Developments of Piezoelectric Actuators by Using Envirnmentally Gentle Lead-Free Piezoelectric

从环境保护的角度来看，最近对无铅材料提出了要求。例如，注册将在欧盟强制执行，作为关于电子电气设备废物（WESTERN）、有害物质限制（RoHS）和报废车辆（ELV）的指令草案。因此，无铅压电材料作为替代Pb基Pb（Zr，Ti）O3（PZT）陶瓷的新材料受到广泛关注。为了取代PZT系统，有必要对各种应用所需的压电性能进行划分，并开发相应的每个应用。例如，钙钛矿型陶瓷似乎适合于致动器和高功率应用。在本计画中，我们尝试使用无铅压电陶瓷来研制压电驱动器。具有钙钛矿结构的无铅压电陶瓷候选材料有BaTiO 3（BT）、（Bi 1/2Na 1/2）TiO 3（BNT）、（Bi 1/2K 1/2）TiO 3（BKT）。 ...更多信息 本文研究了BNT、BKT和BT三元固溶体的介电、铁电和压电性能，并对BNT、BKT和BT三元固溶体的介电、铁电和压电性能进行了研究。x（Bi_<1/2>Na_<1/2>）TiO_3-y（Bi_<1/2>K_<1/2>）TiO_3-zBaTiO_3（x+y+z=1）[BNBKy：z（x）]作为驱动器的候选材料进行了研究。BNT基铁电体通常在200℃以下发生第二相变，在此温度以上没有压电活性。在本项目的第一年，我们得到了最佳的组成BNBK 4：1（0.852），在<33>准同型相界（MPB）附近，d_ =190 pC/N，T_c=300℃。但第二相变温度（T_2=120℃）低于我们的目标温度。第二年，我们再次尝试研究三组分系统。最后，<33><33>对于BNBK 2：1（0.78），k_和d_分别为0.474和140.2pC/N，而对于BNBK 2：1（0.72），k_和d_分别为0.462和127.9pC/N。三元固溶体陶瓷压电性能的温度依赖性表明，当温度高于200℃时，第二相变温度越高，压电活性越高。该固溶体是无铅压电多层陶瓷驱动器的一种上级候选材料。少

Lead-free materials are recently demanded from the viewpoint of environmental protection. For example, the registration will be enforced in the EU as the draft Directives on Waste form Electrical and Electronic Equipment(WEEE), Restriction of Hazardous Substances(RoHS) and End-of Life Vehicles(ELV). Therefore, lead-free piezoelectric materials have been widely attracting attention as new materials in place of Pb-based Pb(Zr, Ti)O3 (PZT) ceramics. To replace PZT systems, it is necessary that required piezoelectric properties for various applications were divided and were developed the corresponding each application. For example, the perovskite type ceramics seem to be a suitable for actuators and high power applications. In this project, we try to develop piezoelectric actuators by using envirnmentally gentle lead-free piezoelectric ceramics. Candidate materials with the perovskite structure for lead-free piezoelectric ceramics are BaTiO3(BT), (Bi1/2Na1/2)TiO3(BNT), (Bi1/2K1/2)TiO3(BKT) … More and KNbO3(KN) etc. The desiable properties for piezoelectric actuators should show at least the piezoelectric strain constant, d33>300 pC/N and the Curie tempearature, Tc>200℃.Dielecric, ferroelectric and piezoelectric properties of a solid solution based on three components of BNT, BKT and BT, that is, x(Bi_<1/2>Na_<1/2>)TiO_3-y(Bi_<1/2>K_<1/2>)TiO_3-z BaTiO_3(x+y+z=1)[BNBKy:z(x)] are studied as a candidate for the actuator applications. BNT-based ferroelectrics usually have the second phase transition below 200℃ and show no piezoelectric activities above this temperature. In first year of this project, we had the best composition BNBK4:1(0.852) with d_<33>=190 pC/N and T_c=300℃ near the morphotropic phase boundary(MPB). However, the second phase transition temperature (T_2=120℃) is lower than that of our goal. In second year, we again tried to study the three component system. Finally the k_<33> and d_<33> are 0.474 and 140.2 pC/N for BNBK2:1(0.78) and more 0.462 and 127.9 pC/N for BNBK2:1(0.72), respectively. Temperature dependences of piezoelectric properties of the three-component solid solution ceramics display that piezoelectric activities keep up to higher than 200℃ with the higher second phase transition. This solid solution seems to be a superior candidate material for lead-free piezoelectric multilayer ceramic actuators. Less