Ni-Zn spinel type ferrites are interesting materials due to their both magnetic and semiconductor properties. These materials are widely used and exploited already from the 50ties of the last century. Nowadays, the use of the ferrite materials grows and, continuing miniaturization trend in electrical engineering, there is a need to develop synthesis methods and to do characterization of the ferrite nanomaterials. Moreover, the variety of ferrite applications grows. For example, spinel ferrites due to their transition metal semiconductor properties in the last decade are found to be used as gas sensor materials. With an increasing need in gas detection for environmental monitoring purposes, such as industrial process control, the use of gas sensors increases. First, it should be known, that as gas sensors can be used materials with high specific surface area – nanomaterials. Also, the semiconductor gas sensors should have fast response behaviour, low response to environmental humidity, high selectivity and long term stability. A material which has all mentioned properties does not exist; thus, searching for new materials or modifying the possibilities of the existing materials is still a topical problem. For example, SnO2 as a gas sensor material is used already from 1962, but in the field of gas sensors, investigations regarding its modification possibilities are still continuing. The optimisation ways of the spinel type ferrite gas sensor materials are in the starting position. By analysing the literature on the subject, it can be concluded that there is no attention paid to the influence of the charge carrier (point defect) concentration on ferrite gas sensitivity. It is known that electric conductivity is directly connected with metal oxide semiconductor gas sensor sensitivity; thus, in the current PhD work attention first and foremost is paid to the investigation of the electrical properties of Ni-Zn ferrite nanomaterials. In accordance with the above mentioned the main attention is paid to the synthesis of Ni-Zn ferrite nanomaterials, as well as to the investigation of electric, dielectric and gas sensing properties. In general, the work can be divided into five parts. In the first part attention is paid to the Ni-Zn ferrite synthesis by sol-gel auto combustion (SGAC), in the second part - to the investigation of the influence of composition and stoichiometry on the physical properties of nanostructured Ni-Zn ferrites. The third part is devoted to the influence of the processing temperature on the physical properties of Ni-Zn ferrites. The fourth part is dedicated to the synthesis and properties of nanostructured Ni-Zn ferrite thin films and the last, fifth part, is meant for the investigation of Ni-Zn ferrite gas sensitivity.