Enhancing infrared emissivity and heat dissipation of BaFe12O19 via Sr substitution-induced lattice distortion

High-performance infrared (IR) radiative materials are important for energy conservation and electronic thermal management, yet effective strategies for simultaneously enhancing short- and long-wave IR emissivity remain limited. Herein, Sr-substituted barium hexaferrite (Ba 1− x Sr x Fe 12 O 19 , x = 0, 0.1, 0.3, and 0.5) powders were synthesized via chemical co-precipitation, and the effects of Sr substitution on the crystal structure, optical properties, and IR radiative performance were systematically investigated. Sr substitution at Ba sites induced lattice contraction and modified the local structural environment. The apparent optical bandgap decreased from 3.59 eV for BaFe 12 O 19 to 2.92 eV for Ba 0.7 Sr 0.3 Fe 12 O 19 . In the 2.5–5 μm band, Ba 0.7 Sr 0.3 Fe 12 O 19 exhibited an average emissivity of 0.62, corresponding to a 72.2% increase relative to BaFe 12 O 19 , which is associated with the reduced apparent optical bandgap and modified surface Fe/O chemical states detected by XPS. In the 8–14 μm band, the enhanced emissivity is mainly attributed to lattice-distortion-induced changes in the vibrational response, and Ba 0.7 Sr 0.3 Fe 12 O 19 exhibited an average emissivity of 0.90, representing a 3.4% increase over BaFe 12 O 19 . In the 2.5–15 μm range, its average emissivity reached 0.80, which is 63.3% higher than that of BaFe 12 O 19 . Furthermore, the Ba 0.7 Sr 0.3 Fe 12 O 19 /PVDF composite coating achieved a 6.5 °C reduction relative to a bare Cu plate and a 3.8 °C reduction relative to a pure PVDF coating. This work provides a low-cost and scalable strategy for improving the IR radiative performance of BaFe 12 O 19 -based materials through cation substitution and structural regulation, offering a promising route for thermal management in next-generation electronic devices.