Advantages of simultaneous use of IS/DS spectroscopy analysis in characterisation of transport properties of ceramics and chalcogenide glasses

Impedance spectroscopy (IS) is an established measurement method used for studying the electrical properties of a wide range of materials. The greatest advantage of this technique lies in collecting information about the materials’bulk phase (conductivity, dielectric permittivity) and their inner and outer interfaces simultaneously. Since it considers both the real and the imaginary part of the complex impedance, this approach is experimentally efficient and provides more information at the same time. Also, it enables characterization of the electrical behavior of materials for which differently coupled processes contribute to their overall response. Namely, the electrical response of heterogeneous systems varies and depends on charge transfer, diffusion and interface behaviors, which are difficult to analyze with traditional methods. In this sense, IS can be used to assess how charges are bounded or transferred by creation of an equivalent electric circuit model, whose elements consistently represent the electrical properties of the material. However, the low-frequency peak seen in several impedance spectra originatesfrom DC component of conductivity and therefore makes the real dielectric relaxation phenomena unable to be detected using this technique. Therefore, to conduct the comprehensive study about electrical inhomogeneity and carriers' behaviors in heterostructured materials combined impedance and dielectric spectroscopy analysis is frequently applied. The aim of DS study is to determine the time constants using peak maxima, either from frequency dependence at given temperature or from temperature variation at selected frequency. This paper presents relevant practical aspects of the interpretation and analysis of the electrical and dielectric behavior of three different classes of materials based on IS and DS modelling. The first class of materials refers to metal doped chalcogenide glasses (Bi-As-S system and Cu-As-Se system) for which IS/DS analysis was crucial in detection of different structural units and phases and characterisation of their contribution in impedance response. The analysis of electrical and dielectric parameters of nickel ferrite nano-powders doped with yttrium revealed contribution of both grains and grain boundary in conduction and relaxation processes. Effect of plasma treatment on self-cleaning features of acrylic paint/TiO2-coated surfaces for environmental pollutant removal was also investigated by the means of IS/DS and this analysis was significant for confirmation of contribution of oxygen vacancies.