Effect of Na₂O and SrO Addition on Magnetic Properties of Anisotropic SrZn₂ System W-Type Hexagonal Ferrite Magnets.

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  This experiment was carried out to investigate the effect of Na₂O and SrO additives on the magnetic and physical properties of SrZn₂-W type hexagonal ferrite. The specimens were prepared by the conventional manufacturing methods without the atmosphere control. It was found that the magnetic properties of SrO • 2ZnO8Fe₂O₃ were considerably improved on adding 1.33wt% Na₂O and 0.67wt% SrO after semisintering treatment. The optimum condition of making magnet with suitable properties are as follows : chemical analysis composition: Sr²⁺_0.953Zn²⁺_1.595Na⁺_0.271Fe²⁺_0.080Fe³⁺_16.157O₂₇ ; semisintering condition : 1300°C x 1h in air ; sintering condition : 1250°C x 0.5h in air. The magnetic properties are : J_m = 0.415 T, J_r = 0.375 T, H_cJ = 123.4 kA/m, H_cB = 118.6 kA/m, (BH)_max = 22.8 kJ/m³, T_c = 361°C, H_A = 1084 kA/m, K_A = 2.25 x 10⁵J/m³ and n_B = 33.8μB. The magnetic properties of this compound powder heated at 1100°C after milling are σ₅ = 82.9x10^-6Wb·m/kg and H_cJ = 199 kA/m, and they are useful as the bonded magnet material.