The dielectric behavior and efficient microwave absorption of doped nanoscale LaMnO3 at elevated temperature

LaMnO 3 perovskite has great potential in microwave absorption at high temperature due to its complex doping effect and super stability. The current research mainly focuses on the doping ratio regulation, while the mechanism of doping effect at high temperature is still lack of sufficient investigation. In this work, La 1− x Sr x Mn 1− y Fe y O 3 (LaMnO 3 , La 0.7 Sr 0.3 MnO 3 , and La 0.7 Sr 0.3 Mn 0.8 Fe 0.2 O 3 ) nanostructures with different doping sites were successfully prepared by the solid phase reaction method. Then, the high temperature dielectric test samples were obtained by mixing with cordierite (2MgO·2Al 2 O 3 ·5SiO 2 (MAS)). The results showed that the temperature dependence of Mn ion spin state had a significant impact on the high temperature dielectric behavior of La 1− x Sr x Mn 1− y Fe y O 3 . Particularly, when the thickness is only 1.9 mm, La 0.7 Sr 0.3 Mn 0.8 Fe 0.2 O 3 /MAS can achieve the widest bandwidth of 4.2 GHz covered the entire X-band (8.2–12.4 GHz) and a minimum reflection loss (RL) value of −17.99 dB at 500 °C. In order to improve the operating temperature of La 0.7 Sr 0.3 Mn 0.8 Fe 0.2 O 3 /MAS, a cellular array structure was designed by using computer simulation technology (CST) software to introduce magnetic loss. When the outer length of the hexagon is 1 mm and the coating thickness is 1.9 mm, the widest bandwidth covers the X-band and the minimum RL value is −15.35 dB at 800 °C. Therefore, La 0.7 Sr 0.3 Mn 0.8 Fe 0.2 O 3 has a great prospect as an efficient high temperature microwave absorber.