Influence of Nanocrystallization on the Electronic Conductivity of Zinc Iron Phosphate Glass

The effect of nanocrystallization on the electronic conductivity of 10ZnO-30Fe2O3-60P2O5 glass has been investigated using differential thermal analysis (DTA), XRD, Raman, and impedance spectroscopy. the structural evolution of glass during heat treatment at various temperatures for 24 h is characterized by the dendrite-like phase separation in the early stage of nanocrystallization, which produces isolated agglomerates of Fe3(P2O7)2 crystallites. Formation of randomly dispersed agglomerates of Fe3(P2O7)2 crystalline grains results in a decrease of Fe2+-Fe3+ pairs concentration in a predominant glassy phase causing a minimum in electrical conductivity at 8.82 × 10−13 (Ω·cm)−1. with increasing the heating temperature up to the first crystallization temperature, TC1, the conductivity increases and simultaneously the activation energy decreases as the nanocrystallization is more pronounced in these samples. Heat treatment at higher temperature near TC2 exhibits the highest electrical conductivity, 2.97 × 10−10 (Ω·cm)−1. Upon heating at TC2, the sample undergoes further nanocrystallization causing slight decrease in the electrical conductivity. This effect can be understood as a result of the partial blocking of conduction pathways for the polarons along the interfaces between polycrystalline grains and through poorly conductive crystallites. the conductivity of this thermally treated glass is independent of the ZnO content and arises from the polaron hopping between Fe2+ and Fe3+ ions suggesting electronic conduction