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<p>Preparing insulating layers via interfacial solid-phase reactions is regarded as one of the most effective strategies for enhancing the magnetic performance of soft magnetic powder cores (SMPCs). However, mismatches in lattice structures between the insulating layer and the magnetic powder can cause cracking in the insulating layer, thereby compromising the stability and performance of SMPCs under operational conditions. This study presents a refined method for preparing insulating layers based on solid-phase reactions, utilizing the thermal decomposition of salt compounds in combination with powders of differing particle sizes: 99.4&#xa0;<i>μ</i>m (S1) and 8.9&#xa0;<i>μ</i>m (S2). Initially, the FeSiCr(S1+S2)/ZnSO<sub>4</sub> composite powder was synthesized through a hydrothermal method. Subsequently, FeSiCr(S1+S2)-based SMPCs with a SiO<sub>2</sub>@Cr<sub>2</sub>O<sub>3</sub>@ZnO (SCZ) composite insulating layer were successfully prepared by a combination of heat treatment and cold pressing. Then, we investigated the effect of varying powder ratios of different particle sizes on the microstructure and magnetic performances of FeSiCr(S1+S2)/SCZ SMPCs, and the results revealed that ZnSO<sub>4</sub> decomposes into solid-phase ZnO and gaseous SO<sub>2</sub> and O<sub>2</sub> during heat treatment. Among these, O<sub>2</sub> triggers the solid-phase reaction, causing non-magnetic Si and Cr atoms from the soft magnetic powder to migrate to the surface, leading to the formation of a composite insulating layer. The smaller FeSiCr(S2) powder fills gaps within the SMPCs and provides more sites for ZnSO<sub>4</sub> decomposition and insulating layer formation. This process allows for the uniform growth of an insulating layer on the surface of the magnetic powder, thereby reducing the lattice mismatch while simultaneously increasing the magnetic phase content. The optimal magnetic performance was achieved at a powder ratio of 60:40 wt% (S1:S2), with maximum saturation magnetization (172.9&#xa0;emu/g), magnetic permeability (31.3 at 10 mT, 500&#xa0;kHz) and low core loss (465.62&#xa0;kW/m<sup>3</sup> at 30 mT, 200&#xa0;kHz). These findings suggest that the optimized SMPCs are promising candidates for high-performance electromagnetic components.</p> Graphical Abstract <p></p>

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Mechanism of the Synergistic Control Strategy of Interfacial Reaction and Particle Size on the Microstructure and Magnetic Properties of FeSiCr Soft Magnetic Powder Cores

  • 期刊论文

  • 发表日期：

    2025年8月12日

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  • Jixiang Jia,
  • Haiwei Wang,
  • Guang Yang,
  • Zhihao Lu,
  • Rui Wang,
  • Zhaoyang Wu

摘要

Preparing insulating layers via interfacial solid-phase reactions is regarded as one of the most effective strategies for enhancing the magnetic performance of soft magnetic powder cores (SMPCs). However, mismatches in lattice structures between the insulating layer and the magnetic powder can cause cracking in the insulating layer, thereby compromising the stability and performance of SMPCs under operational conditions. This study presents a refined method for preparing insulating layers based on solid-phase reactions, utilizing the thermal decomposition of salt compounds in combination with powders of differing particle sizes: 99.4 μm (S1) and 8.9 μm (S2). Initially, the FeSiCr(S1+S2)/ZnSO4 composite powder was synthesized through a hydrothermal method. Subsequently, FeSiCr(S1+S2)-based SMPCs with a SiO2@Cr2O3@ZnO (SCZ) composite insulating layer were successfully prepared by a combination of heat treatment and cold pressing. Then, we investigated the effect of varying powder ratios of different particle sizes on the microstructure and magnetic performances of FeSiCr(S1+S2)/SCZ SMPCs, and the results revealed that ZnSO4 decomposes into solid-phase ZnO and gaseous SO2 and O2 during heat treatment. Among these, O2 triggers the solid-phase reaction, causing non-magnetic Si and Cr atoms from the soft magnetic powder to migrate to the surface, leading to the formation of a composite insulating layer. The smaller FeSiCr(S2) powder fills gaps within the SMPCs and provides more sites for ZnSO4 decomposition and insulating layer formation. This process allows for the uniform growth of an insulating layer on the surface of the magnetic powder, thereby reducing the lattice mismatch while simultaneously increasing the magnetic phase content. The optimal magnetic performance was achieved at a powder ratio of 60:40 wt% (S1:S2), with maximum saturation magnetization (172.9 emu/g), magnetic permeability (31.3 at 10 mT, 500 kHz) and low core loss (465.62 kW/m3 at 30 mT, 200 kHz). These findings suggest that the optimized SMPCs are promising candidates for high-performance electromagnetic components.

Graphical Abstract