Lead‐free potassium sodium niobate (K0.5Na0.5)NbO3 thin films on Pt(111)/TiO2/SiO2/Si substrates have been prepared from the acetate–alkoxide‐based precursor solutions with the stoichiometric composition and with 5 or 10 mol% excess of sodium or potassium acetate. Upon heating to 750°C, the films crystallize in pure perovskite phase. The increasing amount of alkali excess in solutions increases the degree of {100} orientation and it influences the nucleation and growth processes in the films. The microstructure of about 250 nm thick films prepared from the stoichiometric and 5 mol% excess solutions consists of equiaxed grains of about 50 nm across, whereas the grain size in the about 220 nm thick films prepared from the 10 mol% excess solutions is about 200 nm. The energy dispersive X‐ray spectroscopy revealed that the alkali excess in precursor solutions contributed to a higher level of chemical homogeneity of the films on the micrometer scale. The chemical composition of the films prepared from the 5% potassium‐excess solution was closest to the (K0.5Na0.5)NbO3 composition among all the samples as a result of more pronounced potassium losses upon heating. These films had the room temperature values of dielectric permittivity, dielectric losses, remnant polarization, and coercive field measured at 1 kHz 610, 0.015, 8 μC/cm2, and 80 kV/cm, respectively.

The time for which each contacting body is exposed to a tribological contact affects its interface temperature, third-body and tribofilm formation, and, as a result, the overall tribological behaviour, which may be particularly relevant with very dissimilar material pairs. This work focuses on the tribological properties of unreinforced polyamide (PA6) in selfmated contacts or against steel (SS) as a stationary (SS/PA6) or a moving contact (PA6/SS) body under dry-sliding conditions. Moreover, the effects of the contact pressure and the sliding velocity were investigated for these contacts. In addition, the contact conditions were carefully controlled with measurements of the specimen's surface temperature using an infrared camera. The results show that the tribological behaviour indeed depends significantly on the contact configuration. The tribological properties of the stationary steel pin sliding against a rotating polymer disc (SS/PA6), as well as of a self-mated PA6/PA6 contact, depended substantially on the contact conditions used. In contrast, the contact configuration of a stationary PA6 pin sliding against a rotating steel disc (PA6/SS) showed only a negligible effect on changes in the sliding speed and the load. Moreover, this was clearly the bestperforming contact in the study and the beneficial effect is explained by the ability of a rotating disc to remove the heat from the contact zone and, consequently, to lower the temperatures generated in the tribological contact.

The testing procedures and reported tribological performance of polymer gears, which are seeing ever-increasing use by industry, still lack consistency and detail. One of the key parameters that affect a polymer's mechanical properties, interface contact conditions and, consequently, the wear and fatigue behaviour, is the temperature. Temperature is well known to have a critical influence on all polymers, much more so than on metals or other materials. However, the temperatureseven for the same load and velocityvary greatly with testing devices, gear sizes and shapes, surrounding environment, as do the cooling and heating rates. Moreover, the temperature, either root, flank or bulk, also varies with the operating conditions, meaning that even in the same S-N curve data at different stresses we actually obtain different temperatures. This suggests that the results from different tests and even different load levels, which are not temperature controlled, cannot be directly compared due to the important influence of the temperature on the polymers. This work presents the results of POM gears tested against steel gears under well-controlled temperature conditions, providing various S-N curves obtained at 30 ˚C, 50 ˚C and 70 ˚C that were kept constant at the gear root for three torque values (1.0 Nm, 1.2 Nm and 1.4 Nm), and these are compared to data obtained under conditions that are typically considered to be "room temperature", which is in fact an uncontrolled temperature. The results confirm the important effect of the temperature on the fatigue life of POM gears, i.e., when kept at low temperature (30 °C), the fatigue life of POM gears is greatly improved.

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