The Impact of Al³⁺ ion substitution on microwave absorption of hexaferrite compound Ba_0.6Sr_0.4Fe_12−xAl_xO₁₉ (x = 0.25, 0.50, 0.75, and 1.00)

This paper discusses the impact of Al³⁺ ion substitution on Fe³⁺ ions in the hexaferrite compound Ba_0.6Sr_0.4Fe_12−xAl_xO₁₉ on the reflection loss value and bandwidth in absorbing microwaves. Hexaferrite Ba_0.6Sr_0.4Fe_12−xAl_xO₁₉ (x = 0.25, 0.50, 0.75, and 1.00) was synthesized by high-energy ball milling (HEBM) for forty hours, followed by sintering at 1000 °C in the air for five hours. Then, the crystal structure, formed phase, surface morphology, magnetization, and ability to absorb microwaves in the X-band region were successively characterized. All samples (x = 0.25, 0.50, 0.75, and 1.00) had a single phase with a hexagonal crystal structure. The particle size remained heterogeneous, ranging from 200 to 300 nm, with a platelet-like shape. The maximum amount of magnetic energy that could be absorbed by the material (M_s) increases from x = 0.25 to 0.75 and then decreases slightly for x = 1.00. The maximum value of reflection loss (RL_max) decreases as x increases. For x = 0.25, RL_max is − 16.17 dB (f = 11.06 GHz) with a bandwidth of 3.56 GHz, whereas for x = 1.0, RL_max is −13.94 dB (f = 11.14 GHz) with a bandwidth of 1.68 GHz.