钙钛矿结构.Sm2O3掺杂量为0.02wt%时,所得陶瓷样品具有最优综合电性能,其压电常数d33、机电耦合系数kp、机械品质因子Qm、介电损耗tanδ和介电常数εr分别为590 pC/N、0.52、43、1.3%和3372.     

锰掺杂对(Na0.5Bi0.5)0.92Ba0.08TiO3压电陶瓷性能的影响

研究了 Mn掺杂对 (Na0.5Bi0.5)0.92Ba0.08TiO3系陶瓷介电、压电与铁电性能的影响. X- ray衍 射结构分析表明掺杂适量的 Mn得到单一的钙钛矿结构,无第二相出现.当添加 0.3 wt % MnCO3 时,介电常数达到 1850;矫顽场强 Ec降低至 3.54kV/mm;压电常数 d33达到 160× 10- 12 C/N.该 材料的温度稳定性也得到改善.     

改性PLZT陶瓷偏压压电效应的研究

本文讨论了铌和钡改性的PLZT10/65/35铁电陶瓷的横向场诱应变X2,不同温度及偏压下的介电常数K33,平面机电耦合系数kp和弹性柔顺系数SE11,并计算了等效压电常数d31。铌和钡改性的PLZT铁电陶瓷在15kV/cm的电场下横向应变分别为-51×10-4和-4.5×10-4。实验表明它们的k。和d31值可由直流偏压控制,室温下k。的饱和值分别为0.53和0.52,｜d31｜的最大值分别为230pC/N和225pC/N,且压电常数的温度系数都比PMN-PT系陶瓷小得多。     

Nanostructured ceramics of 0.92PbZn(1/3)Nb(2/3)O(3)-0.08PbTiO(3) processed by SPS of nanocrystalline powders obtained by mechanosynthesis

This work reports the successful use of a combination of non-conventional methods of synthesis (mechanosynthesis) and sintering (spark plasma sintering, SPS) for the preparation of nanostructured 0.92PbZn(1/3)Nb(2/3)O(3)-0.08PbTiO(3) (PZN-PT) ceramics. With this approach we achieve not only the stabilization of the PZN-PT perovskite phase in ceramics when sintering is carried out at temperatures between 823 and 873?K, but also good control of the grain growth, necessary to produce nanostructured materials with grain sizes of 15-20?nm. This reduction of the size results in relaxor-type electric behaviour.     

Anisotropy in domain engineered 0.92Pb(Zn1/3 Nb2/3)O3-0.08PbTiO3 single crystal and analysis of its property fluctuations

The orientation dependence of slowness and electromechanical coupling coefficients of 0.92Pb(Zn/sub 1/3/Nb/sub 2/3/)O/sub 3/-0.08PbTiO/sub 3/ (PZN-8%PT) domain engineered single crystal was analyzed based on the measured complete set of elastic, piezoelectric, and dielectric constants. There exist one quasi-longitudinal, one quasi-shear, and one pure shear wave in each of the [100]-[010], [010]-[001], and [001]-[110] planes. The slowness of the quasi-shear wave exhibits strong anisotropy in all three planes, and the coupling coefficient k/sub 33/ and k/sub 31/ reach their maximum in [001] and [110] directions of cubic axis, respectively. Because the composition of the PMN-8%PT system is very close to the morphotropic phase boundary, the extraordinary large piezoelectric coefficients d/sub 31/ and d/sub 33/, and high coupling coefficient k/sub 33/ are very sensitive to compositional variation. We have performed error analysis and proposed an improved characterization scheme to derive a complete data set with best consistency.     

High-Energy Storage Density and Efficiency of the xBi(Mg2/3Nb1/3)O3-(1 − x)(Ba0.8Sr0.2)TiO3 (0.08 ≤ x ≤ 0.14) Lead-Free Perovskite Structured Ceramics

The compounds xBi(Mg_2/3Nb_1/3)O₃-(1 − x)(Ba_0.8Sr_0.2)TiO₃ (xBMN-(1 − x)BST, 0.08 ≤ x ≤ 0.14) are prepared via the traditional solid-state reaction method and the ceramics are well densified in the sintering temperature range of 1280–1330 °C. X-ray diffraction analysis shows that all the ceramics crystallize into perovskite structure. Proper amounts of BMN additions can effectively reduce grain sizes of the xBMN-(1 − x)BST ceramics, resulting in more uniform microstructures. Accordingly, breakdown strength E_b is improved and a maximum value 250 kV cm⁻¹ is obtained in ceramic with x = 0.10. Meanwhile, recoverable energy storage density W_rec of the 0.1BMN-0.9BST ceramics reaches 2.03 J cm⁻³, and energy storage efficiency (η) is 96.8%. When the operating temperature increases to 150 °C, the W_rec and η values are about 1.02 J cm⁻³ under 150 kV cm⁻¹ and 89.8%, respectively.     

Properties of epitaxial, (001)- and (110)-oriented (PbMg1/3Nb2/3O3)2/3-(PbTiO3)1/3 films on silicon described by polarization rotation

Epitaxial (PbMg_1/3Nb_2/3O₃)_2/3-(PbTiO₃)_1/3 (PMN-PT) films with different out-of-plane orientations were prepared using a CeO₂/yttria stabilized ZrO₂ bilayer buffer and symmetric SrRuO₃ electrodes on silicon substrates by pulsed laser deposition. The orientation of the SrRuO₃ bottom electrode, either (110) or (001), was controlled by the deposition conditions and the subsequent PMN-PT layer followed the orientation of the bottom electrode. The ferroelectric, dielectric and piezoelectric properties of the (SrRuO₃/PMN-PT/SrRuO₃) ferroelectric capacitors exhibit orientation dependence. The properties of the films are explained in terms of a model based on polarization rotation. At low applied fields domain switching dominates the polarization change. The model indicates that polarization rotation is easier in the (110) film, which is ascribed to a smaller effect of the clamping on the shearing of the pseudo-cubic unit cell compared to the (001) case.     

Composition dependence of magnetocaloric effect in Pr0.6Ca0.4Mn(1-x)Cr(x)O3 (x = 0.02-0.08)

We report the effect of varying Cr content on magnetic and magnetocaloric properties of Pr0.6Ca0.4Mn(1-x)Cr(x)O3 samples (x = 0, 0.02, 0.04, 0.06 and 0.08). While the parent compound (x = 0) is a charge ordered and antiferromagnetic insulator, Cr doped compounds are ferromagnetic metals with nearly same Curie temperature (T(c) approximately 140 K). We find unusual field-induced meta-magnetic transition above T(c) in x = 0.02 and 0.04 which is absent in x = 0.06 and 0.08. It is suggested that the paramagnetic phase in these compounds is inhomogeneous with coexistence of nano-size ferromagnetic clusters and short range charge ordered clusters. Field induced growth of ferromagnetic nano-clusters and destruction of short-range charge ordering leads to the observed metamagnetic transition, which results in large magnetic entropy change of -deltaS(M) = 5.043, 6, 5.509 and 4.375 J/kg K under deltaH = 5 T, for x = 0.02, 0.04, 0.06 and 0.08, respectively. In addition, large relative cooling power (RCP) found in these materials (327.384, 286.36, 272.22 and 279.936 J/kg) makes it interesting for practical applications. Our study suggests that creation of ferromagnetic nano-clusters in the paramagnetic phase by Mn-site doping in charge ordered compounds provides an alternative approach to achieve high AS(M) and RCP values.     

Complete set of material properties of [011](c) poled 0.24Pb(In(1/2)Nb(1/2))O(3)-0.46Pb(Mg(1/3)Nb(2/3))O(3)-0.30PbTiO(3) single crystal

A complete set of elastic, piezoelectric, and dielectric constants of [011](c) poled multidomain 0.24Pb(In(1/2)Nb(1/2))O(3)-0.46Pb(Mg(1/3)Nb(2/3))O(3)-0.30PbTiO(3) ternary single crystal has been determined using resonance and ultrasonic methods and the temperature dependence of the dielectric permittivity has been measured at 3 different frequencies. The experimental results revealed that this [011](c) poled ternary single crystal has very large transverse piezoelectric coefficient d(32) = -1693 pC/N, transverse dielectric constant ε(11)/ε(0) ~ 7400 and a high electromechanical coupling factor k(32) ~ 90%. In addition, its coercive field is 2 times of that of the corresponding binary 0.7Pb(Mg(1/3)Nb(2/3))O(3)-0.30PbTiO(3) single system with much better temperature stability. Therefore, the crystal is an excellent candidate for transverse mode electromechanical devices.     

Relaxor behavior, polarization buildup, and switching in nanostructured 0.92 PbZn1/3Nb2/3O3-0.08 PbTiO3 ceramics

The relaxor-type behavior, electrical polarization buildup, and switching in 0.92Pb(Zn(1/3)Nb(2/3))O(3)-0.08PbTiO(3) nanostructured ceramics with a grain size of approximately 20 nm is reported for the first time. This composition presents the highest-known piezoelectric coefficients, yet phase stability is an issue. Ceramics can only be obtained by the combination of mechanosynthesis and spark-plasma sintering. The results raise the possibility of using nanoscale, perovskite-relaxor-based morphotropic-phase-boundary materials for sensing and actuation in nanoelectromechanical systems.     

Phase-transition temperatures and piezoelectric properties of (Bi1/2Na1/2)TiO3-(Bi1/2Li1/2)TiO3-(Bi1/2K1/2)TiO3 lead-free ferroelectric ceramics.

The phase-transition temperatures and piezoelectric properties of x(Bi(1/2)Na(1/2))TiO3-y(Bi(1/2)Li(1/2))TiO3-z(Bi(1/2)K(1/2))TiO3 [x + y + z = 1] (abbreviated as BNLKT100(y)-100(z)) ceramics were investigated. These ceramics were prepared using a conventional ceramic fabrication process. The phase-transition temperatures such as depolarization temperatures T(d), rhombohedraltetragonal phase transition temperature T(R-T), and dielectric-maximum temperature T(m) were determined using electrical measurements such as dielectric and piezoelectric properties. The X-ray powder diffraction patterns of BNLKT100(y)-100(z)) show the morphotropic phase boundary (MPB) between rhombohedral and tetragonal at approximately z = 0.20, and the piezoelectric properties show the maximum at the MPB. The electromechanical coupling factor k(33), piezoelectric constant d(33) and T(d) of BNLKT4-20 and BNLKT8-20 were 0.603, 176 pC/N, and 171 degrees C, and 0.590, 190 pC/N, and 115 degrees C, respectively. In addition, the relationship between d33 and Td of tetragonal side and rhombohedral side for BNLKT4-100z and BNLKT8-100z were presented. Considering both high Td and high d(33), the tetragonal side of BNLKT4-100z is thought to be the superior composition. The d(33) and T(d) of BNLKT4-28 were 135 pC/N and 218 degrees C, respectively. Moreover, this study revealed that the variation of T(d) is related to the variation of lattice distortion such as rhombohedrality 90-alpha and tetragonality c/a.     

A 3.7 MHz phased array probe using 0.91Pb(Zn(1/3)Nb(2/3))O(3)-0.09PbTiO(3 )

A novel 128-channel phased array probe for echocardiography with a center frequency of 3.7 MHz using 0.91Pb(Zn(1/3)Nb(2/3))O(3)-0.09PbTiO(3 ) (PZN-9%PT) single crystal has been fabricated to realize greater sensitivity and broader bandwidth properties. The echo amplitude of the PZN-9%PT single-crystal probe is about 5 dB higher than that of the conventional lead airconate titanate (PZT) ceramic probe, and the fractional bandwidth is about 25 percentage points broader. The quality of B mode images obtained by the PZN-9%PT probe satisfies the performance of the two types of conventional PZT ceramic probes that have center frequencies of 2.5 and 3.75 MHz. At the reference frequency of 3 MHz, the Doppler sensitivity of the PZN-9%PT probe is about 5 dB higher than that of the 3.75 MHz PZT probe; the blood flow of a pulmonary vein in a hard-to-image patient is much more clearly imaged than in the case of using the PZT probe. These superior images are attributable to the use of sufficiently large PZN-9%PT single crystals obtained by the self-flux method.     

(1-x)CaTiO3-xLi1/2Sm1/2TiO3陶瓷的微波介电性能研究

采用固相法制备了(1-x)CaTiO3-x(Li1/2Sm1/2)TiO3系列微波介质陶瓷材料,研究了该体系的相组成、烧结性能和微波介电性能之间的关系.结果表明:在x=0.1～0.9mol范围内,(1-x)CaTiO3-x(Li1/2Sm1/2)TiO3体系均形成了单一的斜方钙钛矿结构;x=0.1～0.5和x=0.6～0.9组分的最佳烧结温度分别为1250和1300°C;介电常数εr、无载品质因数与谐振频率乘积Qf值、谐振频率温度系数Tf均随着x的增大而减小.当x=0.7时, 1300°C下保温5h烧结得到的材料的微波介电性能为: εr=116.5,Qf=3254GHz,Tf=42.43 ×106/°C.