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- Title
Kinetic study of crystallization titanium substituted barium hexaferrite in a glassy matrix of the system BaO-Fe<sub>2</sub>O<sub>3</sub>-TiO<sub>2</sub>-B<sub>2</sub>O<sub>3</sub>.
- Authors
QUIROZ, P.; HALBEDEL, B.
- Abstract
Differential thermal analysis (DSC), X-ray difrraction (XRD) and scanning electron microscopy (SEM) were used to study the crystallization behavior of the rapid cooled melt compositions (mole-%): 40 BaO + 33 B2O3 + (27 - x) Fe2O3) + x TiO2, with x = 0. 1.8, 3.6. 4.6 and 6.4 mole-% TiO2 for the production of electromagnetic absorber powders in the micro-wave range. After annealing of these cooled melts the crystalline phases BaB2O4, BaFe12 - x TixO19 and from melt substitutions of x >4.6 mole-% TiO2 a dielectric phase BaTi6O13 were determined by XRD. The Netzsch Thermokinetics® program was used in order to understand the phase transformations through the analysis of the kinetic parameters. Thereby the influence of temperature and heating rate was investigated. Overall activation energy of 311.74 ± 3 kJ mol-1 was obtained for the crystallization of barium hexaferrite with the ASTM E698® method. A slightly decreasing tendency in this energy was observed when the TiO2 content was increased, but it is not a significant variation despite the substitution. In addition, the Friedmann method was used to calculate the activation energy, because it is not constant throughout the crystallization process.
- Subjects
CRYSTALLIZATION; BARIUM ferrite; TITANIUM dioxide; DIFFERENTIAL thermal analysis; X-ray diffraction; SCANNING electron microscopy; PHASE transitions; ACTIVATION energy
- Publication
High Temperatures - High Pressures, 2013, Vol 42, Issue 4, p367
- ISSN
0018-1544
- Publication type
Article