PROPERTY STUDIES OF PLASMA SPRAYED TITANATES

Abstract

Use of plasma sprayed coatings is an important part of industrial production in many applications. This technique is mainly used for applications such as thermal barrier and wear resistant layers. Application of plasma sprayed coatings in the electronics industry lags behind its possibilities because there was lower attention to electrical properties of these coatings worldwide. This work provides new knowledge about the electrical and structural properties of titanates which are in the sintered state used as a dielectrics. Calcium titanate and barium-strontium titanate as promising materials in the form of the coating were selected as proper materials in this dissertation. Plasma deposited coatings exhibit di erent microstruc- ture and often phase and chemical composition when compared to the sintered material. Coatings were prepared by the conventional gas stabilized plasma torch as well as water stabilized plasma technology. Many experimental methods were used to bring a new knowledge about these materials. The electrical properties were studied by frequency dependence of relative permittivity and loss factor or by measuring electrical breakdown strength, electrical resistivity and determination of band gap. The morphology of coatings was studied by both light and electron microscopy. Phase composition was characterized by X- ray di raction analysis including high temperature in-situ experiments. Raman spectroscopy and X-ray photoelectron spectroscopy were used to analyze the chemical composition. The mechanical properties were analyzed by microhardness and elastic modulus measurements. All these measurements and discus- sion of the results bring a new knowledge about plasma deposited titanates and thereby contribute to greater potential application of these materials in the electronics industry.