Influence of the preparation conditions and thermal treatment on the structure of the B2O3-BaO-Fe2O3 system

The structure of xFe(2)O(3) (.) (100 - x)[3B(2)O(3)-BaO] system with 0 <= x <= 50 mol% was studied by DTA, X-ray diffraction, density, optical microscopy and EPR measurements in vitreous and partial crystallized state, the samples being obtained by under cooling method. The data obtained show that, by melting the samples at T-e = 1200 C or T-e = 1250 degrees C, glasses for x <= 35 mol% were obtained, and the forming of crystalline microprecipitates of Fe2O3 in the sample with x = 50 mol%. It was also established that the thermal treatment at 565 degrees C without and in the presence of magnetic field of 0.7 T is influencing the forming and the development of the Fe2O3 microcrystals in samples with x >= 35 mol%. The samples melted at T-c = 1200 degrees C and T-c = 1250 degrees C were studied by magnetic susceptibility measurements which evidenced similar results with those obtained by EPR. Also, the magnetic measurements show that for the thermal untreated samples the iron ions participate at superexchange interactions for x >= 5 mol% and for x >= 10 mol%, respectively.