铌镁酸铋-钛酸铅压电陶瓷准同型相界附近的性能和相变温度研究

利用传统固相烧结法制备了Bi(Mg_2/3Nb_1/3)O₃-PbTiO₃(BMN-PT)压电陶瓷, 分析了不同PbTiO₃含量对BMN-PT压电陶瓷的晶体结构、介电、压电及铁电性能的影响. XRD结果表明: 合成的BMN-PT陶瓷具有纯钙钛矿结构, 并且在PbTiO₃含量为x=0.60时, 其组分的XRD图谱在衍射角2θ=45°出现明显的分峰, 说明该组分相结构中存在三方和四方相的共存. 压电铁电性能显示, BMN-0.60PT有最大的压电常数d₃₃(~170pC/N)和平面机电耦合系数k_p(0.35), 最小的矫顽场E_c(29.4 kV/cm)及最大的剩余极化P_r(31.4 μC/cm²). 确定了BMN-PT压电陶瓷的准同型相界(MPB)为PbTiO₃含量x=0.60的组分. 介电系数温谱表明介电系数峰值温度(Tm)随着PbTiO₃含量的增大而升高, MPB组分的Tm约为276℃.     

钇掺杂对BSPT高温压电陶瓷铁电性能的影响

利用传统固相法制备了(1-x)Bi(Sc1-yYy)O3-xPbTiO3(BSYPT-x/y)压电陶瓷,采用XRD、SEM、压电工作站等技术表征了体系的晶体结构、微观组织及其铁电性能.发现随着PbTiO3含量的增加,BYSPT-x/y陶瓷相结构由三方结构逐渐转变为四方结构.体系的准同型相界(MPB)位置随BiYO3含量的增加而移向PbTiO3含量更低的一端.在准同型相界附近的BSYPT0.58/0.15陶瓷的电滞回线出现"束腰"现象,这种现象来源于BSYPT0.58/0.15陶瓷内部产生的正极为O2-,负极为Y3+的缺陷偶极子.     

Piezoelectric properties in (K0.5Bi0.5)TiO3-(Na0.5Bi0.5)TiO3-BaTiO3 lead-free ceramics.

Lead-free piezoelectric ceramics with compositions around the morphotropic phase boundary (MPB) x(Na0.5Bi0.5)TiO3-y(K0.5Bi0.5)TiO3-zBaTiO3 [x + y + z = 1; y:z = 2:1] were synthesized using conventional, solid-state processing. Dielectric maximum temperatures of 280 degrees C and 262 degrees C were found for tetragonal 0.79(Na0.5Bi0.5)TiO3-0.14(K0.5Bi0.5)TiO3-0.07BaTiO3 (BNBK79) and MPB composition 0.88(Na0.5Bi0.5)TiO3-0.08(K0.5Bi0.5)TiO3-0.04BaTiO3 (BNBK88), with depolarization temperatures of 224 degrees C and 162 degrees C, respectively. Piezoelectric coefficients d33 were found to be 135 pC/N and 170 pC/N for BNBK79 and BNBK88, and the piezoelectric d31 was determined to be -37 pC/N and -51 pC/N, demonstrating strong anisotropy. Coercive field values were found to be 37 kV/cm and 29 kV/cm for BNBK79 and BNBK88, respectively. The remanent polarization of BNBK88 (approximately 40 microC/cm2) was larger than that of BNBK79 (approximately 29 microC/cm2). The piezoelectric, electromechanical, and high-field strain behaviors also were studied as a function of temperature and discussed.     

Recent developments in high curie temperature perovskite single crystals

The temperature behavior of various relaxor-PT piezoelectric single crystals was investigated. Owing to a strongly-curved morphotropic phase boundary, the usage temperature of these perovskite single crystals is limited by T/sub R-T/- the rhombohedral to tetragonal phase transformation temperature - which occurs at the significantly lower temperatures than the Curie temperature T/sub c/. Attempts to modify the temperature usage range of Pb(Zn/sub 1/3/Nb/sub 2/3/)O/sub 3/-PbTiO/sub 3/ (PZNT) and Pb(Mg/sub 1/3/Nb/sub 2/3/)O/sub 3/-PbTiO/sub 3/ (PMNT) rhombohedral crystals (T/sub c/ /spl sim/ 150-170/spl deg/C, T/sub R-T/ /spl sim/ 60-120/spl deg/C) using minor dopant modifications were limited, with little success. Of significant potential are crystals near the morphotropic phase boundary in the Pb(Yb/sub 1/2/Nb/sub 1/2/)O/sub 3/-PbTiO/sub 3/ (PYNT) system, with a T/sub c/ > 330/spl deg/C, even though T/sub R-T/ was found to be only half the value at /spl sim/160/spl deg/C. Single crystals in the novel BiScO/sub 3/-PbTiO/sub 3/ system offer significantly higher T/sub c/s > 400/spl deg/C, while exhibiting electromechanical coupling coefficients k/sub 33/ > 90% being nearly constant till the T/sub R-T/ temperature around 350/spl deg/C, which greatly increases the temperature range for transducer applications.     

Field-induced strain behavior for potassium sodium bismuth titanate ceramics

Data are reported for the dielectric, piezoelectric, electrostrictive, and ferroelectric properties of potassium-substituted sodium bismuth titanate, [(K(x)Na(1-x))(0.5)Bi(0.5)]TiO3. For the morphotropic phase boundary composition x = 0.2, relaxor-type behavior was observed at room temperature with piezoelectric (effective d(333) = 325 x 10(-12) m/V) and ferroelectric properties (P(R) = 25 microC/cm(2), E(C) = 30 kV/cm). A transition to a relatively frequency-independent, diffuse phase transformation region occurred with increasing temperature, with no remanent strain or coercive field. Above the transition temperature, the field-induced strain was consistent with contributions from electrostriction and field induced piezoelectricity (M(3333) = 1.9 x 10(-16) m2/V2 and d333 = 81 x 10(-12) m/V at 100 degrees C). Information is given for the temperature dependence of properties, e.g., 0.14% strain induced at 50 kV/cm at 200 degrees C. Higher potassium content x = 0.6 stabilized the ferroelectric piezoelectric region to temperatures above 200 degrees C, with a relatively stable d(333) = 150-145 x 10-12 m/V between 25 degrees C and 200 degrees C. Pb-free KNBT ceramics appear competitive with PZT, especially for higher temperature electromechanical applications.     

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.     

Na1/2Bi1/2TiO3-BaTiO3系陶瓷压电性?及弛豫相变研究

系统研究了（１－ｘ）Ｎａ１／２Ｂｉ１／２ＴｉＯ３－ｘＢａＴｉＯ３（ｘ＝０．０２、０．０４、０．０６、０．０８、０．１０）无铅压电陶瓷系统的相界、材料压电性能,弛豫特性及相变．这个系统的陶瓷材料具有Ｋｔ／Ｋｐ较大,频率常数比较高等特点．Ｘ－ｒａｙ衍射结构分析发现此系统的相界在０．０４＜ｘ＜０．０６之间;材料的一些主要性能在相界附近达到极值．利用介电系数－温度曲线,并结合热激电流曲线对此系统的弛豫性进行研究和分析;初步研究了各配方组成的铁电－顺电的相变过程,发现在一定的组成范围内,材料在由铁电相向顺电相的转变过程中经历了一个过渡相区．     

新型钙钛矿型铁电陶瓷BSPT研究进展

(1-x)BiScO3-xPbTiO3(BSPT)是一种新型钙钛矿型结构的铁电体.BSPT体系在x=0.64附近有三方相和四方相的准同型相界(MPB).BSPT陶瓷的制备主要采用传统的电子陶瓷制备方法,包括常压法和高压法.BSPT陶瓷具有优良的介电和压电性能,居里温度Tc比Pb(Zr,Ti)O3(PZT)的高.综述了近年来对BSPT陶瓷的研究进展,重点介绍了邻近MPB的0.36BiScO3-0.64PbTiO3铁电陶瓷的性能.同时还介绍了掺杂对BSPT陶瓷的影响.     

无铅BaTiO_3系热敏电阻及其PTC性能的研究进展

通常在BaTiO3中固溶PbTiO3来提高BaTiO3系PTCR的居里温度,但是铅的毒性和挥发性限制了BaTiO3系PTCR的应用,因此需要研制出高居里点的无铅PTCR陶瓷。随着BNT、BKT含量增加,BaTiO3系PT-CR的居里点升高,但同时室温电阻快速增大。若在提高居里点的同时抑制室温电阻率的增大,就能制备出有实用价值的无铅高居里点的PTC材料。综述了BNT、BKT的含量对居里温度的影响及其机理,通过加入还原剂或在还原气氛下烧结并制定合理的烧结制度可以得到低室温电阻率和性能较好的PTC材料。     

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.     

Morphotropic phase boundary in Pb(Sc1/2Nb1/2)O3-BiScO3-PbTiO3 high temperature piezoelectrics

The solid solutions in the 0.36BiScO₃-0.64(1 − x)PbTiO₃-0.64xPb(Sc_1/2Nb_1/2)O₃ system were fabricated using wolframite precursor method. A coexistence of rhombohedral and tetragonal phases is formed in the studied compositions range and a wide morphotropic phase boundary region is confirmed by X-ray diffraction results. After the addition of Pb(Sc_1/2Nb_1/2)O₃, a relaxor behavior is induced and the dielectric maximum temperature shifts to higher temperatures with increasing measuring frequencies. The presence of relaxor can be ascribed to the formation of polar nanoregions. The studied composition exhibits the optimal ferroelectric and piezoelectric properties with d₃₃ of 453 pC/N and K_p of 0.58, T_m of 405 °C for x = 0.10 composition, which is suitable for future high-temperature piezoelectric application.     

Identification of the morphotropic phase boundary in the lead scandium tantalate–lead titanate solid solution system

A morphotropic phase boundary between rhombohedral and tetragonal phase regions has been identified to lie in the composition range x=0.4–0.45 by means of X-ray diffraction, and dielectric, pyroelectric, and piezoelectric measurements. Some curvature to this boundary at high temperatures is indicated in the temperature dependences of the dielectric constants and pyroelectric coefficients of poled specimens. This revised version was published online in November 2006 with corrections to the Cover Date.     

Measurements along the growth direction of PMN-PT crystals: dielectric, piezoelectric, and elastic properties

Property measurements are reported for Pb(Mg1/3Nb2/3)03-PbTiO3 (PMN-PT) single crystals grown along (001) by a seeded-melt method. Chemical segregation occurs during crystal growth, leading to property changes along the growth direction. Variations in dielectric, piezoelectric, and elastic properties were evaluated for specimens selected from the crystals. Room-temperature data are correlated with Tc and composition that ranged from 27 to 32% PT, i.e., in the vicinity of the morphotropic phase boundary (MPB). While there was little change in the high electromechanical coupling factor k33 (0.87-0.92), both the piezoelectric charge coefficient d33 (1100-1800 pC/N) and the free dielectric constant K3 (4400-7000) were found to vary significantly with position. Increases in d33 and KT33 were relatively offsetting in that the ratio yielded a relatively stable piezoelectric voltage coefficient g33 (27-31 x 10(-3) Vm/N). Values are also reported for the elastic compliance (3.3-6.3 x 10(-11) m2/N) determined from resonance measurements. Enhancements in d33 and K(T)33 were associated with lattice softening (increasing sE33) as the composition approached the MPB. Details are reported for the piezoelectric, dielectric, and elastic properties as a function of growth direction, Tc, and composition. The results are useful for an understanding of properties in PMN-PT crystals and for the design of piezoelectric devices.     

Dielectric and piezoelectric properties in the lead-free system Na0.5K0.5NbO3-BiScO3-LiTaO3

Phase relations, dielectric and piezoelectric properties are reported for the ternary system 98%[(1 - x) (Na(0.5)K(0.5)NbO(3))-x(LiTaO(3))]-2%[BiScO(3)] for compositions x ≤ 10 mol% LiTaO(3). The phase content at room-temperature changed from mixed phase, monoclinic + tetragonal, for unmodified 98%(Na(0.5)K(0.5)NbO(3))-2%(BiScO(3)), to tetragonal phase for compositions >2 mol% LiTaO(3). Curie peaks at 360 to 370°C were observed for all compositions, but peaks became diffuse at x ≥ 3 mol%, and two dielectric peaks, at 370 and 470°C, were observed for 5 mol% LiTaO(3). Phase segregation, and finite size affects associated with the core-shell structure, account for the occurrence of two dielectric peaks in 5 mol% LiTaO(3), and diffuse dielectric behavior. The value of d(33) piezoelectric charge coefficient increased from ~160 pC/N for 0 mol% LiTaO(3) to 205 to 214 pC/N for 1 to 2 mol% LiTaO3 solid solutions, before falling sharply at 3 mol% LiTaO(3). TEM-EDX analysis revealed core-shell grain structures with segregation of Bi, Sc, and Ta in the outer ~100-nm shell of the 5 mol% LT sample.     

Epitaxial growth of PbTiO(3) films on SrTiO(3) by RF magnetron sputtering

Epitaxial growth of PbTiO(3) films on (100)SrTiO(3 ) single crystal plates is investigated in detail for piezoelectric device applications. PbTiO(3) films were prepared by RF magnetron sputtering at relatively low temperature and subsequently annealed. The films had a perovskite structure under a wide annealing temperature range. Epitaxial growth of PbTiO(3) films on SrTiO (3) single crystal was achieved, although there was a limitation in the maximum film thickness (<0.3 mum). A thicker film (>0.6 mum) was successfully obtained by high-temperature sputtering. Lateral overgrowth of PbTiO(3) film was attempted using a high-temperature sputtering technique. A TEM micrograph confirms that PbTiO(3) film was epitaxially grown on SrTiO(3) single crystal and overgrown laterally to cover a Pt electrode film. To characterize film quality, ferroelectric properties are investigated. The electromechanical coupling constant of the PbTiO(3) film was evaluated by analyzing impedance characteristics, and was found to be as large as 0.8.     

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.     

Depolarization temperature and piezoelectric properties of Na1/2Bi1/2TiO3-Na1/2Bi1/2(Zn1/3Nb2/3)O3 ceramics by two-stage calcination method

A new group of NBT-based lead-free piezoelectric ceramics, Na_1/2Bi_1/2TiO₃-Na_1/2Bi_1/2(Zn_1/3Nb_2/3)O₃, was synthesized using the two-stage calcination method and depolarization temperatures and piezoelectric properties were also investigated. The XRD analysis showed that the ceramics system had a morphotropic phase boundary (MPB) between the rhombohedral and the tetragonal structure. The highest piezoelectric properties of d ₃₃ = 97 pC/N and k _t = 0·46 were obtained near MPB compositions. Furthermore, the depolarization temperatures near MPB compositions were slightly decreased and the lowest T _d was maintained at 210°C.     

Piezoelectric properties in (K0.5Bi0.5)TiO 3-(Na0.5Bi0.5)TiO3-BaTiO 3 lead-free ceramics

Lead-free piezoelectric ceramics with compositions around the morphotropic phase boundary (MPB) x(Na_0.5Bi_0.5)TiO _3-y(K_0.5Bi_0.5)TiO₃-zBaTiO ₃ [x + y + z = 1; y:z = 2:1] were synthesized using conventional, solid-state processing. Dielectric maximum temperatures of 280degC and 262degC were found for tetragonal 0.79(Na_0.5Bi_0.5)TiO₃-0.14(K_0.5 Bi_0.5)TiO₃-0.07BaTiO$ d3 (BNBK79) and MPB composition 0.88(Na_0.5Bi_0.5)TiO₃-0.08(K _0.5Bi_0.5)TiO₃-0.04BaTiO$ d3 (BNBK88), with depolarization temperatures of 224degC and 162degC, respectively. Piezoelectric coefficients d₃₃ were found to be 135 pC/N and 170 pC/N for BNBK79 and BNBK88, and the piezoelectric d₃₁ was determined to be -37 pC/N and -51 pC/N, demonstrating strong anisotropy. Coercive field values were found to be 37 kV/cm and 29 kV/cm for BNBK79 and BNBK88, respectively. The remanent polarization of BNBK88 (~40 muC/cm²) was larger than that of BNBK79 (~29 muC/cm²). The piezoelectric, electromechanical, and high-field strain behaviors also were studied as a function of temperature and discussed     

Dielectric and piezoelectric properties of PbFe1/2Nb1/2O3-PbTiO3 ceramics from the morphotropic phase boundary compositional range

Dielectric, X-ray, and piezoelectric studies of highly-resistive Li-doped (1-x)PbFe(1/2)Nb(1/2)O(3)-(x)PbTiO(3) (PFN-xPT) ceramics from the 0 ≤ x ≤ 0.2 range fabricated by solid-state synthesis and usual sintering have been carried out. Distinct anomalies of dielectric and piezoelectric parameters, corresponding to the transition between rhombohedral (monoclinic) and tetragonal ferroelectric phases, have been observed in pure PFN and PFN-xPT compositions with PbTiO(3) content up to 8 mol.%. The x,T-phase diagram of the PFN-xPT solid solution system has been constructed using these data.     

Na1/2Bi1/2TiO3-BaTiO3系陶瓷压电性及弛豫相变研究

系统研究了（１－ｘ）Ｎａ１／２Ｂｉ１／２ＴｉＯ３－ｘＢａＴｉＯ３（ｘ＝０．０２、０．０４、０．０６、０．０８、０．１０）无铅压电陶瓷系统的相界、材料压电性能、驰豫特性及相变。这个系统的陶瓷材料具有Ｋｔ／Ｋｐ较大,频率常数比较高等特点,Ｘ－ｒａｙ衍射结构分析发现此系统的相界在０．０４〈ｘ〈０．０６之间;材料的一些主要性能在相界附近达到极值。利用介电系数－温度曲线,并结合热激电流曲线对此系统的驰豫性进