| Summary: | 碩士 === 國防大學中正理工學院 === 應用化學研究所 === 95 === In this study, nanopowders of SrFe12O19 and SrTiO3 were tried to prepare by a combustion synthesis method using metallic nitrates and glycine as reactants. By adjusting the glycine-to-nitrates ratio, the oxygen balance (OB) values of the reactant mixtures can be varied in which the combustion phenomena is altered and thereby the as-synthesized products with different characteristics are obtained. Development of crystalline phases in the as-synthesized powders after heat-treatments at various temperatures was monitored by X-ray diffraction. Nearly single-phased SrFe12O19 could be obtained after calcination of the as-synthesized Sr-ferrite powder at a temperature ≧ 900℃ for 1 h, whereas single-phased SrTiO3 could be formed directly after the combustion reaction without calcination at the same OB value. Associated with he experimental results, possible reasons were proposed to explain why the formation of perovkskite-structured SrTiO3 was more readily than that of M-type SrFe12O19 belonging to hexagonal crystal system.
On the other hand, the hard-magnet of M-type strontium ferrite (SrFe12O19, abbreviated as Sr-M) incorporated with the high-dielectric material of strontium tiatanate (SrTiO3, shortened to STO) in the range of 0.00-0.15 molar ratio was prepared simultaneously in one step by using the combustion method performed in our previous study. The effects of SrTiO3 additive on the relative complex permittivity ( ), permeability ( ) and the behavior of microwave absorption in the frequency range of 1 MHz-1.8 GHz have been investigated. Judging from the XRD analysis, it is revealed that the products as-synthesized contained the by-products of SrCO3 and Fe2O3 in addition to the excepted phases of M-Sr and STO. However, the calcined and even the sintered products were the simple composites composed of M-Sr and STO. Adding more STO to M-Sr was demonstrated not only to improve the but also to modify the . Besides, it was found that the reflection band became broader and shifted to lower frequency with increasing STO content, but the absorption efficiency [i.e., the minimum point of dB attained] was degraded gradually.
Keywords:Combustion synthesis; Oxygen balance; Nitrates; Glycine; SrFe12O19; SrTiO3; Complex permittivity; Complex permeability
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