Obtaining the high performance PTC thermistors based on barium titanate

PTC thermistors based on semiconducting barium titanate are devices with large applications in electrical and electronic engineering, automotive industry, automation, telecommunication. Many efforts are done to improve the manufacturing technologies for obtaining the high performance PTC thermistors. The paper deals with the obtaining semiconductive ceramic based on barium titanate doped with niobium, with different techniques of structure control during the manufacturing to obtain optimal parameters. Different methods for obtaining the thermistors electric contacts are analyzed, tested and optimized. The ohmic metal-semiconductor contacts, with a good mechanical resistance, stable in time, which do not oxidize at low and high temperatures, are obtained using the different techniques: cathodic sputtering, screen printing, manually depositing by rubbing of an alloy. The measurements of electric resistance versus temperature for the representative samples are presented and some conclusions regarding the advantages of used techniques are underlined.