Stoichiometry-Controlled Coprecipitation Synthesis of Single-Phase Sr–Ni W-type Ferrite for Electromagnetic Wave Absorption

Optimized synthesis conditions for single-phase Sr–Ni W-type ferrite were established via a Na₂CO₃-assisted coprecipitation route. A NaOH-Na₂CO₃ mixed precipitant and calcination at 1250 °C produced single-phase W-type ferrite by preventing Sr loss during washing. The optimized W-type ferrite powders were incorporated into a thermoplastic polyurethane (TPU) matrix to fabricate thin, flexible composites. Electromagnetic characterization indicates dominant ferromagnetic resonance (FMR)-driven magnetic loss; transmission-line based reflection loss (RL) calculations predict a broad effective absorption bandwidth (EAB) of 9.3 GHz (40.9–50.2 GHz) at a thickness of 0.65 mm, with RLmin below –40 dB. These findings demonstrate that Na₂CO₃-mediated precursor control enables reproducible single-phase W-type ferrite and yields high-performance electromagnetic wave absorbers for mm-wave applications.