Tuning Metal-Insulator Transition in Rare-Earth Nickelates for Zero Differential Thermal Emitter Applications

Zero differential thermal emitters (ZDTEs) are vital in applications requiring stable thermal radiation in dynamic thermal environments. One approach to create a ZDTE surface is to control its emittance by utilizing phase transitions in carefully chosen materials. The most studied material for this purpose is vanadium oxide. Here, we will show a family of alternative materials to achieve the same goal: rare-earth perovskite nickelates. They present a rich phase diagram with a large number of physical properties, one of which is their sharp metal-insulator transition, MIT. The MIT temperature (T_MIT) can be easily adjusted by changing or mixing the rare-earth cations. Associated with the MIT, a rapid change in optical properties is observed: as conductivity increases, emittance decreases. We will present our results on nickelate thin films grown by Pulsed Laser Deposition (PLD), demonstrating how to shift their T_MIT to room temperature by using a combination of Sm and Nd cations. Moreover, we will show that it is possible to further modulate the T_MIT by changing the applied strain. The optical properties of the films will be shown, linking the decrease in emittance to the resistivity and the applied strain. Our findings could pave the way for engineering future ZDTE surfaces.