Hexagonal M type SrFe12O19 (SrM) ferrites were synthesized by the hydrothermal method, and the effects of molar ratio of (RO/N), the atomic ratio of Fe/Sr (RF/S) and sintering on the phase composition and magnetic properties of as-synthesized specimens are studied. It is found that the RO/N and RF/S in starting materials affect the phase composition and magnetic properties greatly. Fe2O3 is found as impurity in some specimens, while in all as-synthesized specimens, SrCO3 forms inevitably during the synthesis process. After sintering at 1100 °C, the perovskite type SrFeO3−x ferrite forms as the product of SrCO3 and Fe2O3 at high temperature, and the specimens exhibit the Perminvar magnetic hysteresis loops which show two-phase magnetic behaviors. However, when sintered at 1200 °C, SrFeO3−x further reacts with Fe2O3 to produce SrFe12O19, and the specimens with RF/S=8, 9 and 10 exhibit the single-phase hexagonal structure and magnetic behavior. It is also found that the saturation magnetization and coercivity are both enhanced after sintering at high temperatures due to the elimination of impurities.Highlights► SrM ferrites are hydrothermally synthesized under a pressure less than 1 MPa. ► SrCO3 forms inevitably in the hydrothermal process. ► Perovskite SrFeO3−x forms in specimens after sintering at 1100 °C. ► Pure SrM ferrite forms after sintering at 1200 °C. ► The magnetic properties are enhanced after sintering at high temperatures.
Hexagonal M type SrFe12O19 (SrM) ferrites were synthesized by the hydrothermal method, and the effects of molar ratio of (RO/N), the atomic ratio of Fe/Sr (RF/S) and sintering on the phase composition and magnetic properties of as-synthesized specimens are studied. It is found that the RO/N and RF/S in starting materials affect the phase composition and magnetic properties greatly. Fe2O3 is found as impurity in some specimens, while in all as-synthesized specimens, SrCO3 forms inevitably during the synthesis process. After sintering at 1100 °C, the perovskite type SrFeO3−x ferrite forms as the product of SrCO3 and Fe2O3 at high temperature, and the specimens exhibit the Perminvar magnetic hysteresis loops which show two-phase magnetic behaviors. However, when sintered at 1200 °C, SrFeO3−x further reacts with Fe2O3 to produce SrFe12O19, and the specimens with RF/S=8, 9 and 10 exhibit the single-phase hexagonal structure and magnetic behavior. It is also found that the saturation magnetization and coercivity are both enhanced after sintering at high temperatures due to the elimination of impurities.<br><br>ไฮไลท์<br>►แม่เหล็ก SRM มีการสังเคราะห์ hydrothermally ภายใต้ความกดดันน้อยกว่า 1 MPa ►รูปแบบ SrCO3 หลีกเลี่ยงไม่ได้ในกระบวนการ hydrothermal ► perovskite SrFeO3-x รูปแบบในตัวอย่างหลังจากการเผาที่ 1100 องศาเซลเซียส ►รูปแบบ SRM เฟอร์ไรท์เพียวหลังจากเผาที่ 1200 องศาเซลเซียส ►คุณสมบัติแม่เหล็กจะเพิ่มขึ้นหลังจากการเผาที่อุณหภูมิสูง
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