Structural and dielectric properties of (100-x)B2O3-(x/2)Bi2O3-(x/2) Fe2O3 glasses and glass-ceramic containing BiFeO3 phase

Glasses of the compositions (100 - x)B2O3-(x / 2)Bi2O3-(x / 2)Fe2O3 with x = 50, 60 and 70 (in mol%) were prepared. The glassy phase of the samples was established by X-ray diffraction (XRD) and Differential thermal analysis (DTA) studies. The formation of the BiFeO3 phase inside the glass matrix (glass-ceramic) by the heat treatment of the sample at x = 60 was identified by XRD, DTA and Fourier transform infrared (FTIR) studies. FTIR results revealed that the glass samples are composed of BO3, BO4, BiO3, BiO6, FeO4 and FeO6 basic structural units. The trends of the glass transition temperature (T-g), density (rho), molar volume (V-m), oxygen packing fraction (OPD) and theoretical optical basicity (A(th)) were discussed in terms of the structural modifications that take place in the glass matrix. The variation of the dielectric constant (epsilon(r)), dielectric loss (tan delta) and the ac conductivity of the glass samples cannot be explained on the basis of the distance between iron ions (R-i) only but on the space charge polarization. The dielectric properties of the glass-ceramic were affected by the presence of BiFeO3 phase inside the glass matrix.