Microwave absorption of M-type hexaferrite Ba _1-x Ca _x Fe ₁₂ O ₁₉ (x ≤ 0.4) ceramics in 2.6–18 GHz

Ba _1-x Ca _x Fe ₁₂ O ₁₉ (x = 0.0, 0.1, 0.2, 0.3 and 0.4, BCFO) ceramics were prepared using high-temperature solid-state method and the effect of Ca ²⁺ substitution was investigated. The grain size of BCFO ceramics sintered at 1250 °C for 2 h increases from 1 µm to 5 µm as Ca ²⁺ added. The BCFO ceramics show a typical hard magnetic behavior with a maximum saturation magnetization (M _S ) of 51.8 emu g ⁻¹ at x = 0.2. The bandwidth of microwave reflection loss (RL) below − 10 dB (> 90.0% microwave absorption) is obtained in 7.60 − 9.8 GHz with the minimum RL − 30.8 dB at 8.5 GHz for x = 0.2 (thickness 2.0 mm), which makes Ba _0.8 Ca _0.2 Fe ₁₂ O ₁₉ ceramic a potential microwave absorption candidate.