Pressure-induced suppression of Jahn-Teller distortions and enhanced electronic properties in high-entropy oxide (Mg0.2Ni0.2Co0.2Zn0.2Cu0.2)O

Jahn-Teller distortions are often observed in Cu-II-containing complex oxides resulting in remarkable changes of physical properties. Tuning the Jahn-Teller distortions with pressure has attracted considerable interest but is less studied in Cu-II-containing high-entropy oxides (HEOs). We found that pressure can suppress the structural distortions originating from the Jahn-Teller effect of CuO6 octahedra in the rock salt-type (Mg0.2Ni0.2Co0.2Zn0.2Cu0.2)O HEO and significantly modify its electronic properties. Synchrotron x-ray diffraction shows that the structural distortions arising from the Jahn-Teller effect of CuO6 octahedra are progressively suppressed, and the distorted structure evolves into a nearly ideal form under compression. Alternating current impedance and ultraviolet-visible absorption measurements reveal a dramatic resistance drop by more than three orders of magnitude and an obvious bandgap decrease in similar to 0.1 eV, respectively, accompanied by the pressure-induced suppression of structural distortions. Our study presents a promising route for tuning the structural distortions and the electronic structures of Cu-II-containing HEOs for optimizing materials functionalities. Published under an exclusive license by AIP Publishing.

Automated summary

The study reveals that pressure can suppress the structural distortions caused by the Jahn-Teller effect of CuO6 octahedra in Cu-II-containing high-entropy oxides (HEOs) and significantly modify their electronic properties. As pressure increases, the structural distortions are gradually suppressed and the electronic structure undergoes significant changes.