Nanocomposites and nanomaterials

Features of humidity-sensitive thick films 
based on nanoporous ceramics
H. Klym1, I. Hadzaman2, I. Vasylchyshyn1

1Lviv Polytechnic National University, Bandery str., 12, Lviv-79013, Ukraine 
E-mail: halyna.i.klym@lpnu.ua; klymha@yahoo.com 
2Drohobych Ivan Franko State Pedagogical University, Ivan Franko str., 24, Drohobych-82100, Ukraine

In this work electrophysical, structural and topological investigations of humidity-sensitive thick films based on nanoporous MgAl2O4 ceramics. The paste for screen-printing of thick films was obtained on roller paste by mixing MgAl2O4 ceramic powder (58 %), organic solvent and organic bond (30 %), lead-free organic oxide powder (8 %) and Bi2O3 (4 %) [1]. It is shown that the disadvantage of obtaining paste is their high viscosity. In order to eliminate this disadvantage, corrections were made for the content of Bi2O3, glass MB-60, organic bond SM-2 and pine oil. The obtained thick films exhibit typical features of spinel structure with crystallographic parameters, it has a good surface morphology, as well as high values ​​of humidity sensitivity.
The investigated thick films were characterized by good contacts with a sufficiently reliable overlap areas of the functional film with the contact pads of conductive films. The thick films have a sufficiently high humidity sensitivity in the range of RH from 55 to 99%, which is expressed in a relative change in their electrical resistance by 1...1.5 orders of magnitude. 
Their significant drawback is the limited sensitivity of low values ​​of relative humidity as well as the emergence of hysteresis in the measuring cycles of the electric resistance in the case of increase and decrease of explosives as a result of the degradation test (the actual exposure of samples for 240 hours at 40 °C and RH = 95 %). This effect, evidently, is due to the imperfection of the porous structure of thick films based on MgAl2O4 ceramics in the transition region between the thick films and substrate.

1.	Klym H., Hadzaman I., Shpotyuk O., Brunner M. Integrated thick-film nanostructures based on spinel ceramics. Nanoscale research letters, 2014, 9(1), 1-6.