Developments of Piezoelectric Actuators by Using Environmentally Gentle Lead-Free Piezoelectric Ceramics

近年来，随着欧盟《废旧电子电气设备(WEEE)、有害物质限制(RoHS)和报废车辆(ELV)指令草案》等法规的出台，从环保的角度对无铅压电材料提出了强烈的要求。用钙钛矿结构替代铅基无铅压电陶瓷的候选材料有BaTiO_3(BT)，(Bi1/2&gt；1/2&gt；)TiO3(BNT)，(Bi1/2&gt；K_&lt；1/2&gt；1/2&gt；)TiO_3(BKT)和这些固溶体，以及更多的KNbO_3(KN)基固溶体等。压电致动器的理想性能应该至少表现出压电应变常数d_&lt；33&gt；&gt；300pC和居里温度T_c，或退极化温度T_d，&gt；200℃。本课题研究了钙钛矿结构和铋层状结构…取向磁控织构铁电陶瓷的介电、铁电和压电性能。更适用于压电致动器和压电陶瓷谐振器。以Bi4Ti3O12为模板，采用反应模板法制备了具有钙钛矿结构的0.9(Bi_&lt；1/2&gt；K_&lt；1/2&gt；)TiO_3-0.1BaTiO_3(BKTBT10)。此外，利用织构复合材料制备了多层压电致动器，并对其性能进行了评价。BKT-BT10的退偏温度Td高于250℃。织构和磁畴控制的BKT-BT-BT10的电场感应应变S是无取向的1.5倍，动态压电应变常数D33为168pC/N。织构和磁畴控制的这种固溶体陶瓷有望成为无铅压电多层陶瓷驱动器的优良候选材料。采用热锻(HF)法制备了BLSF(BLSF)SrBi2Nb&lt；2-x&GT；VxO9(SBNV-x)陶瓷。针对陶瓷谐振器的应用，研究了SBNV-x在不同振动模式下的压电性能与温度的关系，特别是测量了共振和反共振频率的温度系数(TC-f)作为晶体取向轴的函数。由于BLSF中各向异性的起源，TC-f在a-b轴上降低。(33)模的电品质因数Q_c=66，Q_m=2200和TC-f=16.5ppm/℃，(15)模的Q_c=21.6，Q_m=4600和TC-f=27.7ppm/℃。这些结果表明，颗粒取向的SBNV陶瓷可以以无铅压电谐振器的形式商业化。较少

Recently lead-free piezoelectric materials are strongly demanded from the viewpoint of environmental protection by the registration such as the draft Directives on Waste form Electrical and Electronic Equipment (WEEE), Restriction of Hazardous Substances (RoHS) and End-of Life Vehicles (ELV) in EU. Candidate materials with the perovskite structure for lead-free piezoelectric ceramics in place of Pb-based Pb (Zr, Ti)O_3 (PZT) seem to be BaTiO_3 (BT), (Bi_<1/2>Na_<1/2>)TiO_3 (BNT), (Bi_<1/2>K_<1/2>)TiO_3 (BKT) and these solid solutions, and more KNbO_3 (KN)-based solid solutions etc. The desirable properties for piezoelectric actuators should show at least the piezoelectric strain constant, d_<33>>300 pC/N and the Curie temperature, Tc, or the depolarization temperature, T_d, >200℃. In this project, dielectric, ferroelectric and piezoelectric properties of grain-oriented and domain controlled textured ferroelectric ceramics with perovskite structures and bismuth layered-structures (BLSF) … More to apply to piezoelectric actuators and piezoelectric ceramic resonators.1. Grain oriented 0.9(Bi_<1/2>K_<1/2>)TiO_3-0.1BaTiO_3 (BKT-BT10) with perovskite structure was fabricated by a reactive template grain growth (RTGG) method using the template of Bi4Ti3O12. And more, multilayer type piezoelectric actuators using the textured composition were fabricated and the actuator properties were evaluated. The depolarization temperature, Td, of BKT-BT10 is higher than 250℃. The electric field induced strain, S, of textured and domain controlled BKT-BT10 is 1.5 times higher than that of non-oriented, and the dynamic piezoelectric strain constant, d33, is 168 pC/N. Textured and domain controlled this solid solution ceramics seem to be a superior candidate material for lead-free piezoelectric multilayer type ceramic actuators.2. Domain controlled bismuth layer-structured ferroelectric (BLSF) SrBi2Nb_<2-x>V_xO_9(SBNV-x) ceramics were fabricated by the hot-forging (HF) method. Temperature dependences in the various vibration modes of piezoelectric properties of SBNV-x were evaluated for ceramic resonator applications, especially, temperature coefficient of resonant and antiresonant frequencies (TC-f) were measured as a function of the crystal orientation axis. The TC-f was lowered in the a-b axis because of the origin of an anisotropy in BLSF. Electrical quality factor, Q_e, the mechanical quality factor, Q_m, and TC-f of grain-oriented (HF) SrBi_2Nb_<1.95>V_<0.05>O_9 (SBNV-0.05) were Q_c=66, Q_m=2200 and TC-f=16.5 ppm/℃ for (33)-mode, and Q_c=21.6, Q_m=4600 and TC- f=27.7 ppm/℃ for (15)-mode, respectively. These results indicate that grain oriented SBNV ceramics can be commercialized in the form of lead-free piezoelectric resonators. Less