Enhanced thermal stability and dielectric performance of δ-MnO2 by Ni2+ doping

Despite the wildly studies on MnO2, the poor stability limits its broad use. Here, Ni doping was used to enhance the stability of the MnO2. In this paper, Ni-doped δ-MnO2 was successfully synthesized through a hydrothermal method, and nickel ions exist as divalent Ni2+ in Ni-doped MnO2. Ni doping did not change the crystal phases but promote the growth of MnO2 microspheres and the dielectric loss factor increased by 80% after Ni doping. High temperature stability was investigated, the results showed the existence of Ni doping could block the solid-state diffusion at high temperature so that improve the thermal stability of MnO2, the phase, morphology and dielectric performance could keep consistent with the nonannealing samples. Meantime, first-principles calculation was used to uncover the stabilization mechanism on the microscopic scale.