La-Ca-Co-Zn 掺杂M型锶铁氧体的相变过程和磁性能研究

采用陶瓷法制备La-Ca-Co-Zn 掺杂的M型锶铁氧体Sr0.3La0.3Ca0.4Fe10.625Co0.225Zn0.1O19。使用高温X射线衍射仪、振动样品磁强计、热分析、和扫描电子显微镜等对Sr0.3La0.3Ca0.4Fe10.625Co0.225Zn0.1O19 在25°C 到1450°C的相变过程进行了分析，并且讨论了其磁性能。实验结果表明：La-Ca-Co-Zn 掺杂的M型六方铁氧体的形成主要分为两个部分，在大概700℃左右，SrCO3 和Fe2O3先反应生成中间相Sr3Fe2O7-d，然后Sr3Fe2O7-d再和剩下的Fe2O3反应生成M相，并且Sr3Fe2O7-d中的Fe离子化合价与温度有关；随着温度升高，La3+, Ca2+, Co2+ 和 Zn2+开始逐渐溶入中间相或者随后生成的M相中，且在M相中分布均匀；和高温射线衍射仪检测结果不同的是在700℃左右退火时，得到了钙钛矿相；在1200℃烧结，可以得到单一程度很高的M相，但有少量的第二相存在，第二相的存在有利于提高烧结致密度；当烧结温度为1380℃时，铁氧体开始分解；Sr0.3La0.3Ca0.4Fe10.625Co0.225Zn0.1O19 铁氧体粉末退磁曲线的矩形度要低于SrFeO12的退磁曲线矩形度。

The phase transformation and magnetic properties of La-Ca-Co-Zn doped M-type hexaferrites

The phase?transformation process form 25°C to 1450°C and magnetic properties of Sr0.3La0.3Ca0.4Fe10.625Co0.225Zn0.1O19 were investigated by means of high-temperature X-ray diffraction, thermal analysis, vibrating sample magnetometer and scanning electron microscopy. The formation of M-type hexagonal ferrites in air passes through two endothermal reactions. SrCO3 and partial Fe2O3 first generated the intermediate phase Sr3Fe2O7-d in around 700°C. And then Sr3Fe2O7-d and the remaining unreacted Fe2O3 generated SrFe12O19. Meanwhile, La3+, Ca2+, Co2+ and Zn2+ ions gradually dissolve in the intermediate phase or the late product M phase with the temperature increases. The perovskite was obtained when annealed at about 700°C, which may transform perovskite into Sr3Fe2O7-d during the cooling process. The average valence of Fe in Sr3Fe2O7-d was a function of temperature. A very high single degree of M phase and a small number of second phase were obtained at about 1200°C, and the cationic were evenly distributed in the crystal. The rectangularity of the demagnetizing curves of the LaCaCoZn-type substituted ferrite powder decreases compared to that of unsubstituted ferrite powder. The ferrite will be decomposed at about 1380°C.