Chemical-pressure-enhanced Jahn-Teller distortion in (Cu, Cr, Mn)3O4 spinel for high-temperature broadband emissivity

Chemical pressure engineering of Jahn-Teller distortion enables broadband high emissivity. • A quantitative Jahn-Teller distortion index ( Q OJT ) is established to correlate structure with emissivity. • Ca 2+ doping (Cu, Cr, Mn) 3 O 4 spinel achieves an emissivity of 0.947 across the 0.4–25 μm range. • Exceptional thermal stability is demonstrated with less than 1.4% degradation at 1673 K. • An 11% enhancement in heating rate is achieved in practical radiative heating tests. Infrared radiation materials with broadband emissivity and high thermal stability are highly desirable for energy saving and thermal management applications. However, achieving high emissivity across the visible to mid-infrared range (0.4–25.0 μm) remains challenging due to the discontinuous absorption mechanisms in ceramics. Herein, a strategy based on promoting Jahn-Teller (JT) distortion is proposed to enhance the broadband emissivity of (Cu, Cr, Mn) 3 O 4 spinel. Substituting Cu 2+ with alkaline-earth ions (Mg 2+ , Ca 2+ , Sr 2+ ) introduces tunable chemical pressure, which modifies the local electric field and valence state distribution, thereby regulating the JT structural evolution. An octahedral JT structural descriptor ( Q OJT ) is developed to quantitatively compare JT structural evolution among different compositions. The Q OJT values show a positive correlation with broadband emissivity. The optimized JT structural evolution simultaneously enhances electronic transition, carrier and lattice vibration absorption, enabling synergistic regulation of broadband emissivity across the entire 0.4–25.0 μm spectral range. Among the investigated compositions, Ca 2+ -doped (Cu, Cr, Mn) 3 O 4 exhibits a broadband emissivity of 0.947 and maintains excellent stability under a simulated hypersonic environment at 1673 K. In radiative heating test, it achieves a heating rate approximately 11% higher than that of Al 2 O 3 . These findings demonstrate that chemical pressure provides an effective strategy for regulating JT structural evolution and designing broadband thermal radiation ceramics for high temperature applications. Download: Download high-res image (225KB) Download: Download full-size image Chemical-pressure-tuned Jahn-Teller distortion in (Cu, Cr, Mn) 3 O 4 spinel enables broadband high emissivity (0.947, 0.4–25.0 μm) and exceptional thermal stability up to 1673 K. A quantitative octahedral Jahn-Teller distortion index ( Q OJT ) correlates directly with emissivity performance. The optimized material achieves a 11% acceleration in heating rate, demonstrating its potential for high-temperature radiative transfer and thermal management applications.