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The pressure sensing properties of nanocomposite SnO 2 , TiO 2 , and TiO 2 /ZnO thick film capacitors with interdigitated electrodes are investigated. To form the dielectric layers, the metal oxides powders were respectively mixed with isopropanol, wet ball milled for 24 h, then the mixtures were dried at 120 °C and further the powders were placed under 2 tonnes of pressure to form pellets, which were fired at 1250 °C (rate of 5 °C/min) in a vacuum of 6 × 10 −3 mbar for 5 h, followed by cooling (rate of 3 °C/min). After firing, the resultant nanopowders were mixed with 7 wt.% of polyvinyl butyral (binder) and suitable amount of ethylenglycolmonobutylether (solvent) to form the pastes. These were screen-printed over the Ag electrodes on alumina substrates to form SnO 2 , TiO 2 , and TiO 2 /ZnO capacitor pressure sensors accordingly. The evaluation of pressure sensing properties of these sensors was performed using a HP 4192A Impedance Analyser, which recorded the changes in the values of the capacitances under different mechanical stresses. At the applied load of 5 kPa, the response times of 2.5 s, 5.6 s and 4 s were recorded for SnO 2 , TiO 2 , and TiO 2 /ZnO sensors, respectively. In addition to instant response times, these pressure sensors have the advantage of being reusable, as their electrical properties were restored to the original value after annealing for 2 h at 80 °C. Moreover, one year later after the initial testing, the sensors were still operational and produced similar time responses to pressure.

The electrical properties of PVDF thick film capacitors under gamma radiation are investigated. To increase the conductivity of the films, they were filled with 4 and 6 wt.% of carbon, which is close to the percolation threshold. Screen-printing was used for film fabrication. All films were exposed to a disk-type 137 Cs source with an activity of 370 kBq. Changes in I – V characteristics were measured after each exposure dose. A tenfold increase in the values of current was recorded after a dose of 228 μGy for C-PVDF films with a thickness of 23.97 μm and 6 wt.% carbon doping. A higher dose of 342 μGy resulted a decrease in the values of current. Thicker films showed an increase in the values of current with irradiation to a dose of 798 μGy. PVDF + carbon system has potential applications in low-dose radiation dosimetry. The high current induced by radiation caused heating and electroforming of the device, due to the metal inclusions from the Ag contact material. It was noticed that as-printed films of 23.97 μm in thickness, tend to electroform at about 12 V, whereas films irradiated with 171 μGy showed a strong electroforming effect at a lower voltage of 5 V. For that reason, proper design of dosimetry systems is essential to eliminate such effects. Gamma radiation sensitivity of counterpart PVDF thick films with 4 wt.% carbon doping was studied via capacitance-dose measurements in real time, since these samples were less conductive. Irradiation of this sensor with doses from 1.15 to 2.5 mGy caused a considerable monotonic increase in the values of its capacitance from 2.92 to 12.37 pF. Accordingly, sensors with 4 wt.% of carbon could sustain higher radiation doses, but had poor sensitivity to radiation of lower level.

The properties of the materials undergo changes by the influence of γ-rays. The degree of these changes could serve as a measure of the received radiation dose. Deep understanding of physical properties of the materials under the influence of radiation is vital for the effective design of devices for radiation-sensing applications. Mixing oxides in various proportions was found to control the radiation-sensing properties of the semiconductor films in terms of their sensitivity to γ-radiation exposure and working dose region.

Throughout this work radiation-induced changes in the optical, electrical and structural properties of mixed and carbon filled metal oxides were studied. Oxides such as NiO, CeO2, TeO2, In2O3, SiO and MnO in the form of thin and thick films were used. The properties of the materials undergo changes by the influence of γ-rays. The degree of these radiation-induced changes serves as a measure of received radiation dose. Deep understanding of physical properties of the materials under the influence of radiation is vital for the effective design of dosimeters. In this work all films were exposed to a disk-type 137Cs source with an activity of 370 kBq. Carbon filling and mixing oxides in various proportions was found to control the properties of semiconductor films in terms of their susceptibility to radiation exposure. For example, planar NiO thick film structures with Ag interdigitated electrodes showed an increase in the values of current with the increase in radiation dose up to 171 μSv. Doping of NiO thick films with 0.1 wt.% of carbon resulted in larger increments in the values of current and the increasing the working range to 2720 μSv. The possibility to fabricate a device that would satisfy the requirement of particular application, in this case the sensitivity to γ-radiation exposure and working dose region, was experimentally demonstrated.

Zinc and iron oxide thick film gas sensors were fabricated using screen-printing technology on glass substrates that had silver interdigitated electrodes. The sensor was used to detect methanol, ethanol and propanol with a concentration range of 0–8000 ppm. Using the formula to calculate a change in resistance, ΔR = Rgas − Rair, resistance was seen to increase linearly alongside increasing concentrations of the gas vapours. The sensor showed the highest sensitivity to propanol followed by ethanol and methanol when the operating temperature was 25 °C. The sensitivities (slope of graphs) of methanol, ethanol and propanol changed from 0.07, 0.5, and 3.54 to 0.075, 0.115, and 0.5 Ω/ppm when the operating temperature was increased from 25 to 50 °C. The response/recovery times of the sensor for 4000 ppm at room temperature were, 10/10, 15/20 and 40/70 s for methanol, ethanol and propanol, respectively. X-ray diffraction (XRD) was used to examine the final composition of the film, while scanning electron microscopy (SEM) was used to examine the final composition of grain size. The final composition has two phases: ZnO and ZnFe2O4

Throughout this work tellurium dioxide (TeO2), indium oxide (In2O3), silicon monoxide (SiO), nickel oxide (NiO) and LaFeO3 perovskite and their mixtures in different proportions in the forms of thin and thick films were used as materials for the radiation sensing layers. Detection of radiation was performed based on the fact that both electrical and optical properties of the materials undergo changes upon the exposure to gamma radiation. It was found that the optical band gap values decreased with the increase in radiation dose. Influence of radiation resulted in significant alterations of current–voltage characteristics in both thin and thick film devices.

Thin-film strain gauges of the mixed oxide Bi2O3-V2O5 have been deposited on insulated stainless steel substrates. The thin-film gauges are insulated from the steel by application of dielectric layers printed using thick-film techniques. Various strain gauge parameters are analysed, including linearity, hysteresis, repeatability and temperature effects. Comparisons have also been made with similar gauges deposited on glass. It has been observed that the thin-film strain sensor deposited on steel performs much better than the one deposited on glass in terms of maximum applicable strain, hysteresis and linearity. However, the film on glass is much more sensitive than the one deposited on steel. The lower-sensitivity of the sensor on steel is attributed to the increased thickness of the deposited resistor and the poorer surface characteristics of the thick-film dielectric layers. The d.c. conductivity variation at high temperatures has also been studied and it has been observed that freeband conduction takes place at these temperatures.