ISSN:
1662-8985
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Changes in crystal phase and electrical properties of oxides composed of Mn, Co, and Niwith the molar ratios of 5:2:1 and 3:3:1 were investigated. Starting oxides were fired from 250°C to800°C, then maintained at prescribed temperatures for 3 h in air. In the 5:2:1 specimen, a monophaseconsisting of a cubic spinel oxide that is important to electrical conductivity was obtained at firingtemperature of 800°C. In the 3:3:1 specimen, the monophase was obtained at temperatures rangingfrom 600°C to 800°C. Electrical resistance decreased exponentially with increasing temperature forall specimens fired at temperatures ranging from 250°C to 800°C, indicating that the oxides haveintrinsic thermistor characteristics with negative temperature coefficient (NTC). The temperaturedependence of the thermistor constant (B value) necessary for practical application was considered tobe related to the existence ratio of cubic spinel-type and ilmenite-type structures and the latticeconstant of the cubic spinel-type structure. The electrical conduction was stabilized by annealing atprescribed temperatures for more than 720 minutes
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.29-30.359.pdf
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