Metal-like to insulator transition in Lu3Fe5O12

• Metal-like to insulator transition (MIT) is empirically proved for the first time.
• Variation in Nyquist and DC conductivity plots at 343 K which is attributed to MIT.
• MIT is discussed in terms of localized and delocalized egeg electrons.
• Impedance loss and dielectric permittivity plots also uphold the presence of MIT.

Polycrystalline Lu3Fe5O12, prepared using the solid state reaction method, has Fe in the mixed valence state as inferred from the X-ray photoelectron spectroscopy. A spectral change in the impedance plot at 343 K is attributed to metal-like to insulator transition (MIT), which is analyzed in terms of localized and delocalized egeg electrons. The change in the slope at 343 K in the DC conductivity plot also proves the MIT. The dependence of Z′Z′ on temperature and Z″Z″ on frequency clearly substantiates the presence of localized electrons up to 343 K and delocalized electrons above 343 K.