ANALYSIS ON HIGH-TEMPERATURE-RESISTANT CHARACTERISTICS OF LACRNIMNO CERAMICS

The investigations carried out by extensive stability tests on LaCrO3, NiMn2O4 and their composite materials have revealed that composite ma terials are greatly superior to single-phase materials in stability. I n this paper, the causes of resistance variation on single phase mater ials during ageing are analysed applying the defect chemistry theory. The research suggests that the reduction of oxygen vacancies concentra tions, which result from the absorbed oxygen in the surface and pores of ceramics diffused gradually into grains, decreases the resistivity of p-type semiconductor ceramics LaCrO3 and increases that of n-type s emiconductor ceramics NiMn2O4. Thus, it is concluded that the excellen t high-temperature-resistant characteristics of composite electroceram ics are the result of the compensation effect of composite materials. (C) 1998 Elsevier Science S.A. All rights reserved.