DEVELOPMENT OF HIGH PERFORMANCE STRESS SENSOR USING SEMICONDUCTING BARIUM TITANATE THIN WIRES WITH GIANT PIEZORESISTIVE EFFECTS

本研究的目标将澄清半导体barium titanate ceramics中的压电效应的机制，并使生产高性能压力传感器使用barium titanate thin wires具有单一谷物边界结构的一个显著的大压电效应在房间温度中的作用。获得的结果将被总结为以下：（1）半导体屏障钛薄陶瓷导线的制备：我们成功地生产半导体屏障钛薄陶瓷电线，具有10-20微米的直径，稳定于单粒颗粒结合在一起的系列中，通过从泥浆中绘制绿色纤维，在空气中1370 ° C时观测到的巨型压电效应：在Gage因子中超过10^7的极大压电效应（定义为每应变的抵抗性变化比率）被观察到一些单一谷物边界形成半导体屏障钛薄陶瓷电线生产中的一部分 ... More D.3）对机械压力下90度域墙壁运动的分析：我们直接观察到90度域墙壁在拉伸和压缩压力下如何移动BaTiO_3陶瓷导线。在这次实验中，我们发现，仅仅是一个90度的域墙到达了一个谷物边界，与谷物边界中的域形态学的即时变化有关，而谷物边界的抵抗力则被简单地改变了。这是第一次确认，半导体屏障钛陶瓷中的皮氮主义与谷物边界中的域形态学变化直接相连。（4）皮氮主义机理的分析：我们能够成功地确定两个铁电域的固有极化的方向，在机械压力下的一个单一颗粒移动到一个90个域墙。从获得的结果中，已经发现了半导体钡钛陶瓷中的皮氮主义的计量学可以通过颗粒边界上的表面电荷补偿模型来解释。5）恢复发布用于生产高性能压力传感器装置的程序：我们制造了一个原型压力传感器装置，使用半导体屏障钛薄陶瓷电线，以展示在房间温度下的较大压电效应，并确认他们的压力传感器功能，作为预期的几个问题，因此可再生性仍然存在。Less（低）

The objective of this study is to clear the mechanism of the piezoresistive effect in semiconducting barium titanate ceramics and to establish a procedure for producing high-peformance stress sensors using barium titanate thin wires with a single grain boundary structure, which exhibit a significantly large piezoresistive effect at room temperature.The obtained results are summarized as follows :1) Preparation of semiconducting barium titanate thin ceramic wires : We succeeded in producing semiconducting barium titanate thin ceramic wires, with a diameter of 10-20 μm, consisting of single grains joined together in series by drawing green fibers from slurry, followed by sintering at 1370℃ in air.2) Observation of giant piezoresistive effects : An extremely large piezoresistive effect of more than 10^7 in gauge factor (defined as the resistance change ratio per strain) was observed for some of the single grain boundaries formed in semiconducting barium titanate thin ceramic wires produce … More d.3) Analysis of the 90゜ domain wal motion under mechanical stresses : We directly observed how 90゜ domain walls move in a BaTiO_3 ceramic wire under tensile and compressive stresses with a polarizing microscope. In this experiment, we found that just as a 90゜ domain wall arrived at a grain boundary, associated with an instantaneous change of the domain morphology in the vicinity of the grain boundary, the grain boundary resistivity drastically changed. It has been for the first time confirmed that the piezoresistivity in semiconducting barium titanate ceramics is directly connected with the change of the domain morphology in the vicinity of grain boundaries.4) Analysis of the piezoresistivity mechanism : We were able to successfully determine the direction of spontaneous polarization in the two ferroelectric domains adjacent to a 90゜ domain wall moving in a single grain under mechanical stresses. From the obtained results it has been found that the meachanism of the piezoresistivity in semiconducting barium titanate ceramics can be interpreted by a surface charge compensation model by spontaneous polarization at grain boundaries.5) Est ablishment of a procedure for producing high-performance stress sensor devices : We made prototype stress sensor devices using semiconducting barium titanate thin ceramic wires, which exhibit a large piezoresistive effect at room temperature, and confirmed their stress sensor function working as expected though some problems such as reproducibility remain. Less