Thermal instability and microstructure of strontium M-type hexaferrite nanoparticles synthesized by citrate approach

Abstract

The dried gel of SrFe₁₂O₁₉, prepared by citrate approach, was investigated by means of infrared spectroscopy (IR), thermograimetric analysis (TG), differential scanning calorinetry (DSC), X-ray diffraction (XRD) techniques, energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The thermal instability and the thermal decomposition of low-temperature strontium M-type hexaferrite crystallized at about 600°C were confirmed for the first time by XRD method. The decomposition of the low-temperature strontium M-type hexaferrite took place at about 688.6°C determined by DSC investigation. The low-temperature strontium M-type hexaferrite nanoparticles were decomposed into SrFeO_2.5 with an orthorthombic cell and Fe₂O₃ with a tetragonal cell as well as possible α-Fe₂O₃. The agglomerated particles with sizes less than 200 nm obtained at 800°C were plesiomorphous to strontium M-type hexaferrite. The thermally stable strontium M-type hexaferrite nanoparticles with size less than 100 nm could take place at 900°C. Up to 1000°C, the phase transformation to form strontium M-type hexaferrite was ended, the calcinations with the sizes more than 1 μm were composed of α-Fe₂O₃ and strontium M-type hexaferrite. The method of distinguishing γ-Fe₂O₃ with a spinel structure from Fe₂O₃ with tetragonal cells by using powder XRD method was proposed. Fe₂O₃ with tetragonal cells to be crystallized before the crystallization of thermally stable strontium M-type hexaferrite was confirmed for the first time. The reason why α-Fe₂O₃ as an additional phase appears in the calcinations is the cationic vacancy of strontium M-type hexaferrite,SrFe _l2-x▭_x O ₁₉(0⩽x⩽0.5). 3

Keywords

strontium M-type hexaferrite SrFe₁₂O₁₉ / thermal decomposition of low-temperature SrFe₁₂O₁₉ nanoparticles / microstructure evolution

References

[1] Shengping Ruan, Baokun Xu, Hui Suo, . Microwave Absorptive Behavior of ZnCo Substituted W-type Ba Hexaferrite Nanocrystalline Composite Material [J]. J. Magn. Magn. Mater., 2000, 212: 175-177.

[2] Sugimoto S, Kondo S, Okayama K, . M-type Hexaferrite Composite as a Microwave Absorber with Wide Bandwidth in the GHz Range[J]. IEEE Trans. Magn., 1999, 35(5): 3154-156.

[3] Han-Shin Cho, Sung-Soo Kim. M-hexaferrites with Plannar Magnetic Anisotropy and Their Application to High-frequency Microwave Absorbers[J]. IEEE Trans. Magn., 1999, 35(5): 3151-3153.

[4] Yongxiang Zhang, Ronglin Ding, Tao Li, Jiyang Cui, Wei Zhu. Study on Hexagonal Polycrystalline Ferrite Material with Electron-wave Absorbing[J]. J. of Chin. Ceram. Soc., 1998, 26(3): 275-280.

[5] Gang Xiong, Xujie Yang, Xiaohui Wang, Lude Lu, Xin Wang. Synthesis and Characterization of X-type Barium Ferrite Nanocrystals[J]. Chem. J. of Chin. Univ., 1998, 19(9): 1467-1470.

[6] Zongyu Zheng, Zhiguo Liu. Synthesis of Single Phase Barium Hexaferrite Powders by Coprecipitate Assistant-melt Technique[J]. J. of Magn. Mater. Devic., 1986, 1: 27-33.

[7] Lin C H, Shih Z W, Chiu T S, . Hydrothermal Processing to Produce Magnetic Particulates [J]. IEEE Trans. Magn., 1990, 36(1): 15-17.

[8] Gornert P, Sinn E, Schuppel W, . Structure and Magnetic Properties of BaFe_2−2xCo_xFe₁₆O₂₇ Powders Prepared by the Glass Crystallization Method[J]. IEEE Trans. Magn., 1990, 26(1): 12-14.

[9] Sürig C, Hempel K A, Bonnenberg D. Formation and Microwave Absorption of Barium and Strontium Ferrite Prepared by Sol-sel Technique [J]. Appl. Phys. Lett., 1993, 63(20): 2836-2838.

[10] Hongguo Zhang, Ji Zhou, Zhenxing Yue, lin Zhuo, Zhilun Gui, Longtu Li. Preparation of Low-temperature Sintering Z-type Hexaferrite by Gel Self-combustion Technique [J]. J. of Funct. Mater., 2000, 31: 36-38.

[11] González-Carreño T, Morales M P, Sema C J. Barium Ferrite Nanoparticles Prepared Directly by Aerosol Pyrolysis[J]. Materials Letters, 2000, 43: 97-101.

[12] Shafi k V P M, Gedanken A. Sonochemical Approach to the Preparation of Barium Hexaferrite Nanoparticles[J]. Nano Structured Materials, 1999, 12: 29-34.

[13] Jiye Fang, John Wang, Leong-Ming Gan, Ser-Choon Ng, Jun Ding, Xiangyuan Liu. Fine Strontium Ferrite Powders from an Ethanol-based Microemulsion[J]. Journal of America Ceramic Society, 2000, 83(5): 1049-1055.

[14] Zhao Wenyu, Zhang Qingjie, Guan Jianguo. Factors of Impacting the Coprecipitation Process for Synthesizing Coti-substituted Barium M-type Hexaferrite Ultrafine Powder[J].J. of Wuhan University of Technology—Materials Science Edition, 2004(in press)

[15] Yu H F, Huang K C. Preparation and Characterization of Ester-derived BaFe₁₂O₁₉ Powder[J]. J. of Mater. Res., 2002, 17(1): 199-203.

[16] Milin Zhang, Ming Zhou, Yanfeng Xin, Xiaoyan Jing. Synthesis of Ultrafine Powder SrFe₁₂O₁₉ by Citrate Method[J]. J. of Chin. Ceram. Soc., 1996, 24(6): 685-688.

[17] Hongguo Zhang, Longtu Li, Ji Zhou, . Low-temperature Sintering, Densification, and Properties of Z-type Hexaferrite with Bi₂O₃ Additives[J]. J. of Am. Ceram. Soc., 2001, 84(14): 2889-2894.