含铋层状结构陶瓷CaBi2Nb2O9的A位掺杂改性研究

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宗立超, 曾江涛, 赵苏串, 阮伟, 李国荣. 含铋层状结构陶瓷CaBi₂Nb₂O₉的A位掺杂改性研究 . 无机材料学报, 2012, 27(7): 726-730
ZONG Li-Chao, ZENG Jiang-Tao, ZHAO Su-Chuan, RUAN Wei, LI Guo-Rong. Study on A-site Cation Doping of CaBi₂Nb₂O₉ with Bismuth Layered Structure . Journal of Inorganic Materials, 2012, 27(7): 726-730 复制到剪切板

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含铋层状结构陶瓷CaBi₂Nb₂O₉的A位掺杂改性研究

宗立超^1,², 曾江涛², 赵苏串¹, 阮伟², 李国荣²

1. 上海大学物理系, 上海 200444

2. 中国科学院上海硅酸盐研究所, 上海 200050

宗立超(1986-), 男, 硕士研究生. 通讯作者: 李国荣, 研究员. E-mail:grli@sunm.shcnc.ac.cn

基金:国家自然科学基金(51011120098, 50977088); 国家自然科学基金委员会与中国工程物理研究院联合基金(10876041);

摘要

利用固相反应法合成了Ca_1-_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(T_c)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.

关键词: 压电陶瓷; 掺杂; 压电系数; CaBi₂Nb₂O₉

中图分类号:O469 文献标志码:A 文章编号:1000-324X(2012)07-0726-05

Study on A-site Cation Doping of CaBi₂Nb₂O₉ with Bismuth Layered Structure

ZONG Li-Chao^1,², ZENG Jiang-Tao², ZHAO Su-Chuan¹, RUAN Wei², LI Guo-Rong²

1. Shanghai University, Physic Department, Shanghai 200444, China

2. Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China

Fund:National Nature Science Foundation of China (51011120098, 50977088); NSAF (10876041);

Abstract

High curie temperature piezoelectric ceramics based on KLa-doped Ca_1-_x(KLa)_x_/2Bi₂Nb₂O₉(x=0-0.20) were prepared by a conventional solid state reaction method. Crystal structure and microstructures of Ca_1-_x(KLa)_x_/2Bi₂Nb₂O₉ ceramics were characterized by XRD and SEM. XRD patterns show that the crystal structures are a single phase of bismuth oxide layer structure having general formula (Bi₂O₂)²⁺(A_m_-1B_mO₃_m₊₁)^2-withm = 2. The grains of polished and thermally etched surfaces revealled a plate-liked morphology. The Curie point (T_c) decreases obviously whereas the piezoelectric activity of CBNO ceramics is significantly improved by the doping of potassium and lanthanum. The KLa-doped CBNO materials have an electrical conductivity value 1-2 orders of magnitude lower than undoped samples. The thermal depoling behavior of Ca_1-_x(KLa)_x_/2Bi₂Nb₂O₉ceramics shows that all of them have a high Curie point (T_c≥850℃) and show good resistance to thermal depoling up to temperatures close to their Curie points. The results showed that the excellent properties is obtained in the ceramics with composition ofx=0.1,i.e.d₃₃=15.8 pC/N,T_c=870℃ and the DC conductivity is one order of magnitude smaller than that of undoped CBNO. All the results suggest that the doped CaBi₂Nb₂O₉ is a potential material for high temperature sensor.

Keyword: piezoelectric ceramics; modified; d₃₃; CaBi2Nb2O9

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随着现代科学技术的高速发展, 能源、汽车、航空航天、石油化工、地质勘探、原子能等众多工业部门和科研机构急需能够在更高温度下工作的电子设备^{[ 1]}. 传统PZT系列压电陶瓷由于其优异的压电性能在驱动器、传感器等领域得到了广泛生产应用, 但其居里温度低, 限制了PZT系列陶瓷的使用温度区域^{[ 2]}. 目前高温压电材料主要是LiNbO₃压电单晶材料和含铋层状压电陶瓷. LiNbO₃单晶由于其高居里温度和优良的压电性能, 已经成为高居里温度压电材料的重要组成部分, 但是, 压电单晶材料生产工艺复杂、成本高、机械性能差, 不便于在高压环境下使用^{[ 3]}; 含铋层状结构压电陶瓷因具备高 T _c、低介电常数、机电耦合系数各向异性明显、低老化率、高电阻率、生产成本低廉且易于改性等优点, 在高温压电领域有着广阔的应用前景^{[ 4]}.

CaBi₂Nb₂O₉(CBNO)是一种典型的含铋层状结构压电材料, 它是由类钙钛矿层(CaNb₂O₇)^2-和(Bi₂O₂)²⁺层有规律的交替排列而成, 居里温度极高, 达到了943℃, 然而它的压电性能较低, d₃₃仅为7 pC/N^{[ 5]}. 这是由于铋层状材料的自发极化主要位于 a- b平面, 其自发极化转向受到二维平面限制, 很难通过极化得到较高的压电性能. 为了解决这一问题, 国内外科研工作者改进了制备工艺, 并对其进行掺杂改性, 取得了一些重要进展, 如晏海学等^{[ 5]}采用放电等离子烧结法制备的CBNO陶瓷, 在 a-b平面内压电性能高达19 pC/N, 但是该工艺方法得到的CBNO陶瓷的电导率过大, 难以极化, 而且在高温下的漏电流比随机取向的陶瓷大, 给高温下的应用造成困难. 张晓东等^{[ 6]}采用A位取代对其进行改性, 特别研究了改性后材料的高温性能, 改性后CBNO陶瓷的压电性明显改进( d₃₃最高为13 pC/N), 但高温电阻率及居里温度均有所下降.

一般而言, 在含铋层状结构化合物中, A位取代改性的效果要比B位取代改性的效果更加明显, 这是因为B位离子半径一般相差不大, 更容易进入晶格, 随着取代量的增加, 晶格常数变化幅度远远小于A位取代^{[ 4]}. 王春明等^{[ 7]}对CBNO陶瓷进行A位取代时, 压电性能得到明显改善, 但因为Ca²⁺的有效半径小于取代离子La³⁺, T_c下降明显. 晏海学等^{[ 8]}对m=4的CaBi₄Ti₄O₁₅陶瓷进行了A位(NaCe)复合离子掺杂取代, 改性后材料的压电活性和高温电阻率均有所提升. 本工作选用(KLa)复合离子对CBNO进行A位取代改性, 研究了不同(KLa)含量的取代对CBNO陶瓷的结构和性能的影响.

1 实验

采用传统的固相反应法分别制备了Ca_1- _x(KLa) _x_/2Bi₂Nb₂O₉( x=0、0.05、0.10、0.15、0.20)( xKLaCBNO)陶瓷. 以分析纯的Bi₂O₃、CaCO₃、Nb₂O₅、La₂O₃和K₂CO₃为原料, 将所有原料按相应的化学计量比称量, 球磨混合6 h, 在850℃预烧3 h获得具有CBNO正交相结构的单相化合物, 合成好的粉料粉碎后二次球磨6 h, 压成φ12 mm×1.0 mm的圆片, 接着800℃排塑1 h, 最后在1100~1200℃烧结3 h. 将所有陶瓷样品双面磨平至0.5 mm, 涂Pt电极, 并在1000℃保温20 min, 以备性能测试. 将样品放入100℃的硅油中极化10~15 min, 极化电压为15~20 kV/mm, 放置24 h后进行性能测试.

采用阿基米德法测量材料密度. 用日本岛津(RAX-10)X射线衍射(XRD)仪进行物相分析. 用扫描电镜(SEM)(HITACHI S-570)和原子力显微镜(AFM)(SPA 400, SPI3800N)观察样品的晶粒形貌. HP4294阻抗分析仪和ZJ-3A型准静态 d ₃₃测量仪分别用来测量样品的介电和压电性能. 样品的直流电阻率采用高阻仪(KEITHLEY 6517A)测量.

2 结果和讨论

2.1 微结构分析

图1所示为Ca_1- _x(KLa) _x_/2Bi₂Nb₂O₉( x=0~0.2)陶瓷样品的XRD图谱. 从图1发现所有样品均为双层铋层状结构铁电体, 没有检测到第二相, 可见在掺杂范围内, KLa掺杂并不影响材料的晶体结构. 在XRD图谱中相对强度最高的峰为(115)衍射峰, 这与铋层结构化合物XRD最强的衍射峰为(112 m+1)是相符合的^{[ 8]}.

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	图1 xKLaCBNO陶瓷样品的XRD图谱Fig. 1 XRD patterns of xKLaCBNO ( x=0, 0.05, 0.10, 0.15, 0.20) ceramics

图2为精修的晶格常数 a、 b、 c随(KLa)掺杂含量的变化关系. 当掺杂含量为 x=0.05时, a、 b、 c均减小, 但随着(KLa)掺杂量的增大, a、 b、 c均逐渐增大. 这与(KLa)在晶格中的取代位置有关. Armstrong和Newnham曾提出含铋层状结构中钙钛矿适于12配位的位置可以被取代, 而(Bi₂O₂)²⁺层中的Bi不易被取代^{[ 9]}, 这点被Osada等^{[ 10]}通过拉曼光谱研究所证实. K⁺和La³⁺将分别取代类钙钛矿层中A位Ca²⁺导致晶格中产生空位, 晶格产生畸变. 在这种情况下, 电畴运动比较容易进行, 在相当小的电场或者机械应力作用下, 就能使畴壁运动, 极化处理时有利于自发极化转向, 从而明显提高压电性能.

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	图2 不同掺杂量 x对 xKLa CBNO陶瓷晶格常数的影响Fig. 2 Lattice parameter of the xKLaCBNO ceramics as functions of x

图3为CBNO和0.1KLaCBNO陶瓷的自然断面与抛光热腐蚀后的扫描电镜照片. CBNO陶瓷样品的表面呈现为随机排列的棒状结构, 沿断面晶粒呈片状生长, 这是铋层状结构材料的一个显著特征. 由于铋层状化合物微观晶体结构的各向异性^{[ 11]}, 导致了晶粒沿着晶胞单元的 a-b平面的生长速度远大于沿着 c轴方向的生长速度. 也即如图中所示, 晶粒沿直径方向的尺寸远大于沿高度方向的尺寸, 从断面图中观察到沿着 a-b平面的方向长成片状, 从侧面观察到如图(a)中所示的棒状晶粒. 当掺杂量 x =0时圆盘状晶粒的厚度远远小于它的长度. 这是因为铋层状结构化合物沿着垂直于 c轴方向晶粒增长速率快的缘故, 导致晶粒结构明显各向异性. 当 x =0.10时, 晶粒取向趋近于一致, 部分晶粒发育不完全, 晶粒尺寸变小, 且尺寸分布变宽, 产生了许多细小晶粒, 可能是由于La的掺杂抑制了晶粒的长大, 这与顾大国等^{[ 12]}在La对CaBi₄Ti₄O₁₅掺杂改性时的发现是一致的.

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	图3 CBNO(a,b)和0.1KLaCBNO(c,d)陶瓷的自然断面与抛光热腐蚀后的SEM照片Fig. 3 SEM images for nature section and polished and thermally etched surfaces of CBNO(a,b) and 0.1KLaCBNO (c,d)

2.2 介电和压电性能

表1为室温下纯CBNO和(KLa)掺杂后CBNO陶瓷的物理性能参数. 从表1中可以看出, 在相同的工艺条件下, 掺杂后样品的相对密度( ρ_rd)高于纯CBNO, KLa掺杂取代使烧结后的样品变得更加致密. 掺杂后样品在100 kHz下的介电常数( ε_r)和介电损耗(tan δ)均有所增加. 当掺杂量 x=0.1时, 样品的压电常数 d₃₃由5.2 pC/N增加到15.8 pC/N, 掺杂后样品的压电性能得到了极大的提升, 这可能是因为La³⁺取代了A位的Ca²⁺, 产生电子, 抵消空穴, 提高了样品的高温电阻率, 进而可以使陶瓷可以在高电场下进行有效极化.

表1 纯CBNO和 xKLaCBNO陶瓷室温介电压电性能(100 kHz) Table 1 Properties of CBNO and xKLaCBNO at room temperature (100 kHz)

图4为纯CBNO和0.1KLaCBNO的相对介电常数和介电损耗的温度曲线(100 kHz). 从图中可以看出, 随着KLa掺杂取代量的增加, 材料的居里温度由943℃降低至875℃. 这主要是由于K⁺(0.164 nm)和La³⁺(0.136 nm)的离子半径均比Ca²⁺(0.134 nm)的半径大. 对于铋层状结构陶瓷材料来说, 其介电常数和介电损耗的温度依赖性和频率依赖性很弱, 在远离相变温度区几乎不随温度发生变化, 随频率的变化也很不明显. Subbarao等^{[ 13]}曾指出, 居里温度的高低与取代离子的半径和电负性有关, 随取代离子半径增大而降低, 随取代离子电负性升高而增加, 在铋层状结构化合物中, 类钙钛矿层中A位离子半径越大其居里温度越低, A位阳离子半径的增大(偏离类钙钛矿亚结构)导致晶格变形, 相应的沿着极化轴( ab轴)原子的位移变小, 因此达到高温结构的能量减少^{[ 14, 15]}.

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	图4 纯CBNO和0.1KLaCBNO的相对介电常数和介电损耗的温度曲线(100 kHz)Fig. 4 Temperature dependence of dielectric permittivity and loss tan δ for xKLaCBNO ceramics (100 kHz)

从损耗曲线可以看出, 纯CBNO和掺杂KLa的CBNO陶瓷都具有很低的介电损耗. 在500~750℃时, 0.1KLaCBNO的介电损耗比纯CBNO陶瓷介电损耗低. 当温度继续升高, 掺杂后的介电损耗又比未掺杂的介电损耗高, 尤其是当温度越过居里温度时, 介电损耗急剧增加.

综合来说, 当取代量 x=0.1时, 材料具有最佳介电温度稳定性, 仍具极高居里温度, 使其可能在高温中应用.

为了考察(KLa)掺杂取代后材料的高温稳定性, 将Ca_1- _x(KLa) _x_/2Bi₂Nb₂O₉( x=0~0.20)在不同温度下去极化2 h后, 测量在室温下压电系数, 结果如图5所示. 从图5中可以看出, 当取代量 x=0.1时, 样品的压电系数得到极大提升; 并在850℃以下, 压电活性的温度稳定性良好, 这也使改进后的陶瓷材料可能在高温中应用.

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	图5 xKLaCBNO陶瓷样品的压电常数与去极化温度之间的关系Fig. 5 Effect of annealing temperature (for 2 h) on the d₃₃of xKLaCBNO ceramics

2.3 电导性能

图6是 xKLaCBNO陶瓷材料的直流电阻率随温度的变化曲线. 从图中可以看出适量KLa取代显著提高了样品的直流电阻率. 掺杂取代后的CBNO陶瓷材料具有更佳的电阻性能, 从而保证极化过程的顺利进行. CBNO是一种P型半导体^{[ 11]}, 这是因为Bi₂O₃的蒸汽压较高, 在高温下存在铋挥发, 在晶格中留下铋空位和氧空位, 在冷却过程中, 大气中氧气将会重新进入晶格内部, 并在价带产生空穴补偿不平衡电价. 在A位取代中, 当高价La³⁺离子取代Ca²⁺离子时, 起到一个正电中心的作用, 使得晶格中出现“多余”的电子, 每增加一个电子, 便可抵消一个空穴, 载流子浓度降低, 使得陶瓷的电导率降低, 即材料电阻率提高.

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	图6 xKLaCBNO陶瓷的电阻率随温度的变化曲线Fig. 6 Temperature dependence of resistivity of xKLaCBNO ceramics

无机材料在不同温区导电机制可分为三种: 低温时主要为杂质电导, 中温时为氧空位电导, 高温时本征电导. 为了进一步分析该材料的高温导电机理, 对陶瓷的直流电导率与温度关系进行Arrhenius拟合, 在高温段, 掺杂后的 xKLaCBNO陶瓷样品的电导激活能 E_a≥1.3 eV, 与某些铋层状以及钙钛矿铁电梯带隙(均源于TiO₆八面体带隙)的1/2接近^{[ 16, 17]}, 对应了材料的本征导电. KLa掺杂取代CBNO后的该电导激活能比纯CBNO增加了0.3 eV左右, 说明本征载流子激发跃迁受到的阻碍增加, 迁移率相应降低, 即(KLa)复合离子进入晶格后使材料的带隙增大.

3 结论

采用固相反应法制备了Ca_1- _x(KLa) _x_/2Bi₂Nb₂O₉( x=0~0.20)陶瓷. 研究结果显示所有样品都具有单一正交相结构, 掺杂后样品晶粒尺寸变小, 致密度略有提高; A位KLa掺杂取代显著降低了样品的居里温度, 改善了材料的压电性能, 提高了高温电阻率. 当掺杂量 x=0.1时, 0.1KLaCBNO陶瓷的 T_c＝870℃, d₃₃=15.8 pC/N, 上述研究结果表明适量A位(KLa)掺杂改性的CBNO在高温传感器等领域具有广阔的应用前景.

参考文献

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[1]	JIANG Xiang-Ping, YANG Qing, CHEN Chao, et al. Nb-modified Bi₄Ti₃O₁₂ piezoelectric for high temperature applications. Journal of Inorganic Materials, 2010, 25(11): 1169-1174. [本文引用:1] [JCR: 0.531] [CJCR: 1.106]
[2]	赁敦敏, 肖定全, 朱建国, 等. 从发明专利看无铅压电陶瓷的研究与发展——无铅压电陶瓷20年发明专利分析之一. 功能材料, 2003, 3(34): 312-315. [本文引用:1]
[3]	GU Da-Guo, LI Guo-Rong, ZHENG Liao-Ying, et al. Electrical properties of Mn-modified CaBi₄Ti₄O₁₅ piezoelectrics for high temperature application. Journal of Inorganic Materials, 2008, 23(3): 626-630. [本文引用:1] [JCR: 0.531] [CJCR: 1.106]
[4]	YAN Hai Xue, LI Cheng En, ZHOU Jia-Guang, et al. Structures and properties of bismuth layer-structured piezoelectric ceramics with high T_c. Journal of Inorganic Materials, 2000, 15(2): 209-220. [本文引用:2] [JCR: 0.531] [CJCR: 1.106]
[5]	Yan H X, Zhang H T, Ubic R, et al. A lead-free high-curie-point ferroelectric ceramic, CaBi₂Nb₂O₉. Adv. Mater. , 2006, 17(10): 1261-1265. [本文引用:2] [JCR: 14.829]
[6]	Zhang X D, Yan H X, Reece M J. Effect of A site substitution on the properties of CaBi₂Nb₂O₉ ferroelectric ceramics. J. Am. Ceram. Soc. , 2008, 91(9): 2928-2932. [本文引用:1] [JCR: 2.107]
[7]	Wang C M, Wang J F, Mao C L, et al. Enhanced dielectric and piezoelectric properties of aurivillius-type potassium bismuth titanate ceramics by cerium modification. J. Am. Ceram. Soc. , 2008, 91(9): 3094-3097. [本文引用:1] [JCR: 2.107]
[8]	Yan H X, Li C G, Zhou J G, et al. Effects of A-site (NaCe) substitution with Na-deficiency on structures and properties of CaBi₄Ti₄O₁₅-based high-curie-temperature ceramics. Jpn. J. Appl. Phys. , 2001, 40(11): 6501-6505. [本文引用:2] [JCR: 1.067]
[9]	Armstrong R A, Newnham R E. Bismuth titanate solid solutions. Mat. Res. Bull. , 1972, 7(10): 1025-1034. [本文引用:1]
[10]	Osada M, Kakihana M, Wada S, et al. Broken symmetry in low-temperature BaTiO₃ phases: strain effects probed by Raman scattering, Appl. Phys. Lett. , 1999, 75(21): 3393-3395. [本文引用:1] [JCR: 3.794]
[11]	Watcharapasorn A, Siriprapa P, Jiansirisomboon S. Grain growth behavior in bismuth titanate-based ceramics. J. Eur. Ceram. Soc. , 2010, 30(1): 87-93. [本文引用:2] [JCR: 2.36]
[12]	Santos V B, M’ Peko J C, Mir M, et al. Microstructural, structural and electrical properties of La³+-modified Bi₄Ti₃O₁₂ ferroelectric ceramics. J. Eur. Ceram. Soc. , 2009, 29(4): 751-756. [本文引用:1] [JCR: 2.36]
[13]	Subbarao E C. Grain size effects in advanced ceramics. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 1998, 133(1/2): 3-11. [本文引用:1] [JCR: 2.108]
[14]	Yan H X, Zhang Z, Zhu W M, et al. The effect of (Li, Ce) and (K, Ce) doping in Aurivillius phase material CaBi₄Ti₄O₁₅. Mat. Res. Bull. , 2004, 39(9): 1237-1246. [本文引用:1]
[15]	Hiroshi Irie, Masaru Miyayama, Tetsuichi Kudo. Electrical properties of a bismuth layer-structured Ba₂Bi₄Ti₅O₁₈ single crystal. J. Am. Ceram. Soc. , 2000, 83(11): 2699-2704. [本文引用:1] [JCR: 2.107]
[16]	Wang C M, Zhang S J, Wang J F, et al. Electromechanical properties of calcium bismuth niobate (CaBi₂Nb₂O₉) ceramics at elevated temperature. Mater. Chem. Phys. , 2009, 118(1): 21-24. [本文引用:1] [JCR: 2.072]
[17]	Jardiel T, Rubia M A, Peiteado M. Control of functional microstructure in WO₃-doped Bi₄Ti₃O₁₂ ceramics. J. Am. Ceram. Soc. , 2008, 91(4): 1083-1087. [本文引用:1] [JCR: 2.107]

2010

0.531

1.106

Journal of Inorganic Materials. 2010, 25(11):1169-1174 DOI:10.3724/SP.J.1077.2010.01169

Nb-modified Bi₄Ti₃O₁₂ piezoelectric for high temperature applications

(Department of Material Science and Engineering, Jingdezhen Ceramic Institute, Jingdezhen 333001, China)

Nb-modified Bi₄Ti₃O₁₂ (BIT+xmol%Nb₂O₅) layer-structured piezoelectric ceramics were prepared by the solid state reaction method (at the pressure of about 12MPa). The quantity of grain growth along a-b plane is much more than that along c-axis with the increasing amount of Nb₂O₅. After Nb₂O₅doping, the size of grain becomes small and unanimity. The electrical conductivity and dielectric loss are significantly reduced, while relative density, piezoelectric activity and electromechanical properties of Bi₄Ti₃O₁₂-based ceramics are improved by the modification of Nb₂O₅. The electrical conductivity of BIT+4.00mol% Nb₂O₅(10^-13S/cm) decreases by 2 orders of magnitude compared with the undoped one. Besides, the BIT+4.00mol% Nb2O5 ceramic exhibits optimum electrical properties: relative density r=98.7%, tanδ=0.23%, d₃₃=18pC/N, Q_m=2804, k_p=8.1%, k_t=18.6%, N_p=2227Hz·m and N_t=2025Hz·m, and the d₃₃ remains 17pC/N after annealing at 600℃, which indicates that the ceramic is a potential material for high temperature applications.

采用固相法(成型压力~12MPa)获得了Nb改性的Bi₄Ti₃O₁₂(BIT+xmol%Nb2O5)层状压电陶瓷. 研究发现随着Nb₂O₅含量的增加, a-b面取向的晶粒逐渐增多, 晶粒尺寸愈细化与均匀. Nb₂O₅的引入明显降低了BIT系列陶瓷的导电率和介电损耗, 提高了陶瓷的相对密度﹑压电与机电性能. 适量Nb₂O₅(x=4.00)掺杂时, 陶瓷的电导率(~10?13S/cm)比纯BIT的降低了2个数量级, 且该陶瓷的相对密度r=98.7%, tanδ=0.23%, d₃₃=18pC/N, Q_m=2804, k_p=8.1%, k_t=18.6%, N_p=2227Hz·m, N_t=2025Hz·m. BIT+xmol%Nb₂O₅(x=4.00)陶瓷在600℃经退极化处理后, 其d₃₃基本保持不变(~17pC/N), 表明该材料在高温器件领域具有良好的应用前景.

... 随着现代科学技术的高速发展, 能源、汽车、航空航天、石油化工、地质勘探、原子能等众多工业部门和科研机构急需能够在更高温度下工作的电子设备^[1] ...

2003

0.0

... 传统PZT系列压电陶瓷由于其优异的压电性能在驱动器、传感器等领域得到了广泛生产应用, 但其居里温度低, 限制了PZT系列陶瓷的使用温度区域^[2] ...

2008

0.531

1.106

Journal of Inorganic Materials. 2008, 23(3):626-630 DOI:10.3724/SP.J.1077.2008.00626

Electrical properties of Mn-modified CaBi₄Ti₄O₁₅ piezoelectrics for high temperature application

State Key Lab of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China

Mn-modified CaBi₄Ti₄O₁₅ (CBT+x mol% MnCO₃) layer-structured piezoelectric ceramics were prepared by the solid state reaction technology. All samples have the same Curie temperature of 780℃, but the dielectric loss at high temperature is remarkably lowered by Mn addition. With increasing content of Mn, the remnant polarization is slightly decreased; the dielectric constant at room temperature decreases from 173 to 162; and the mechanical quality factor increases from 2700 to 4400. The piezoelectric constant d₃₃ is enhanced from 7 to 14.5. The resistivity of 1.0mol% Mn modified sample is found to be 10⁸Ω·cm at 500℃, 50 times higher than that of pure CBT. The Arrehenius plot of Mn-modified CBT is fitted by 3 straight lines, while that of pure CBT is fitted by 2 straight lines. The results suggest that the Mn modified CBT is a potential material for high temperature sensing application.

采用固相法制备了Mn改性的CaBi₄Ti₄O₁₅(CBT+x mol% MnCO₃)层状压电陶瓷. 介电温谱显示所有样品居里点在780℃附近, 并且发现该材料在110K处有一介电弛豫峰. Mn的加入显著降低了高温下的介电损耗, 剩余极化轻微降低, 室温介电常数从173减小到162, 同时机械品质因子由2700增加到4400, 显示了硬性掺杂的效果. 在100~600℃范围内, x=1.0的样品比纯组分的电阻率提高了一个数量级以上, 500℃的电阻率提高了约2个数量级(10⁸Ω·cm), 电阻率对温度的Arrhenius拟合由两段过渡到三段, 压电系数d₃₃由7提高到14.5. 实验结果表明, Mn改性的CBT在高温传感器等领域具有应用前景.

... LiNbO₃单晶由于其高居里温度和优良的压电性能, 已经成为高居里温度压电材料的重要组成部分, 但是, 压电单晶材料生产工艺复杂、成本高、机械性能差, 不便于在高压环境下使用^[3] ...

2000

0.531

1.106

Journal of Inorganic Materials. 2000, 15(2):209-220

Structures and properties of bismuth layer-structured piezoelectric ceramics with high T_c

Shanghai Institute of Ceramics; Chinese Academy of Sciences; Shanghai 200050; China

This paper reviewed the structures and properties of bismuth layer-structured piezoelectric
ceramics. The structures of bismuth layer-structured piezoelectric ceramics are built up by the regular intergrowth of (Bi₂O₂)²⁺
layers and perovskite (A_m-1B_mO_3m+1)^2- slabs where A is a combination of cations adequate for 12-coordinated interstices,
B is a combination of cations well suited to octahedral coordinated, and m is an integer usually lying to the range 1-5. By comparison with
barium titanate (BaTiO_3) or lead zirconate titanate (PZT) ceramics, the bismuth layer-structured piezoelectric ceramics are characterized
by: (1) lower dielectric constant; (2) higher Curie temperature; (3) stronger anisotropy in electromechanical coupling factors; (4) lower
ageing rate; (5) higher resistivity; …etc..

Previous studies showed that Curie temperature depends on atomic displacement of polarization cations, spontaneous polarization, bismuth
content in the cubooctahedral cavities, and the nature of the substituting cations such as inonic radius, electronegativities and electronic
configuration. An essentially weak point of bismuth layer-structured piezoelectric ceramics is low piezoelectric activity which can be
solved by chemical substitution or fabrication methods for orientating the grains in ceramics. It is necessary to study the relationships
between structures and properties of bismuth layer-structured piezoelectric ceramics in order to develop the materials.

综述了铋层状压电陶瓷的结构特点及性能研究．铋层状压电陶瓷的结构由（Ｂｉ_２Ｏ_２）^２＋层和钙钛矿层（Ａ_ｍ－_１Ｂ_ｍＯ_３ｍ＋１）^２－按一定规则共生排列而成．此处Ａ为适合干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（ＢａＴｉＯ_３）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Ｔ_ｃ、机电耦合系数各向异性明显、低老化率、高电阻率等．先前研究证明，居里温度不仅与极化原子位移、自发极化强度、Ａ位Ｂｉ含量有关，而且还与取代离子的特性诸如离子半径、电负性、核外电子排布有关．压电活性低是铋层状陶瓷的本质缺点，通常发展该材料的途径为化学取代或晶粒取向技术．研究材料结构与性能之间的关系有助于发展铋层状压电陶瓷材料．

... 含铋层状结构压电陶瓷因具备高T_c、低介电常数、机电耦合系数各向异性明显、低老化率、高电阻率、生产成本低廉且易于改性等优点, 在高温压电领域有着广阔的应用前景^[4] ...

... 一般而言, 在含铋层状结构化合物中, A位取代改性的效果要比B位取代改性的效果更加明显, 这是因为B位离子半径一般相差不大, 更容易进入晶格, 随着取代量的增加, 晶格常数变化幅度远远小于A位取代^[4] ...

2006

14.829

0.0

... CaBi₂Nb₂O₉(CBNO)是一种典型的含铋层状结构压电材料, 它是由类钙钛矿层(CaNb₂O₇)^2-和(Bi₂O₂)²⁺层有规律的交替排列而成, 居里温度极高, 达到了943℃, 然而它的压电性能较低, d₃₃仅为7 pC/N^[5] ...

... 为了解决这一问题, 国内外科研工作者改进了制备工艺, 并对其进行掺杂改性, 取得了一些重要进展, 如晏海学等^[5]采用放电等离子烧结法制备的CBNO陶瓷, 在a-b平面内压电性能高达19 pC/N, 但是该工艺方法得到的CBNO陶瓷的电导率过大, 难以极化, 而且在高温下的漏电流比随机取向的陶瓷大, 给高温下的应用造成困难 ...

2008

2.107

0.0

... 张晓东等^[6]采用A位取代对其进行改性, 特别研究了改性后材料的高温性能, 改性后CBNO陶瓷的压电性明显改进(d₃₃最高为13 pC/N), 但高温电阻率及居里温度均有所下降 ...

2008

2.107

0.0

... 王春明等^[7]对CBNO陶瓷进行A位取代时, 压电性能得到明显改善, 但因为Ca²⁺的有效半径小于取代离子La³⁺, T_c下降明显 ...

2001

1.067

0.0

... 晏海学等^[8]对m=4的CaBi₄Ti₄O₁₅陶瓷进行了A位(NaCe)复合离子掺杂取代, 改性后材料的压电活性和高温电阻率均有所提升 ...

... 在XRD图谱中相对强度最高的峰为(115)衍射峰, 这与铋层结构化合物XRD最强的衍射峰为(112m+1)是相符合的^[8] ...

1972

0.0

... Armstrong和Newnham曾提出含铋层状结构中钙钛矿适于12配位的位置可以被取代, 而(Bi₂O₂)²⁺层中的Bi不易被取代^[9], 这点被Osada等^[10]通过拉曼光谱研究所证实 ...

1999

3.794

0.0

2010

2.36

0.0

J. Eur. Ceram. Soc.. 2010, 30(1):87-93 DOI:10.1016/j.jeurceramsoc.2009.07.031

Grain growth behavior in bismuth titanate-based ceramics

Abstract

Bismuth titanate and lanthanum-doped bismuth titanate ceramics were prepared from freeze-dried powders employing conventional solid state reaction and sintering procedures. The sintering process was carried out at 1150 °C from 4 up to 48 h. X-ray diffraction analysis showed that preferred orientation was reduced in bismuth titanate ceramic as sintering time increased while lanthanum-doped sample showed much less degree of preferred orientation and was independent of sintering time. Grain growth studies also showed that initial anisotropic grain growth rate was the main factor controlling the grain morphology, rendering the plate-shaped grain in both pure and lanthanum-doped bismuth titanate ceramics. Based on established grain growth law, pore-controlled diffusion could be the major mechanism determining the observed microstructure in these layered compounds.

... 由于铋层状化合物微观晶体结构的各向异性^[11], 导致了晶粒沿着晶胞单元的a-b平面的生长速度远大于沿着c轴方向的生长速度 ...

... CBNO是一种P型半导体^[11], 这是因为Bi₂O₃的蒸汽压较高, 在高温下存在铋挥发, 在晶格中留下铋空位和氧空位, 在冷却过程中, 大气中氧气将会重新进入晶格内部, 并在价带产生空穴补偿不平衡电价 ...

2009

2.36

0.0

J. Eur. Ceram. Soc.. 2009, 29(4):751-756 DOI:10.1016/j.jeurceramsoc.2008.06.025

Microstructural, structural and electrical properties of La³+-modified Bi₄Ti₃O₁₂ ferroelectric ceramics

Abstract

Bi_4−xLa_xTi₃O₁₂ (BLT) ceramics were prepared and studied in this work in terms of La³⁺-modified microstructure and phase development as well as electrical response. According to the results processed from X-ray diffraction and electrical measurements, the solubility limit (x_L) of La³⁺ into the Bi₄Ti₃O₁₂ (BIT) matrix was here found to locate slightly above x = 1.5. Further, La³⁺ had the effect of reducing the material grain size, while changing its morphology from the plate-like form, typical of BIT ceramics, to a spherical-like one. The electrical results presented and discussed here also include the behavior of the temperature of the ferroelectric–paraelectric phase transition as well as the normal or diffuse and/or relaxor nature of this transition depending on the La³⁺ content.

... 10时, 晶粒取向趋近于一致, 部分晶粒发育不完全, 晶粒尺寸变小, 且尺寸分布变宽, 产生了许多细小晶粒, 可能是由于La的掺杂抑制了晶粒的长大, 这与顾大国等^[12]在La对CaBi₄Ti₄O₁₅掺杂改性时的发现是一致的 ...

1998

2.108

0.0

... Subbarao等^[13]曾指出, 居里温度的高低与取代离子的半径和电负性有关, 随取代离子半径增大而降低, 随取代离子电负性升高而增加, 在铋层状结构化合物中, 类钙钛矿层中A位离子半径越大其居里温度越低, A位阳离子半径的增大(偏离类钙钛矿亚结构)导致晶格变形, 相应的沿着极化轴(ab轴)原子的位移变小, 因此达到高温结构的能量减少^[14,15] ...

2004

0.0

2000

2.107

0.0

2009

2.072

0.0

... 3 eV, 与某些铋层状以及钙钛矿铁电梯带隙(均源于TiO₆八面体带隙)的1/2接近^[16,17], 对应了材料的本征导电 ...

2008

2.107

0.0

... 3 eV, 与某些铋层状以及钙钛矿铁电梯带隙(均源于TiO₆八面体带隙)的1/2接近^[16,17], 对应了材料的本征导电 ...