Grain-Size Effects on the Structural and Electrical Properties of Iron–Based Nano-Crystalline Glass-Ceramic

Abstract

35Fe2O3-20Bi2O3-45P2O5 glass was produced by conventional melt-quenching method. The structural of the present glass and its heat treated samples were studied by using scanning electron micrographs (SEM), X- ray diffraction (XRD) and differential thermal analysis (DTA) techniques. The nano-crystalline glass ceramic obtained by heat treated at TCI for 2h exhibits giant improvement of electrical conductivity up to about five orders of magnitude. The conductivity enhancement was attributed to interfacial regions surrounding crystalline grains. However, the glass heat treated at TcI for 4,8 and 24 h the microstructure changes considerably. When grains are large and amorphous phase disappears, then these interfacial regions also vanish and conductivity of the material considerably decreases. The enhancement of electrical conductivity results during nanocrystallization were discussed in terms of a model proposed in this paper and based on a “core-shell” concept.