Colossal Dielectric Behavior and Dielectric Relaxation of (Li, Fe) Co-Doped ZnO Ceramics

The co-doped ceramics (Fe0.5Li0.5)(x)Zn1-xO (x=0.005, 0.01, 0.015) (abbreviated as FL-0.005, FL-0.01, and FL-0.015) as well as the Fe-only and Li-only (abbreviated as Fe-0.01 and Li-0.01) doped samples are prepared by a solid-state reaction method to investigate their colossal dielectric property for the first time. The permittivity value (approximate to 2.05x10(4) at 20 degrees C, 1kHz with tan approximate to 0.61) is the highest in co-doped ZnO ceramics reported so far. The colossal permittivity is brought out by the step-like dielectric abnormities over which goes up steeply (approximate to 10(1)-approximate to 10(4)) resulting from the mix-valent ions of Fe2+/Fe3+, while the grain boundaries tend to make the dominant contribution at elevated temperature above the step-like abnormity. The defect-dipole (Li+-Fe3+) can localize the electrons to a certain extent in the ZnO matrix inducing effective suppression of the dielectric loss. The sample FL-0.01 exhibits the optimal colossal dielectric property and as x goes up further, the dielectric loss tends to increase obviously. This work provides a new routine to design optimal colossal dielectric materials and related devices for research and applications.