Considerable demands of modern technology for new materials with specific properties have raised many possibilities for the investigation of glasses and glass-ceramics. Preparation of new glass and glass-ceramics with characteristic properties and the investigation of relationships among compositions, structure, electrical and thermal properties are important for understanding the mechanisms involved in these materials. The objectives of the proposed research is to prepare novel multi-compositional phosphate-based glasses, determine the correlation among both types of charge carriers, ions and electrons, present in proposed systems. In order to accomplish this, the proposed project is divided into three main interrelated steps. 1. First part will be focused on the conduction mechanisms in phosphate-based glasses that exhibit mixed electronic-ionic conduction. 2. Second part includes study of the influence of the mixed glass former effect on electrical processes in phosphate-based glasses. 3. Third part involves study of the influence of controlled crystallization on electrical transport in selected model glasses from steps 1 and 2. The formation of crystalline grains in a glass matrix can substantially change electrical conductivity and dielectric properties of glass. The idea is to perform systematic studies for understanding the charge transport (ion and electron) dynamics in glasses and glass-ceramics with different crystallinity (from fully amorphous to fully crystallized). The main aim is to determine the universality of the mixed electronic-ionic and mixed glass former effects in proposed glasses. The interactions between glass formers and modifiers, the formation of bonds among them are essential factors that influence the electrical properties of glasses. Beyond the connection to the central theme of conduction mechanism important from academic point of view, the selected systems are all associated with their multiple applications as advanced electrolytes.