基于sol-gel的钡铁氧体薄膜的制备及其性能研究

【作者】 唐浩；

【导师】 张万里；

【作者基本信息】 电子科技大学 ， 材料科学与工程， 2010， 硕士

【摘要】 M型六角钡铁氧体(BaM)由于具有稳定的化学性质、低损耗、高的磁晶各向异性以及旋磁特性,在磁记录和微波通信领域有着重要的应用。本文配置氢氧化铁、柠檬酸、EDTA三种溶胶体系,利用溶胶凝胶法制备钡铁氧体薄膜。主要研究溶胶体系中铁钡离子比、热处理温度和热处理时间等对钡铁氧体薄膜的织构、表面形貌和磁性能的影响。实验结果表明对于这三种体系的溶胶,均能得到具有C轴织构的BaM薄膜。铁、钡原子比为3、5、10.5、11和13.5的氢氧化铁溶胶体系均能够获得C轴取向的BaM薄膜。铁、钡原子比为10.5时BaM薄膜的C轴织构最好。在1000℃下,热处理3个小时后,获得了良好的C轴取向,薄膜晶粒的C轴垂直于膜面,且薄膜[110]方向与基片[100]方向平行。薄膜表面呈现片状晶粒与棒状晶粒混合的形貌。薄膜具有磁各向异性,面外方向比面内更容易磁化。增加热处理时间,面外饱和磁化强度增加,矫顽力先增加后减小。在1000℃下,热处理时间从1小时增加到4小时,饱和磁化强度从282.2 Gs增加到328.5 Gs,矫顽力从1459.85 Oe,增加到4019.6 Oe后减小为2900 Oe,最后减小到1567.3 Oe。随着膜厚的增加,薄膜C轴取向变差,而矫顽力增加,当膜厚增至1.05μm时,晶粒完全随机取向,剩磁比小于0.4,矫顽力接近4 kOe。柠檬酸体系的溶胶制备的钡铁氧体薄膜,薄膜表面以棒状晶粒为主。随柠檬酸含量的增加,薄膜C轴织构变差,棒状颗粒增多,导致面外矫顽力也相应增加。与氢氧化铁体系相比,获得好的C轴取向需要更高的热处理温度。实验结果表明在1100℃下,热处理3小时后,获得了比较好的织构。剩磁比约为0.55,矫顽力达到3.6 kOe。本实验的最佳溶胶体系为EDTA体系,其制备的BaM薄膜具有完美的C轴织构,薄膜的表面平整,具有明显的解理面。铁钡离子比为8和10.5均能形成高质量的薄膜。在1100℃,2个小时的热处理条件下,制备的钡铁氧体薄膜成规整的六角片状,具有非常强的单轴磁各向异性。面外方向,剩磁比达到0.75,矫顽力为3.4 kOe,面内方向,剩磁比为0.12,矫顽力约为1.1 kOe。更多还原

【Abstract】 M-type hexagonal barium ferrite (BaM) are widely applied in magnetic recording and microwave communication, due to its excellent chemical and mechanical stability, low loss, high magnetocrystalline anisotropy and gyromagnetic property. In this paper, Three different sols consisted of Fe(OH)3, citric acid and EDTA respectively were prepared and Sol-gel technology was used to fabricate BaM thin films. Effects of the ratio of Ba2+ to Fe3+, the type and amount of chelating agent, heat treatment condition on the morphology, the texture, and magnetic properties of BaM thin films were investigated. Our results show that the type of the sols has a significant influence on the morphology and performance of the BaM thin films. Thin films with c-axis texture can be obtained by the three sol systems.BaM thin films can be prepared by the Fe(OH)3 system with the ratio of Ba2+ to Fe3+ equal to 3、5、10.5、11 or 13.5 and the best texture can be acquired when the ratio is 10.5. BaM thin films with textured c-axis can be fabricated when the thin films were treated at 1000℃for 3 hours. The c-axis of the crystallites of the BaM thin films is normal to the sapphire (00l) substrates and the [110] direction of the film is parallel to the [100] direction of the substrate. The morphology of the film shows mixture of platelet-shaped and stick-shaped crystallites. The films present the magnetocrystalline anisotropy and easy magnetization direction is out-of-plane rather than in-plane. The saturation magnetization out-of-plane increases, while coercivity at first increases and then decreases with increase of annealing temperature. when the thin films were treated at 1000℃from 1 hour to 4 hours, the saturation magnetization can be improved from 282.2 Gs to 328.5 Gs ,however, the coercivity increase from 1459.85 Oe to 4019.6 Oe at first and then decrease to 2900 Oe, reach 1567.3 Oe at last. With the increase of the thickness, the preferential growth with c-axis perpendicular to the film plane was suppressed. The remanence ratio was less 0.4 and the coercivity was close to 4 kOe when the thickness of the thin films reached 1.05μm.The BaM thin films produced by adding citric acid preferred to nucleate with c-axis in plane. The morphology displayed that stick-shaped crystallites covered almost the whole surface of the thin films. The coercivity raised with the increase of the amount of citric acid. The preferential c-axis orientation growth needs higher annealing temperature, and well-textured thin films can be obtained at 1100℃for 3 hours.The prefer sol-system for the BaM thin film is EDTA system, The BaM thin films manufactured by EDTA system had clear facetted crystallites. The morphology of the crystallites indicated that crystallites were highly smooth. High-quality BaM thin films can be obtained when the atomic ratio of iron to barium is between 8 and 10.5. The thin films have regular hexagonal platelet-shaped crystallites and very strong perpendicular magnetic anisotropy after annealing for 2 hours at 1100℃. In the perpendicular direction, the remanence ratio and coercivity reach up to 0.75, 3.4 kOe respectively. The remanence ratio in-plane is about 0.12 and coercivity force is about 1.1 kOe.更多还原