Structure and dielectric relaxation behaviors of Co-doped YMnO3 multiferroic ceramics

Rare-earth manganite YMnO3 have attracted much attention due to the simultaneous existence of ferroelectricity and magnetism in the same phase. In the present work, we report the results of the studies on the structural and dielectric relaxation behaviors of YMn1-xCoxO3 (x = 0.00, 0.03, 0.05, and 0.07) ceramics synthesized by conventional solid-state reaction method. The X-ray diffraction patterns confirm the existence of a single phase in YMn1-xCoxO3 with hexagonal structure belonging to P6(3)cm space group. A shifting of Raman-active phonon modes toward lower frequencies has been observed upon Co substitution. The structural morphologies analysis from the scanning electron microscope indicates a decrease in average grain size from 2.20 to 1.90 mu m with increasing Co content in the system. The dielectric constant and dielectric loss decrease with the increase of frequency at the temperature between 350 and 650 K and exhibit typical relaxation behaviors. It was a thermally activated process and the dielectric loss peak obeys Arrhenius law. This relaxation is attributed to the pinning effect of the local electric field generated by the dipole on the domain wall due to Co doping in the system. Oxygen vacancies are suggested to be responsible for the dielectric constant decrease with doping at the temperature above 700 K.