La2O3掺杂(Na0.5Bi0.5)0.94Ba0.06TiO3无铅压电陶瓷的介电弛豫研究

采用固相合成法制备了La2O3掺杂(Na0.5Bi0.5)0.94Ba0.06TiO3无铅压电陶瓷.研究了La2O3掺杂对(Na1/2Bi1/2)TiO3陶瓷晶体结构、介电性能与介电弛豫行为的影响.XRD分析表明,在所研究的组成范围内陶瓷材料均能够形成纯钙钛矿固溶体.材料的介电常数-温度曲线显示陶瓷具有两个介电反常峰Tf和Tm.修正的居里-维斯公式较好的描述了陶瓷弥散相变特征,弥散指数随La2O3掺杂量的增加而增加.掺杂量较低的陶瓷仅在低温介电反常峰Tf附近表现出明显的频率依赖性,随掺杂量的增加,陶瓷材料在室温和低温介电反常峰Tf之间都表现出明显的频率依赖性.并根据宏畴-微畴转变理论探讨了该体系陶瓷介电弛豫特性的机理.     

补偿电价取代对(Bi1/2Na1/2)TiO3无铅压电陶瓷介电与压电性能的影响

采用传统陶瓷制备方法,制备出一种钙钛矿结构无铅新压电陶瓷材料(1-x)(Bi1/2Na1/2)TiO3-xBi(Mg2/3 Nb1/3)O3.研究了一种化合物Bi(Mg2/3 Nb1/3)O3中两种离子Bi3 和(Mg2/3Nb1/3)3 同时进行补偿电价取代对(Bi1/2Na1/2)TiO3陶瓷介电和压电性能的影响.X射线衍射分析表明,所研究的组成均能够形成纯钙钛矿(ABO,)型固溶体.陶瓷材料的介电常数-温度曲线显示该体系材料具有明显的弛豫铁电体特征.适量的取代能提高材料的压电性能,在x=0.7%时压电常数d33=94 pC/N,x=0.9%时厚度机电耦合系数kt=0.46,为所研究组成中的最大值.该体系陶瓷具有较大的kt值和较小的kp值,具有较大的各向异性.     

（Bi1/2Na1/2）0.94Ba0.06TiO3无铅压电陶瓷制备工艺研究

采用两步合成工艺制备了（Bi1/2Na1/2）0.94Ba0.06TiO3无铅压电陶瓷。利用XRD、SEM等分析技术，研究了（Bi1/2Na1/2）0.94Ba0.06TiO3陶瓷的先低温再高温的两步合成工艺，烧结工艺对陶瓷晶体结构和压电性能的影响。结果表明，两步合成工艺有利于提高陶瓷性能，其压电常数如3最大值可达155pC/N，比传统方法提高了24％。较合适的预合成工艺为：750℃/1h＋8501000℃/2～3h；该体系陶瓷具有较宽的烧结温度范围，较合适的烧结工艺为：1150～1190℃/2～3h。     

（Na1/2Bi1/2）TiO3无铅压电陶瓷的复合离子与补偿电价取代效应研究

采用传统陶瓷制备方法，制备出两种钙钛矿结构无铅新压电陶瓷材料（1-x）（Na1/2Bi1/2）TiO3-x（Na1/2Bi1/2）（Sb1/2Nb1/2）O3和（1-y）（Na1/2Bi1/2）TiO3-yBi（Mg2/3Nb1/3）O3。研究了复合离子与补偿电价取代对（Na1/2Bi1/2）TiO3陶瓷晶体结构和压电性能的影响。）（射线衍射分析表明，在所研究的组成范围内两种陶瓷材料均能够形成纯钙钛矿固溶体．陶瓷材料的介电常数-温度曲线显示两种陶瓷体系具有明显的弛豫铁电体特征．适量的复合离子与补偿电价取代都能提高材料的压电性能，在工=0．8％时，陶瓷的压电常数d33=97pC/N，厚度机电耦合系数kr=0．50，在y=0．7％时d33=94pC/N，y=0．9％时k1=0．46，为所研究组成中的最大值。两种陶瓷体系都具有较大的‰值和较小的kp值，具有较大的各向异性，是一种优良的、适合高频下使用的超声换能材料．     

Y2O3掺杂(Bi0.5Na0.5)0.94Ba0.06TiO3无铅压电陶瓷的研究

采用固相合成法制备了Y2O3掺杂(Bi0.5 Na0.5)0.94 Ba0.06 TiO3无铅压电陶瓷.研究了Y2O3掺杂对(Bi0.5 Na0.5)0.94Ba0.06 TiO3陶瓷晶体结构、介电与压电性能的影响.XRD分析表明,在所研究的组成范围内陶瓷均能够形成纯钙钛矿固溶体.介电常数-温度曲线显示陶瓷具有弛豫铁电体特征,陶瓷的弛豫特征随掺杂的增加更为明显.在Y2O3掺杂量为0.5%时陶瓷的压电常数d33分别为137 pC/N,为所研究组成中的最大值,掺杂量为0.1%时,机电耦合系数kp与kt最大值为0.30,0.47.     

Bi0.5Na0.5 TiO3基无铅压电陶瓷应用的研究进展

随着人们环保意识的增强,作为环境友好型的无铅压电陶瓷典型代表Bi0.5Na0.5TiO3基压电陶瓷已成为压电陶瓷领域研发的热点材料之一.结合目前有关报道,着重介绍了近年来国内外该陶瓷在相关电子器件中的应用,并展望了BNT基无铅压电陶瓷应用的发展趋势.     

Y2O3掺杂（Bi0．5Na0．5）0．94Ba0．06TiO3无压电陶瓷的研究铅

采用固相合成法制备了Y2O3掺杂（Bi0．5Na0．5）0．94Ba0．06TiO3无铅压电陶瓷。研究了Y2O3掺杂对（Bi0．5Na0．5）0．94Ba0．06TiO3陶瓷晶体结构、介电与压电性能的影响。XRD分析表明,在所研究的组成范围内陶瓷均能够形成纯钙钛矿固溶体。介电常数-温度曲线显示陶瓷具有弛豫铁电体特征,陶瓷的弛豫特征随掺杂的增加更为明显。在Y2O3掺杂量为0．5％时陶瓷的压电常数d33分别为137pC／N,为所研究组成中的最大值,掺杂量为0．1％时,机电耦合系数kp与kt最大值为0．30,0．47。     

(Bi0.5Na0.5)1-x(BaaSrb)x TiO3无铅压电陶瓷体系的设计、制备与性能

综合考虑(Bi0.5Na0.5) TiO3(BNT)基无铅压电陶瓷的A-位、B-位原子的原子量差、离子半径差和电负性差,提出了一种BNT基无铅压电陶瓷的设计方法.依据BNT基无铅压电陶瓷所报道的相关数据,定义了ABO3型压电陶瓷的综合因子F(w)为 F(w)= M+R+100X,式中,M为A-位和B-位离子的质量差,R为A-位和B-位离子的离子半径差,X为A-位和B-位离子的电负性差.研究发现,F(w)与BNT基无铅压电陶瓷的压电耦合系数k33和kp, 以及压电常数d33有非常紧密的关系.根据该方法设计了(Bi0.5Na0.5)1-x(BaaSrb)xTiO3无铅压电陶瓷新体系,并申报了国家发明专利.研究结果表明,该体系压电陶瓷具有很好的工艺特性和压电响应,高的压电常数,其机电耦合系数kp为0.311,压电常数d33高达146pC/N,居里温度Tc为310℃,是一种很有实际应用前景的新型压电陶瓷材料体系.     

掺La3+对0.94(Na1/2Bi1/2)TiO3-0.06BaTiO3陶瓷介电行为和压电性能的影响

对(Bi1／2Na1／2)TiO3-BaTiO3压电陶瓷在准同型相界处的组成掺入不同量的La^3 ,研究掺杂对于体系结构、压电与介电性能的影响．结果表明,掺杂使得体系的弛豫铁电体特征更为明显,相变的弥散程度增大,室温下的介电常数增大;当掺杂量低于1．5％时,材料的d33值增大,但同时介电损耗也相对于基体有所增加．当掺杂量达到3％以后,陶瓷的压电性能严重降低．     

(Na0.5Bi0.5)TiO3基无铅压电陶瓷研究进展

综述了（Na0.5Bi0.5)Tio3（简写为NBT）基无铅压电陶瓷的发展现状,特性及影响因素,用分子轨道理论解释了NBT强铁电性的成因,对研究较多的三个体系：NBT-ATiO3(A=Ca,Sr,Ba),NBT-BNbO3(B=Na,K)和NBT－Ln掺杂体系给予了概括介绍,内容包括成分配比,性能和应用,并提出了NBT基无铅压电陶瓷的设计原则。     

Dielectric and piezoelectric properties of (0.97-x) Bi1/2Na1/2TiO3-xBi1/2K1/2TiO3-0.03NaNbO3 ceramics

Ceramics of the series (0.97-x)Bi_1/2Na_1/2TiO₃-xBi_1/2K_1/2TiO₃-0.03NaNbO₃ (x = 0, 0.02, 0.06, 0.10, 0.16, 0.20, 0.30) were prepared by the conventional mixed oxide method. Influence of Bi_1/2K_1/2TiO₃ content on the crystal structure, microstructure, dielectric and piezoelectric properties were studied. All compositions showed single perovskite phase and the morphotropic phase boundary (MPB) between rhombohedral and tetragonal phase existed at the point of x = 0.16. Temperature dependences of permittivity and dissipation factor of unpoled samples revealed that permittivity increased with Bi_1/2K_1/2TiO₃ content and it reached maximum value near the MPB. At the same time, the peak value of dissipation factor increased with the addition of Bi_1/2K_1/2TiO₃. All the samples experienced two phase transitions: from ferroelectric to antiferroelectric at the first transition temperature (T_d) and from antiferroelectric to paraelectric at the temperature (T_m) corresponding to maximum value of permittivity. The phase transition from ferroelectric to antiferroelectric had relaxor characteristic and T_d shifted to lower temperature while increasing Bi_1/2K_1/2TiO₃ content. The best piezoelectric properties were obtained in 0.81Bi_1/2Na_1/2TiO₃-0.16Bi_1/2K_1/2TiO₃-0.03NaNbO₃ ceramic with a piezoelectric constant (d₃₃) of 146pC/N, planar electromechanical coupling factor (k_p) of 30.3% and thickness electromechanical coupling factor (k_t) of 53.2%. Abnormal piezoelectric properties were observed in the sample (x = 0.20), which was attributed to the co-existence of ferroelectric and antiferroelectric phases in it.     

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.     

(Bi1/2Na1/2)TiO3 additive effect for improved piezoelectric and mechanical properties in PZT ceramics

Bismuth sodium titanate, (Bi_1/2Na_1/2)TiO₃(BNT) additive effect for the improvement of piezoelectric and mechanical properties in PZT ceramics were discussed from the viewpoint of high-power applications. The addition of 5 wt% BNT in Pb(Zr_0.52Ti_0.48)O₃ ceramics showed suppressive effect for electro-mechanical coupling factor (k _p) value. On the other hand, the addition of 0.5 and 1.0 wt% BNT contributed to improve the four point mechanical bending strength when it was sintered at 1150°C.     

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.     

Lead-free piezoelectric ceramics with composition of (0.97−x)Na1/2Bi1/2TiO3-0.03NaNbO3-xBaTiO3

Compositions in (Na_1/2Bi_1/2)TiO₃ based ternary system, (0.97 – x) (Na_1/2Bi_1/2)TiO₃-0.03NaNbO₃-xBaTiO₃ (x = 0, 0.01, 0.02, 0.04, 0.05, 0.06, 0.08) are synthesized using conventional solid state reaction method. Influence of BaTiO₃ on crystal structure, dielectric and piezoelectric properties are investigated. All compositions can form single perovskite phase. Powder x-ray diffraction patterns can be indexed assuming a pseudo-cubic structure. Lattice constant increases with the increase of BaTiO₃ concentration. Rhombohedral distortion is observed in poled samples with BaTiO₃ concentration up to 6 mol%. Temperature dependence of dielectric constant and dissipation factor measurement reveals that all compositions experience two phase transitions: from ferroelectric to antiferroelectric and from antiferroelectric to paraelectric. Both transition temperatures, T _c and T _f, are lowered due to introduction of BaTiO₃. Ferroelectric to antiferroelectric phase transition has relaxor characteristics. Piezoelectric properties have relatively higher value around 1 mol% to 4 mol% BaTiO₃. In ceramics with x = 0.02, thickness electromechanical coupling factor (k _t) of 0.51 and piezoelectric charge constant (d ₃₃) of 110 × 10^–12 C/N are obtained. Addition of small amount of BaTiO₃ (x = 0.01, 0.02) improves piezoelectric properties compared to NBT-NN binary system, while T _f remains above 140°C, higher than that of NBT-BT binary system composition with similar piezoelectric properties. This is in favor of the possible application of them as lead-free piezoelectric ceramics.     

Quenching-induced nonergodicity in ergodic Na1/2Bi1/2TiO3–BaTiO3–AgNbO3 ceramics

Quenching from sintering temperature enhances the depolarization temperature (T_d) in Na_1/2Bi_1/2TiO₃-based ceramics without significant deterioration of piezoelectric properties (d₃₃). In this work, quenching effects in an ergodic relaxor 0.97(0.94Na_0.5Bi_0.5TiO₃–0.06BaTiO₃)–0.03AgNbO₃ (NBT–6BT–3AN) were investigated based on structure, ferroelectric, and dielectric properties. The ergodicity to nonergodicity transition was obtained by quenching NBT–6BT–3AN above 1000 °C. The temperature stability of the quenching-induced nonergodicity was examined by annealing the quenched sample at 300 °C and 600 °C. The effect of oxygen vacancy on ergodicity to nonergodicity transition was investigated by comparing ferroelectric and electrostrain responses of the quenched and nitrogen-atmosphere-annealed samples. The influence of quenching on the structure including the average crystal structure, phase fraction and lattice distortion and the local structure including bond lengths and ordering of ions was analyzed. The ergodicity to nonergodicity transition upon quenching is ascribed to the contribution of the off-centered Bi³⁺ ions and ordered local structure.

Graphical abstract

     

Structure and electrical properties of Bi0.5Na0.5TiO3-Y0.5Na0.5TiO3-BaTiO3 lead-free piezoelectric ceramics

New (1 – x ? y)Bi_0.5Na_0.5TiO₃-xY_0.5Na_0.5TiO₃-yBaTiO₃ lead-free ceramics have been prepared by a conventional ceramic fabrication technique, and their structure and electrical properties have been studied. A morphotropic phase boundary (MPB) of rhombohedral and tetragonal phases is formed at 0.04 < y < 0.10. As compared to pure Bi_0.5Na_0.5TiO₃ ceramic, the partial substitutions of Y³⁺ for Bi³⁺ and Ba²⁺ for (Bi_0.5Na_0.5)²⁺ in the A-sites of Bi_0.5Na_0.5TiO₃ lower effectively the coercive field E _c and increase the remanent polarization P _r of the ceramics. Because of low E _c, large P _r and the MPB, the ceramics with x = 0–0.02 and y = 0.06 exhibit the optimum piezoelectric properties: d ₃₃ = 155–159 pC/N and k _p = 28.8–36.7%. The temperature dependences of dielectric properties of the ceramics show relaxor-like behaviors. The ferroelectric properties at different temperature suggest that the ceramics may contain both the polar and non-polar regions near/above T _d.     

Dielectric and microwave properties study of TiFeNbO6 ceramics added Bi2O3

In this paper the ceramic matrix of TiFeNbO₆ (TFNO) was studied. The TFNO phase was calcined at 1,075 °C and used to prepare the samples, of 2, 4, 6, 8 and 10 wt% of the Bi₂O₃ and sintered at 1,125 °C. These samples were characterized by X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy and dielectric microwave properties. XRD and RS were used to characterize these samples. The samples presented two new phases. The first phase is the tetragonal rutile structure with a space group of P4₂/mnm, equivalent at parent rutile Ti_0.4Fe_0.3 Nb_0.3O₂ (TFNO) with 040725 ICSD code, and the secondary phase belonging to the pyrochlore system Bi_1.721Fe_1.056Nb_1.134O₇ (BFNO), with a space group of Fd-3mZ (227), in a cubic structure. The dielectric properties have shown significant variation for 10 % Bi₂O₃-added sample, because the formation of the new phase (BFNO) contributes with the reduction of τ _f from 281.12 to 77.45 ppm/°C and with increase in ε _r , from 47.23 to 63.77 and an increase in the dielectric loss (tan δ), from 0.0016 to 0.0068, respectively. Even though, Bi₂O₃ additive deteriorates the dielectric loss of the ceramics, the permittivity has enhanced significantly, which is advantageous for reduction of the air gap between the probe and the DRA antennas that influences on the samples for future application in microwave.     

Effect of substitution of titanium by magnesium and niobium on structure and piezoelectric properties in (Bi1/2Na1/2)TiO3 ceramics

To develop new (Bi_1/2Na_1/2)TiO₃-based ceramics with excellent piezoelectric properties, the similarities and the differences between PZT and (Bi_1/2Na_1/2)TiO₃ ceramics were analysed. Based on the analysis, a new (Bi_1/2Na_1/2)TiO₃-based piezoelectric ceramic of B-site substitution of complex ions (Mg_1/3Nb_2/3)⁴⁺ for Ti⁴⁺ was prepared by a conventional ceramic technique, and the effect of complex ions (Mg_1/3Nb_2/3)⁴⁺ addition on the microstructure, dielectric and piezoelectric properties was investigated. The research results show that all compositions are mono-perovskite phase and the grain size increases with increasing content of (Mg_1/3Nb_2/3)⁴⁺. The piezoelectric constant d ₃₃ first increases and then decreases, and electromechanical coupling factor k _p varies insignificantly with increasing content of (Mg_1/3Nb_2/3)⁴⁺.