Search

B2O3 was used to reduce the sintering temperature of steatite (named MSB) dielectric ceramics. Electrical properties of this composition have been studied using impedance spectroscopic method to get better understanding of the electrical conduction, dielectric relaxation mechanism, and microstructure-electrical properties relationship of the materials as a function of temperature and frequency. These samples were prepared by a solid-state reaction technique and their single phase formation was confirmed by the X-ray diffraction technique. Dielectric and complex impedance spectroscopic studies were carried out in a wide frequency (102-106 Hz) and temperature (30-500°C) range. The dielectric constants decrease with increasing frequency for each sample, and then stabilize at frequencies lower than 100 kHz. The dielectric constant increases with the addition of B2O3. The nature of frequency dependence of ac conductivity of MSB follows the Jonscher power law and calculated DC conductivity follows Arrhinius behavior. The Nyquist plot (Z″ vs Z') revealed the presence only of the grain boundary effect from 350°C onwards. The occurrence of single arc in the complex modulus spectrum of MSB compositions confirms the single-phase characteristics, and also confirms the presence of non-Debye type of multiple relaxations in the material.

To study the effect of B2O3 and P2O5 on fluorosilicic mica glass-ceramic sintering process, six sets of K2O-MgO-SiO2-F glasses were prepared by using B2O3 and P2O5 as sintering aid, respectively. Green bodies of the glass powder were formed by gel casting and sintered at 800, 850, 900, 950, 1000oC for 6 hours, resectively. The sintering and crystallization behavior were studied by thermal shrinkage , X-ray diffraction and SEM. The results showed that the shrinkage rate of the glass with 2wt% B2O3 and P2O5 was highest, while the rate of the glass with 5wt% P2O5 was lowest. An additional crystal other than fluorosilicic mica was precipitated in the glass ceramics generated by sintering of glass powder. The present results confirmed that the glass powder of pure K2O-MgO-SiO2-Fsystem had poor sinterability, while glass powder with minor addition of P2O5 and/or B2O3 showed good sinterability. This result was also verified by SEM.