BaNb2O6掺杂Na1/2Bi1/2TiO3无铅压电陶瓷的介电弛豫

采用传统陶瓷制备方法,制备了无铅新压电陶瓷材料Na1/2Bi1/2TiO3-xBaNb2O6.研究了BaNb2O6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,修正的居里一外斯公式较好的描述了陶瓷弥散相变特征,弥散指数随BaNb2O6掺杂量的增加而增加.该体系陶瓷表现出与典型弛豫铁电体明显不同的弛豫行为,低掺杂量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,而高掺杂的陶瓷材料在室温和Tf之间都表现出明显的频率依赖性.并根据宏畴一微畴转变理论探讨了该体系陶瓷产生介电弛豫的机理.     

Na-Ni掺杂对Bi_2(Zn_(1/3)Nb_(2/3))_2O_7陶瓷性能的影响

采用传统固相反应法制备Bi_2(Zn_(1/3)Nb_(2/3))_2O_7基陶瓷.研究Na~+、Ni~(2+)分别替代Bi~(3+)、Nb~(5+)对Bi_2(Zn_(1/3)Nb_(2/3))_2O_7陶瓷烧结特性和介电性能的影响.替代后样品的烧结温度从960℃降低到870℃左右.在-30℃～+130℃,陶瓷样品的温谱中出现明显的介电弛豫现象,弛豫峰所在温区较宽;当Ni~(2+)替代量增加到0.2时出现双弛豫峰.随着Ni~(2+)替代量增加,弛豫峰值温度向高温移动,弛豫激活能增加,两弛豫峰之间距增加.用缺陷偶极子和晶格畸变解释了Na-Ni掺杂Bi_2(Zn_(1/3)Nb_(2/3))_2O_7的介电弛豫现象.     

A位复合铁电陶瓷Bi0.5(Na0.82K0.18)0.5TiO3-BiCrO3的介电弛豫

采用固相反应法制备了A位复合铁电陶瓷(1-x)Bi_0.5(Na_0.82K_0.18)_0.5TiO₃-xBiCrO₃(BNKT-BCx). 研究了该陶瓷在室温至500℃温度范围内的介电性能. 结果表明该陶瓷的介电温谱存在两个介电反常峰和一个介电损耗峰, 低温介电反常峰温度附近具有明显的介电常数频率依赖性, 但居里峰随频率增加基本不变, 与典型弛豫铁电体的特征不同. 将弛豫铁电体分为本征弛豫和非本征弛豫铁电体, 通过分析极化前和极化后陶瓷的介电温谱, 发现该体系低温介电反常峰温度附近的介电频率依赖性为空间电荷和缺陷偶极子极化引起的非本征弛豫.     

B位离子部分取代和Fe/Nb比改变对Pb(Fe_(1/2)Nb_(1/2))O_3陶瓷介电弛豫性能的影响

对 Pb(Fe_(1/2)/Nb_(1/2))O_3铁电陶瓷进行了 B 位离子部分取代和改变 Fe/Nb 比对介电性能、介电弛豫性能影响的研究,发现当它的 B 位 B_1、B_2离子比偏离于1:1时,其 K_(max)的频率弥散变明显(即△T_(0.1-100kHz)>0°),这可能是在有序-无序基本弛豫极化基础上产生了附加的空间电荷弛豫极化,它对弛豫铁电体的介电弛豫性质起着一定贡献。     

Pb(Ni1/3Nb2/3)O3-PbTiO3系统准同型相界附近的介电异常

用两步合成法制备了(1-x)Pb(Ni1/3Nb2/3)O3-xPbTiO3(x=0.300.40)陶瓷,对其相结构和介电性能进行了研究. XRD分析表明,准同型相界在PT含量x=0.340.38范围内. 介电性能研究结果表明,组成在准同型相界处的试样, 其介电常数呈现最大值.同时还发现,准同型相界处的陶瓷出现介电双峰,其中一个为弛豫型?铁电相向顺电相转变的相变峰;另一个介电峰处于130150C的高温区, 可能是由镍离子变价、相结构变化等缺陷引起的松弛极化产生的.     

A位复合铁电陶瓷Bi0.5(Na0.82K0.18)0.5TiO3-BiCrO3的介电弛豫

采用固相反应法制备了A位复合铁电陶瓷(1-x)Bi_0.5(Na_0.82K_0.18)_0.5TiO₃-xBiCrO₃(BNKT-BCx). 研究了该陶瓷在室温至500℃温度范围内的介电性能. 结果表明该陶瓷的介电温谱存在两个介电反常峰和一个介电损耗峰, 低温介电反常峰温度附近具有明显的介电常数频率依赖性, 但居里峰随频率增加基本不变, 与典型弛豫铁电体的特征不同. 将弛豫铁电体分为本征弛豫和非本征弛豫铁电体, 通过分析极化前和极化后陶瓷的介电温谱, 发现该体系低温介电反常峰温度附近的介电频率依赖性为空间电荷和缺陷偶极子极化引起的非本征弛豫.     

NiO/La2Mo2O9介电和表面势研究

固体氧化物燃料电池(SOFC)阳极材料得失电子能力和氧扩散性能影响其催化性能。对NiO体积含量分别为20%和40%的NiO/La2Mo2O9复合材料(N/L28和N/L46)的介电行为以及得失电子能力进行了研究。N/L28和N/L46样品的介电温度谱中按照损耗峰出现的温度从低到高的顺序依次发现与NiO相和La2Mo2O9相氧短程扩散有关的损耗峰,833K处观察到的介电损耗的突变与αLa2Mo2O9-βLa2Mo2O9相变有关。N/L46样品在500~813K范围内的一个宽化的损耗峰可用一个具有弛豫性质的峰和两个非弛豫性质的峰进行拟合。表面势测量结果表明,样品失去电子所需能量由大到小的顺序为La2Mo2O9,N/L28,N/L46,NiO。     

NiO/La2Mo2O9介电和表面势研究

固体氧化物燃料电池(SOFC)阳极材料得失电子能力和氧扩散性能影响其催化性能。对NiO体积含量分别为20%和40%的NiO/La2Mo2O9复合材料(N/L28和N/L46)的介电行为以及得失电子能力进行了研究。N/L28和N/L46样品的介电温度谱中按照损耗峰出现的温度从低到高的顺序依次发现与NiO相和La2Mo2O9相氧短程扩 散有关的 损耗峰,833K处 观 察 到 的 介 电 损 耗 的 突 变 与αLa2Mo2O9-βLa2Mo2O9相变有关。N/L46样品在500~813K范围内的一个宽化的损耗峰可用一个具有弛豫性质的峰和两个非弛豫性质的峰进行拟合。表面势测量结果表明,样 品 失 去 电 子 所 需 能 量 由 大 到 小 的 顺 序 为La2Mo2O9,N/L28,N/L46,NiO。     

La2O3掺杂（Na0．5 Bi0．5）0．94 Ba0.06 TiO3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.     

铌酸锶钡铁电陶瓷的介电弛豫行为

铌酸锶钡Sr_1－xBa_xNb₂O₆（0．25＜x＜075）陶瓷固溶体是典型的钨青铜结构弛豫型铁电体,其介电行为与钙钛矿结构弛豫型铁电体的介电行为极为相似,即射频介电温谱呈现弥散的居里温区.通过对Sr_1－xBa_xNb₂O₆（x＝0．4、0.5、06）在─170～＋400℃的介电温谱进行详细测定;与其热释电测量结果进行对比,发现它们在低温区的介电响应存在一个不同于钙钛矿结构弛豫型铁电体的弛豫过程,高于居里温区的介电响应很好地符合居里-外斯定律．结合钨青铜结构铁电体存在无公度相的特征,初步探讨了钨青铜结构弛豫型铁电体中局域极化的产生、增大和凝聚特点．     

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．     

掺钛铌镁酸铅铁电体的自发和场诱导相变

测试了掺钛铌镁酸铅系列铁电陶瓷介电和热释电温度梯,观察到自发和场诱导正常铁电体－驰豫型铁电体－顺电体相互转变的现象,在分析这一相变的特点和相应结构特征的基础上,提出了驰豫型铁电体钠米极性微区的动态结构模模型。     

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     

三元陶瓷Pb(In1/2Nb1/2)O3-Pb(Ni1/3Nb2/3)O3-PbTiO3准同型相界附近组分的介电、铁电和压电性能

铅基复合钙钛矿铁电材料广泛应用于机电传感器、致动器和换能器。二元铁电固溶体Pb(Ni_1/3Nb_2/3)O₃- PbTiO₃(PNN-PT)由于其在准同型相界(MPB)区域具有优异的压电、介电性能而备受关注。然而较大的介电损耗和较低的居里温度限制了其在高温高功率器件方面的应用。本研究通过引入Pb(In_1/2Nb_1/2)O₃ (PIN)作为第三组元改善PNN-PT的电学性能, 提高其居里温度; 通过两步法合成了MPB区域的三元铁电陶瓷Pb(In_1/2Nb_1/2)O₃- Pb(Ni_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PNN-PT), 研究了其结构、介电、铁电和压电性能。制备的所有组分陶瓷具有纯的钙钛矿结构。随着PT含量的增加, 陶瓷结构从三方相转变为四方相。通过XRD分析得到了室温下PIN-PNN-PT体系的MPB相图。体系的居里温度由于PIN的加入得到了很大的提高, 更重要的是PIN的引入降低了PNN-PT体系的介电损耗和电导。MPB处的组分展现出了优异的电学性能, 室温下, 性能最优组分为0.30PIN-0.33PNN-0.37PT: d₃₃=417 pC/N, T_C=200 ℃, ε′= 3206, tanδ=0.033, P_r=33.5 μC/cm², E_C=14.1 kV/cm。引入PNN-PT的PIN第三组元使得体系的居里温度和压电性得到提高的同时降低了的介电损耗和电导率, 因此, PIN-PNN-PT三元铁电陶瓷在高温高功率换能器等方面具备一定的应用潜力。     

Structure and electrical properties of (100)-oriented Pb(Zn1/3Nb2/3)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 thin films on La0.7Sr0.3MnO3 electrode by chemical solution deposition

(100)-oriented 0.462Pb(Zn_1/3Nb_2/3)O₃–0.308Pb(Mg_1/3Nb_2/3)O₃–0.23PbTiO₃ (PZN-PMN-PT) perovskite ferroelectric thin films were prepared on La_0.7Sr_0.3MnO₃/LaAlO₃ (LSMO/LAO) substrate via a chemical solution deposition route. The perovskite LSMO electrode was found to effectively suppress the pyrochlore phase while promote the growth of the perovskite phase in the PZN-PMN-PT film. The film annealed at 700 °C exhibited a high dielectric constant of 2130 at 1 kHz, a remnant polarization, 2P_r, of 29.8 μC/cm², and a low leakage current density of 7.2 × 10^− 7 A/cm² at an applied field of 200 kV/cm. The ferroelectric polarization was fatigue-free at least up to 10¹⁰ cycles. Piezoelectric coefficient, d₃₃, of 48 pm/V was also demonstrated. The results showed that much superior properties could be achieved with the PZN-PMN-PT thin films on the solution derived LSMO electrode than on Pt electrode by sputtering.     

Field-induced effect in the <111>-oriented 0.70Pb(Mg1/3Nb2/3)O3–0.30PbTiO3 single crystals

Temperature-dependent dielectric constant, X-ray diffraction(XRD), thermally stimulated discharging current (TSDC) and polarization hysteresis loops for <111>-oriented 0.70Pb(Mg_1/3Nb_2/3)O₃–0.30PbTiO₃ crystals after poling under different fields were measured. Comparing with unpoled sample during heating, except that there is a transition from the state of normal ferroelectric rhombohedral (macro-domain) to the state of relaxor ferroelectric rhombohedral (micro-domain) for the poled samples, it was found that no other phase transition was induced by poling fields. XRD showed that after poling the piezoelectric elongation of the unit cell occurred along the polar direction. It was suggested that an extra peak in the T–ε curve of poled sample around 105 °C is not only caused by a macro–micro domain transition but also caused by the depolarization process of 180° and 71° domain switching simultaneously.     

0-3/1-3混合连通型铁电陶瓷-铁电聚合物的热释电性

推导出了0-3/1-3混合连通型铁电陶瓷-铁电聚合物的热释电系数表达式, 并详细讨论了陶瓷体积分数 v₂和陶瓷颗粒粒径与膜厚比(G/t)分别对复合材料的热释电系数p_c及p_c/ε_c(ε_c为复合材料的介电常数)的影响。结果表明: 当G/t≥0.5时, 不同陶瓷体积分数复合材料的热释电系数p_c均趋向于某个定值, 说明此时G/t对热释电系数的影响可忽略不计; 另外当陶瓷体积分数为0.1时, 随着G/t的增大, p_c /ε_c出现一个极大值, 且当G/t=0.9时, p_c /ε_c比纯PZT陶瓷的大8倍, 表明此条件为最佳工艺条件。而且, 在低陶瓷体积分数和低G/t比时, 理论曲线与实验数据符合较好。      

Nb掺杂Bi4Ti3O12层状结构铁电陶瓷的电行为特性研究

采用固相烧结工艺制备了Nb⁵⁺掺杂的Bi₄Ti₃O₁₂层状结构铁电陶瓷.运用XRD 和AFM对Bi₄Ti_3-xNb_xO_12+x/2材料的微观结构进行表征,发现所制备的陶瓷均具有单一的正交相结构,抛光热腐蚀表面晶粒的显微形貌表现为随机排列的棒状结构.通过对材料直流电导率与温度关系的Arrhenius拟合,分析丁Bi₄Ti_3-xNb_xO_12+x/2的导电机理. Nb⁵⁺掺杂提高了材料的介电常数,但居里温度随掺杂含量的增加呈线性下降趋势.DSC结果显示Bi₄Ti_3-xNb_xO_12+x/2材料在居里温度处经历了一级铁电相变.样品的铁电性能测试结果表明, Nb⁵⁺掺杂Bi₄Ti₃O₁₂提高了材料的剩余极化Pr,这主要是由于^_Nb5+取代Ti⁴⁺大大降低了材料中氧空位的浓度,使得氧空位对畴的钉扎作用减弱的缘故.     

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.     

Dielectric and ferroelectric properties of Bi(Zn1/2Ti1/2)O3-PbTiO3-PbZrO3 ternary ceramics

Ceramics of a new ternary solid solution system, xBi(Zn(1/2)Ti(1/2))O(3-yPbTiO(3)z)PbZrO(3) (xBZT-yPT-zPZ), with compositions along the solubility limit curve are prepared by solid-state reaction and sintering technique. Two morphotropic phase boundaries (MPBs) separating the orthorhombic and tetragonal (MPB(O-T)) phases and the tetragonal and rhombohedral (MPB(T-R)) phases, respectively, are observed with increasing z (0.10 ≤ x ≤ 0.21; 0 ≤ y ≤ 0.49). It is found that the transition from the ferroelectric to paraelectric phase becomes more diffuse with the addition of BZT into the PZT solid solution. Enhanced dielectric and ferroelectric properties appear at MPB(R-T), which exists over a wide composition region (0.45 ≤ z ≤ 0.6), as revealed by X-ray diffraction and dielectric measurements. The dielectric constant reaches a maximum value (ε' = 1250) on the tetragonal majority side of the MPB. The highest remnant polarization (P(r) = 34.2 μC/cm(2)) is found in the composition at the center of the MPB, where the rhombohedral and tetragonal phases coexist in almost equal quantities.