Morphological regulation on barium titanate perovskite particles for broadening microwave absorption in GHz and THz range

Abstract

This study presents a two-step hydrothermal synthesis of barium titanate (BTO) crystals with four distinct morphologies of spherical (BTO-0), rod-like (BTO-1), platelet-like (BTO-2), and blocky (BTO-3). Utilizing TiO₂/NaOH-derived sodium titanate (NTO) precursors and Ba (OH)₂·8H₂O-mediated pH/Ba–Ti ratio control, we systematically correlated morphological evolution with MA performance. Notably, BTO-2 exhibits the highest specific surface area (246.280 m² g⁻¹) among the series, which facilitates the creation of abundant oxygen vacancies and enhances polarization loss. Furthermore, vibrating sample magnetometry (VSM) confirms its distinctive soft ferromagnetic behavior (saturation magnetization of 0.01 emu g⁻¹), contrasting with the diamagnetic responses observed in BTO-0, BTO-1, and BTO-3. Most critically, BTO-2 demonstrates record-breaking electromagnetic wave absorption performance, a minimum reflection loss (RL_min) of −34.73 dB and an effective absorption bandwidth (EAB) of 7.18 GHz. Furthermore, it exhibits a maximum reflection loss (RL) of 39.45 dB with an average absorption coefficient of 0.85 in the 0.09–2.06 THz frequency range at a minimal thickness of 600 µm. The unique dual-peak absorption mechanism arises from localized spin rearrangement and electromagnetic coupling, induced by interlayer electron repulsion and oxygen-vacancy-mediated quantum tunneling. The stacked platelet morphology creates confined electron transport channels, amplifying eddy current losses while suppressing skin effects.