Heat-treatment effect on Z-type hexaferrite for RF device application

Abstract

The Z-type hexaferrite Ba_1.5Sr_1.5Co₂Fe₂₄O₄₁ was synthesized by using a solid state reaction method under various heat-treatment conditions. The crystal structure and magnetic properties at high frequency were characterized by on x-ray diffractometer, network analyzer, vibrating sample magnetometer, and Mössbauer spectrometer. The Ba_1.5Sr_1.5Co₂Fe₂₄O₄₁ samples prepared by using the step calcination (SC12) process showed the considerably improved permeability and magnetic loss compared to those prepared by using the other processes due to the complete formation of Z-type phase from the calcination. When Co₂Z sample prepared by using SC12 process was sintered at 1125 °C and cooled at a slow rate, the value of magnetic loss tanδ _μ remained below 0.1 up to 750 MHz, and at 750 MHz, the values of permeability, permittivity, and dielectric loss were μ′ = 7.9, ε′ = 10.9, and tanδ _ε = 0.01, respectively.