Multilayer thick-film structures based on spinel ceramics

摘要

Temperature-sensitive thick films based on spinel-type semiconducting ceramics of different chemical composition Cu_(0.1)Ni_(0.1)Co_(1.6)Mn_(1.2)O_4 (with p~+-types of electrical conductivity), Cu_(0.1)Ni_(0.8)Co_(0.2)Mn_(1.9)O_4 (with p-types of electrical conductivity), and their multilayers of p~+-p and p-p~+-p structures were fabricated and studied. These thick-film elements possess good electrophysical characteristics before and after long-term ageing test at 170 ℃. It is shown that degradation processes connected with diffusion of metallic Ag into grain boundaries occur in one-layer p- and p~+-conductive thick films. The p~+-p structures were of high stability, the relative electrical drift being no more than 1%. Positron trapping processes in so-called "free" thick-film structures based on spinel-type Cu_(0.1)Ni_(0.8)Co_(0.2)Mn_(1.9)O_4 ceramics are studied. It is shown that two-state positron trapping model is appropriate for an adequate description of changes caused by additional glass phase in these materials. The observed behaviour of defect-related component in the fit of the experimentally measured positron lifetime spectra for thick films in comparison with bulk ceramics testifies in favour of agglomeration of free volume entities during technological process.