Microstructures and PTC-Mechanism in Pb TiO_3-TiO_2 PTC Ceramics for High Temperature Applications

高温应用 Pb TiO_3-TiO_2 PTC 陶瓷的微观结构和 PTC 机制

• 批准号: 01550542
• 负责人: OKADA Masuo
• 金额: $ 1.73万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1989
• 资助国家: 日本
• 起止时间: 1989 至 1991
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-01550542/
• 关键词: PbTiO_3-TiO_2 Ceramics; PTC Thermistor; Control of Curie Temperature; PTCR Mechanism; Interfaces between Ferroelectric and Non-Ferroelectric; Additions of Oxides of Transitional Elements; 測定雰囲気; PbTiO_3-TiO_2セラミックス; 強誘電体-非強誘電体界面

The purpose of the present studies is to establish the preparation techniques of PbTiO_3-TiO_2 ceramics as PTC thermistors, and to clarify the PTCR mechanisms. The obtained results are summarized as follows ;1. Optimum conditions of preparing techniques are established. Optimum compositions are PbTiO_3-(30-80)mol%TiO_2, and which are fired at 975ﾟC-1025ﾟC for 2 hr in Ar atmosphere.2. Heating temperatures of the thermistors can be controlled by lowering the Curie temperature. of the system with the addition-of SrTiO_3. For an example, the Curie temperatures of the samples with 30%SrTiO_3 addition, is around 350ﾟC.3. The addition of oxides of transition metals increased the PTCR properties, and furthermore improved their stabilities.4. Present studies find that the PTCR properties are originated not only from the interfaces of ferroelectric PbTiO_3 grains, but also interfaces of PbTiO_3 and TiO_2 grains. This results are obtained by the direct - observations of temperature resistivities properties on the samples where Pt electrodes are connected with the coarse grains of PbTiO_3 and TiO_2.The atmosphere for resistivity-temperature measurement affects PTCR properties, which are disappeared with vacuum atmosphere. Then the oxygen plays important role in originating the PITCR properties.

本研究旨在建立PbTiO_3-TiO_2系PTC热敏陶瓷的制备工艺，并阐明其PTCR机理。所得结果总结如下：1.确定了最佳制备工艺条件。最佳组成为PbTiO_3-（30-80）mol%TiO_2，在Ar气氛中于975 ℃-1025 ℃烧成2小时.可以通过降低居里温度来控制热敏电阻的加热温度。SrTiO_3的加入对体系的稳定性有一定的影响。例如，添加30%SrTiO_3的样品的居里温度约为350 ℃。过渡金属氧化物的加入提高了PTCR的性能，并进一步改善了其稳定性.研究发现，PTCR性能不仅来源于PbTiO_3晶粒间的界面，还来源于PbTiO_3和TiO_2晶粒间的界面。这一结果是通过直接观测Pt电极与PbTiO_3和TiO_2粗颗粒相连接的样品的温度电阻率特性得到的。电阻率-温度测量气氛对PTCR特性有影响，但在真空气氛下这种影响消失。氧在PITCR性能的形成中起着重要的作用。