Design for high-performance functional composite thermistor materials by glass/ceramic composing
- PDF / 334,602 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 55 Downloads / 165 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Design for high-performance functional composite thermistor materials by glass/ceramic composing D.J. Wang,a) J. Qiu, Z.L. Gui, and L.T. Li State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, People’s Republic of China (Received 10 November 1997; accepted 2 April 1999)
A negative temperature coefficient–positive temperature coefficient (NTC-PTC) composite thermistor with high performance was designed by glass/ceramic composing. The material exhibited low resistivity and a large negative temperature coefficient of resistivity. The minimum resistivity was the magnitude of 102 ⍀ cm, and the negative temperature coefficient of resistivity was better than −3% °C−1. The results showed that the large negative temperature coefficient of resistivity was closely related to the glass phase, and the NTC-PTC functional composite material was a kind of grain-boundary–controlled material. I. INTRODUCTION
Composit thermistors are material that exhibit both negative temperature coefficient (NTC) and positive temperature coefficient (PTC) characteristics in different ranges of temperature. Composite thermistor can fulfill multiple functions such as temperature control and overflow protection, among others, and therefore research on its properties has great practical significance.1,2 Strontium-lead titanate ceramic is one of the composite thermistor materials.3–7 The previous study of strontiumlead titanate materials by a conventional solid-state reaction process has the obvious disadvantage of poor reliability, which led to the inconclusive relationship between composition and property for the ceramics. For the above reasons, the systematic research on (Sr,Pb)TiO3 ceramics was made by a liquid chemical process in order to prepare a high-performance NTCPTC composite thermistor. In the research, (Sr,Pb)TiO3 ceramics with typical PTC characteristics comparable to that of conventional BaTiO3 ceramics was first announced.8–10 However, the materials exhibited a weak NTC effect, and it was surprisingly difficult to prepare NTC-PTC materials with strong NTC behavior by a chemical process. In this paper, the second phase, which related to NTC behavior, was composited from the semiconducting strontium-lead titanate PTC materials in order to obtain strong NTC behavior in the original PTC materials below the Curie temperature. The schematic diagram of the design idea is shown in Fig. 1. It is well known that conventional NTC thermistor materials consist of the composite oxides of transition metal such as Mn, Co, Ni, and Fe, among others.11 If the a)
Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 14, No. 7, July 1999
http://journals.cambridge.org
Downloaded: 25 Mar 2016
composite of the conventional NTC and PTC materials is considered, the trace amount of transition metal ions can serve as the acceptor in the PTC materials and can improve the PTC behavior
Data Loading...
