Na0.5Bi0.5TiO3-BaTiO3陶瓷的介电和压电性能研究

研究了Ｎａ_０．５Ｂｉ_０．５ＴｉＯ_３和（Ｎａ_０．５Ｂｉ_０．５）_０．９４Ｂａ_０．０６ＴｉＯ_３陶瓷的电滞回线、压电性能和热滞现象·得到（Ｎａ_０．５Ｂｉ_０．５）_０．９４Ｂａ_０．０６ＴｉＯ_３陶瓷的剩余极化Ｐ_ｒ＝１９ｕＣ／ｃｍ^２、矫顽场Ｅ_ｃ＝４．７ｋＶ／ｍｍ．发现用适量的Ｂａ^２＋取代（Ｎａ_０．５Ｂｉ_０．５）^２＋尽管压电性能有所提高,但同时使得材料的温度稳定性大大降低．     

LiNiO2热分解反应动力学研究

用ＤＴＡ和ＸＲＤ研究了ＬｉＮｉＯ_２在空气中的热分解过程为：ＬｉＮｉＯ_２（ｓ）→(６５０～７２０℃)Ｌｉ_２Ｎｉ_８Ｏ_{１０（ｓ）}＋４Ｌｉ_２Ｏ_（ｓ）＋Ｏ_２（ｇ）→(８５０～９５０℃)Ｌｉ_２Ｏ_（ｓ）＋８ＮｉＯ_（ｓ）＋１／２Ｏ_２（ｇ） →(１０００～１１５０℃)ＮｉＯ（ｓ）＋Ｌｉ_２Ｏ_（ｇ）用 Ｄｏｙｌｅ－Ｏｚａｗａ法和 Ｋｉｓｓｉｎｇｅｒ法计算了各反应阶段的表观活化能分别为 ７４７．１８±１．０ ｋＪ·ｍｏｌ^－１、９３２．４６±１．０ ｋＪ·ｍｏｌ^－１和 １１２６．９７±１．０ ｋＪ·ｍｏｌ^－１．用 Ｋｉｓｓｉｎｇｅｒ法确定了反应级数和频率因子,确定了三个阶段的动力学方程分别为 ｄα／ｄt＝１．７３６ｘ１０３９ｅ^{－９００００／Ｔ}（１－α）^{１．０５７}; ｄα／ｄｔ＝１８０６×１０^３９ｅ^{－１１１５００／Ｔ}（１－α）^{０．８４４};ｄα／ｄｔ＝４．２６２×１０４２ｅ^{－１３５０００／Ｔ}（１－α）^{１．２７５}     

铋掺杂铌镁酸铅陶瓷的制备及其有序现象研究

采用二步固相合成法制备钙钛矿相的掺铋铌镁酸铅陶瓷,利用ＸＲＤ和ＴＥＭ选区电子衍射技术对Ｂ位离子非计量有序排列结构进行了表征．研究表明,当为施主掺杂而提高Ｍｇ^２＋、Ｎｂ^５＋离子比例时,铌酸镁前驱体中逐渐出现六方Ｍｇ_４Ｎｂ_９Ｏ_６相．施主Ｂｉ^３＋离子能够有效促进有序微区长大,提高系统有序度．利用Ｘ射线衍射线宽法对ＸＲＤ慢扫描谱进行处理,求得当掺入５％Ｂｉ^３＋离子时,有序微区平均尺寸由纯ＰＭＮ的５nｍ提高到２２ｎｍ．     

共沉淀法制备掺杂氧化锌压敏陶瓷粉料热力学分析

本文通过对Ｍｅ^ｎ＋（Ｚｎ^２＋;Ｃｒ_３^＋,Ｍｎ^２＋;Ｓｂ^３＋,Ｂｉ^３＋,Ｃｏ^２＋）－ＮＨ_３－ＣＯ_３^２－－Ｈ_２Ｏ体系进行热力学分析的基础上,获得了Ｍｅ－ＮＨ_３－ＣＯ_３^２－Ｈ_２Ｏ体系中的ｌｇ［Ｍ］_T－ｐＨ关系图,得到了用ＮＨ_４ＨＣＯ_３和ＮＨ_３·Ｈ_２Ｏ作沉淀剂,用共沉淀法制备掺杂氧化锌压敏陶瓷粉料时,最佳共沉淀ｐＨ为７．０左右．     

高Tc铋层状压电陶瓷结构与性能

综述了铋层状压电陶瓷的结构特点及性能研究,铋层状压电陶瓷的（Ｂｉ２Ｏ２）＾２＋层和钙钛矿层（Ａｍ－１ＢｍＯ３ｍ＋１）＾２－按一定规则 排列而成,上Ａ为适合于１２配位的离子;Ｂ为适合于八面体配位的离子,ｍ为一整数,其值一般为１￣５,与钛酸钡（ＢａＴｉＯ３）或锆钛酸铅（ＰＺＴ）陶瓷相比,铋层状压电陶瓷具有以下特点：低介电常数、高ＴＣ、机电耦合系数各向异性明显、低老化率、高电阻率等。     

Li2MnO3的柠檬酸盐溶胶-凝胶法合成及离子导电性

以Ｌｉ_２ＣＯ_３、ＭｎＣＯ_３为原料,用柠檬酸盐溶胶凝胶法合成了Ｌｉ_２ＭｎＯ_３超微粉．对合成的材料进行了ＤＴＡ、ＴＧ、ＸＲＤ和ＴＥＭ等表征,并应用交流阻抗谱技术测定了样品的电导率．结果表明,６５０。Ｃ以上生成Ｌｉ_２ＭｎＯ_３纯相超微粉,粒径在５０nｍ以下．在１８～４００℃温度范围内,产物烧结体的离子导电率为１０^－６～１０^－３Ｓ·ｃｍ^－１,其电导活化能为４４．８７ｋＪ·ｍｏｌ^－１．     

CoxR1-xAl2O4(R=Zn,Mg)钴蓝颜料反射性能的研究

采用化学共沉淀法成功地制备出适用于彩电显象管内荧光体着色的Ｃｏ_ｘＲ_１－ｘＡｌ_２Ｏ_４（Ｒ＝Ｚｎ、 Ｍｇ, ｘ＝０．８～１．０）钴蓝颜料： ４５０ｎｍ波长处反射率最大提高１８．２％, ６００ｎｍ处反射率最大降低５％。通过对该颜料反射率的影响因素,如掺杂离子类型、掺杂浓度和Ｃｏ^２＋离子浓度的探讨,结论如下：Ｚｎ^２＋、Ｍｇ^２＋改变钴蓝颜料反射性能的作用机理为晶格畸变引起Ｃｏ^２＋３ｄ轨道电子能级分裂程度的变化;对于掺杂离子Ｚｎ^２＋、Ｍｇ^２＋,ｘ下限值分别约为０．８５和０．８．     

疏水型SiO2气凝胶

以多聚硅为硅源,通过溶胶-凝胶、表面修饰及超临界干燥过程制备出了疏水型ＳｉＯ_２气凝胶．表面修饰后ＳｉＯ_２气凝胶孔洞由修饰前的２３．１ｎｍ减小到１８．２ｎｍ;比表面积由修饰前的 ４７７ｍ２ｇ^－１增加到 ５６３ｍ２ｇ^－１,骨架颗粒比修饰前略大,饱和水蒸汽吸附量由吸附前的０．０４（重量比）降低到０．００１２,且与水不浸润．     

铬掺杂对PZT-PMN陶瓷材料性能的影响

采用ＴＥＭ、ＳＥＭ、ＥＳＲ（电子自旋共振）结合常规压电性能测试手段研究了Ｃｒ_２Ｏ_３掺杂对ＰＺＴ－ＰＭＮ陶瓷的压电性能、微结构及畴态的影响．压电性能测试结果表明,当Ｃｒ_２Ｏ_３含量低于０．０６Ｗｔ％时,可使Ｋ_ｐ和Ｑ_ｍ同时提高,这说明铬掺杂同时兼具“软掺杂”与“硬掺杂”的双重特性．此外,还发现随着烧结温度的提高,材料性能“硬化”明显．ＥＳＲ谱分析表明,Ｃｒ离子主要以Ｃｒ^３＋和 Ｃｒ^５＋的方式共存,随着烧结温度的提高,它有从高价态 Ｃｒ^５＋或Ｃｒ^６＋向低价态转变的趋势,这一价态变化被认为是材料性能随烧结温度提高而“变硬”的主要原因之一．ＴＥＭ图片显示,随着掺杂的Ｃｒ_２Ｏ_３的浓度的增大,由于氧空位或受主离子与氧空位构成的缺陷复合体对畴壁的钉扎,电畴将从正规带状畴向波纹状畴转变．     

纳米相铁红粒子的液相制备

由０．２ｍｏｌ·Ｌ^－１Ｆｅ^３＋采用微波诱导加热制备了纳米尺寸的准立方形和纺锤形α－Ｆｅ_２Ｏ_３粒子,与常规加热方式比较微波加热制得的α－Ｆｅ_２Ｏ_３粒子粒径小且分布均匀,实验证明无机离子加 Ｈ^＋、ＯＨ^－和 Ｎａ^＋等的加入可明显加速反应速率．     

Ferroelectric, dielectric and piezoelectric properties of potassium lanthanum bismuth titanate K0.5La0.5Bi4Ti4O15 ceramics

The Aurivillius type bismuth layer-structured compound potassium lanthanum bismuth titanate (K_0.5La_0.5Bi₄Ti₄O₁₅) is synthesized using conventional solid-state processing. The phase analysis is performed by X-ray diffraction (XRD) and the microstructural morphology is conducted by scanning electron microscopy (SEM). The ferroelectric, dielectric and piezoelectric properties of K_0.5La_0.5Bi₄Ti₄O₁₅ (KLBT) ceramics are investigated in detail. The remnant polarization (P_r) and coercive field (E_c) are found to be 8.6 μC cm⁻² and 60 kV cm⁻¹, respectively. The Curie temperature T_c and piezoelectric coefficient d₃₃ are 413 °C and 18 pC N⁻¹, respectively.     

含铋层状结构陶瓷CaBi2Nb2O9的A位掺杂改性研究

利用固相反应法合成了Ca1-x(KLa)x/2Bi2Nb2O9(x=0～0.20)(xKLaCBNO)铋层状陶瓷,分析不同KLa掺杂量对CaBi2Nb2O9(CBNO)基陶瓷微观结构、介电、压电及电导性能的影响.XRD分析表明KLa的引入未改变CBNO陶瓷的单相结构.SEM和介电系数温度谱结果分别显示,KLa掺杂量的增加,细化尺寸趋于一致,而居里温度(Tc)从943℃降低至875℃,其峰值介电常数减小、峰值介电损耗增大.当掺杂量x=0.1时,样品的高温电阻率较纯CBNO显著升高,压电系数d33由5.2 pC/N提高到15.8 pC/N,居里温度高达870℃,说明A位(KLa)掺杂改性后的CBNO陶瓷在高温传感器等领域具有潜在的应用前景.     

SrCaBi_4Ti_5O_(18)-BiMeO+3(Me=Ga,Mn)高温无铅压电陶瓷的制备及性能

采用固相合成法制备了(1-x)SrCaBi_4Ti_5O_(18-x)BiMeO_3(SCBT-xBMe,Me=Ga,Mn;0≤x≤0.02)铋层状压电陶瓷,研究了BiMeO_3掺杂对SrCaBi_4Ti_5O_(18)系陶瓷微观结构及电性能的影响。结果表明BiMeO_3掺杂并未改变SCBT陶瓷的晶体结构,所有样品均为单一的铋层状结构陶瓷;适量引入BiMeO_3能促使SCBT的晶粒长大且趋于均匀,并有助于SCBT电性能的优化。当BiMeO_3掺杂量为0.005(Me=Ga)和0.02(Me=Mn)时,材料的压电常数d33分别为18pC/N和20pC/N,同时材料具有高的居里温度(Tc=550℃)和低的介电损耗(tanδ0.15%)。此外,SCBTxBMe材料具有良好的压电稳定性,适合于制备高温高频压电器件。     

Piezoelectric properties and thermal stabilities of cobalt-modified potassium bismuth titanate

The cobalt-modified potassium bismuth titanate (K_0.5Bi_4.5Ti₄O₁₅, KBT) piezoelectric ceramics have been prepared using conventional solid–state reaction. X-ray diffraction analysis revealed that the cobalt-modified KBT ceramics have a pure four-layer (m = 4) Aurivillius-type structure. The dielectric, ferroelectric, and piezoelectric properties of cobalt-modified KBT ceramics were investigated in detail. The piezoelectric activities of KBT ceramics were significantly improved by the cobalt modification. The reasons for piezoelectric activities enhancement with cobalt modification were given. The piezoelectric coefficient d₃₃ and Curie temperature T_c for the 5 mol% cobalt-modified KBT ceramics (KBT-Co5) were found to be 28 pC/N and 575 °C, respectively. The DC resistivity, frequency constants (N_p and N_t), and electromechanical properties at elevated temperature were investigated, indicating the cobalt-modified KBT piezoelectric ceramics possess stable piezoelectric properties up to 500 °C. The results show the cobalt-modified KBT ceramics are potential materials for high temperature piezoelectric applications.     

Enhanced electrical properties of textured NBBT ceramics derived from the screen printing technique

(001)(pc)-oriented (Na(0.5)Bi(0.5))(0.94)Ba(0.06)TiO(3) (NBBT) lead-free piezoelectric ceramics were fabricated by the screen printing technique using Na(0.5)Bi(0.5)TiO(3) (NBT) templates. The plate-like NBT template particles were synthesized from bismuth layer-structured ferroelectric Bi(4)Ti(3)O(12) (BiT) precursors by the topochemical method. The screen printed NBBT ceramics with 20 wt% NBT templates contained a large fraction of grains aligned with their c-axis normal to the sample surface, giving a Lotgering factor of 0.486. The dielectric and ferroelectric properties of textured NBBT ceramics were anisotropic. Compared with the non-textured NBBT ceramics, the dielectric, ferroelectric, and piezoelectric properties of the textured NBBT ceramics were improved, giving a dielectric constant ?(T)(33)/?(0) of 910, a remnant polarization P(r) of 29.2 μC/cm(2), a coercive field E(c) of 23.5 kV/cm, a piezoelectric coefficient d(33) of 180 pC/N, and a thickness-mode electromechanical coupling coefficient k(t) of 0.485.     

Giant electromechanical response in layered ferroelectrics enabled by asymmetric ferroelastic switching

Bismuth layer-structured ferroelectrics (BLSFs) are highly desired for high-temperature piezoelectric systems owing to their high Curie temperature and large spontaneous polarization. However, the inferior electromechanical response, which results from their unique layered crystal structure and inherently low piezoelectric activities, has restricted the practical application. Here, we report discovery of a large electric-field-induced strain in a simplest BLSF Bi₂WO₆, which is comparable to perovskite ferroelectrics and exhibits an intriguing asymmetric loop-like feature. Through comprehensive analysis on the displacement test configuration and polarization switching process, it is demonstrated that the exotic loop-like strain curve originates from the reversible bending deformation induced by asymmetric 90° ferroelastic switching in the upper and lower surfaces. Specifically, the textured Bi₂WO₆ ceramic exhibits a giant nominal strain value of ∼0.75% with excellent cycling stability. This discovery raises the possibility of utilizing the bending effect and ferroelastic switching to design piezoelectric actuators and may accelerate the development of high-performance lead-free ceramics.     

Sm掺杂增强PZT基弛豫型铁电陶瓷压电性能研究

锆钛酸铅(PZT)基压电陶瓷是一类应用非常广泛的功能材料,可应用于水声换能器、压电马达、医疗超声换能器以及声表面波滤波器等。通过改性提高PZT基压电陶瓷的压电性能一直是该领域的研究热点。本工作采用传统固相反应法制备了准同型相界(Morphotropic Phase Boundary, MPB)组分的Sm-0.25PMN-0.75PZT压电陶瓷,并对其微观结构以及宏观性能进行了系统研究。研究结果表明:引入Sm³⁺可以增强压电陶瓷的局域结构异质性,提升介电响应从而提高压电性能。当Sm³⁺引入过多时,铁电极化的长程连续性被大面积打断,压电性能下降。本实验中得到的最优组分压电陶瓷性能为:高压电系数d₃₃～824 pC/N,高压电电压常数g₃₃～27.1×10^–3m²/C和相对较高居里温度T_C～178℃,电致应变在室温至150℃范围内低于5%,有较好的温度稳定性,是极具应用前景的高性能压电材料。     

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.     

The effects of CuO-doping on dielectric and piezoelectric properties of Bi<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>TiO<Subscript>3</Subscript>–Ba(Zr,Ti)O<Subscript>3</Subscript> lead-free ceramics

CuO-doped lead-free ceramics based on bismuth sodium titanate (Bi_0.5Na_0.5TiO₃, BNT) and barium zirconate titanate (Ba(Zr_0.07Ti_0.93)O₃, BZT) were prepared via a multi-step solid-state reaction process. The BNT–BZT with CuO dopant ceramics sintered at 1150–1180 °C for 2 h in air showed a pure perovskite structure. SEM images reveal that a small amount of CuO (<2 mol%) play a significant role on the microstructure to improve its sintering attributes, while it will degrade when the dopant is added beyond 2 mol%. The dielectric and piezoelectric properties of CuO-doped BNT–BZT ceramics were evaluated. At room temperature, the sample doped with 2 mol% CuO shows quite good properties such as a high piezoelectric constant (d ₃₃ ∼156.5 pC/N) and a high electromechanical coupling factor (k _t ∼52%). The depolarization temperature increased dramatically and the maximum permittivity temperature decreased slightly.     

Ferroelectric and piezoelectric properties of (1 − x) (Bi0.5Na0.5)TiO3–xBaTiO3 ceramics

Lead-free ceramics based on bismuth sodium titanate (Bi_0.5Na_0.5TiO₃, BNT)–barium titanate (BaTiO₃,BT) have been prepared by solid state reaction process. The (1?x)BNT–(x)BT (x = 0.01,0.03,0.05,0.07) ceramics were sintered at 1,150 °C for 4 h in air, show a pure perovskite structure. X-ray diffraction analysis indicates that a solid solution is formed in (1?x)BNT–(x)BT ceramics with presence of a morphotropic phase boundary (MPB) between rhombohedral and tetragonal at x = 0.07. Raman spectroscopy shows the splitting of (TO₃) mode at x = 0.07 confirming the presence of MPB region. The temperature dependence dielectric study shows a diffuse phase transition with gradual decrease in phase transition temperature (T_m). The dielectric constant and diffusivity increases with increase in BT content and is maximum at the MPB region. With the increase in BT content the maximum breakdown field increases, accordingly the coercive field (E_c) and remnant polarization (P_r) increases. The piezoelectric constant of (1 ? x)BNT–(x)BT ceramics increases with increase in BT content and maximum at x = 0.07, which is the MPB region. The BNT–BT system is expected to be a new and promising candidate for lead-free dielectric and piezoelectric material.