The pellets were sintered in a special regime with maximal temperature T s = 1,300°C for 5 h. Temperature-sensitive Cu0.1Ni0.1Co1.6Mn1.2O4/Cu0.1Ni0.8Co0.2Mn1.9O4-based pastes were prepared by mixing powders of basic ceramics (72.8% of sintered bulk ceramics were preliminarily destroyed, wet-milled, and dried) with ecological glass powders (2.9%) without PbO, inorganic binder Bi2O3 (2.9%), and organic vehicle (21.4%). The next content was used for the preparation of humidity-sensitive thick-film pastes: MgAl2O4-based ceramics (58%), Bi2O3 (4%), ecological glass (8%), and organic vehicle (30%). The pastes were printed on alumina substrates (Rubalit 708S, CeramTec, Plochingen,
Germany) using a manual screen printing device equipped with selleck inhibitor a steel screen. Then, thick films were sintered in PEO-601-084 furnace at 850°C [20, 23]. The insulating (i-type) paste in two layers was printed on temperature-sensitive TPCA-1 molecular weight (p-type) thick-film layer previously formed on alumina substrate. In contrast to previous works [21, 23], the p+-conductive paste was formed on humidity-sensitive i-type layer as conductive layer. Then, these structures were sintered in the furnace. The topological scheme of integrated
p-i-p+ thick-film structure is shown in Figure 1. Figure 1 Topological scheme of integrated thick-film p-i-p + structure. The microstructure of the sintered temperature-sensitive ceramics was probed using an electron microscope JSM-6700 F (JEOL Ltd., Akishima, Tokyo, Japan), BAY 1895344 mouse cross-sectional morphology of the samples being tested near the surface (0- to 70-μm depth) and chip centers. Scanning electron microscopy (SEM) investigations for bulk humidity-sensitive ceramics and thick-film structures were performed using
LEO 982 field emission microscope (Carl Zeiss AG, Oberkochen, Germany). The pore size distribution of bulk semiconductor and dielectric ceramics in the region from 2 to 1,000 nm was studied using Hg-porosimetry (POROSIMETR find more 4000, CARLO ERBA STRUMENTAZIONE, Hofheim am Taunus, Germany). The electrical resistance of thermistor thick films was measured using temperature chambers MINI SUBZERO, Tabai ESPEC Corp., Japan, model MC-71 and HPS 222. The humidity sensitivity of thick-film structures was determined by measuring the dependence of electrical resistance R on relative humidity (RH) of the environment. The electrical resistance was measured in the heat and humidity chamber PR-3E (Tabai, Osaka, Japan) at 20°C in the region of RH = 20% to 99%. The electrodes were attached to connecting cables of M-ohmmeter at fixed current frequency of 500 Hz (with the aim of avoidance of polarization of adsorbed water molecules). In addition, the degradation transformation at 40°С and RH = 95% for 240 h was carried out in order to study sample stability in time. The maximal overall uncertainties in the electrical measurements did not exceed approximately ± (0.02 to 0.