Colossal dielectric response in erbium iron garnet ceramics

Polycrystalline Er 3 Fe 5 O 12 ceramic sample was synthesized by a solid-state reaction technique. The dielectric properties of the sample were experimentally studied. A colossal dielectric constant more than 10 3 was observed over a wide temperature and frequency range. The dielectric relaxation in the sample was identified by the measurement of permittivity modulus, impedance spectroscopy, and conductivity in detail. At relatively low temperatures ( T < 600 K), the dielectric relaxation under high frequencies ( f ≥ 50 kHz) is triggered by the dipolar effect accompanied by the Fe 2+ and Fe 3+ charge transitions, while that under low frequencies ( f ≤ 50 kHz) is mainly be associated with the Maxwell–Wagner effect. Moreover, a low-frequency dielectric relaxation at high temperatures ( T ≥ 600 K) is probably evolving from the contribution of oxygen vacancies and grain boundaries, which is also suggested to be the origin of the colossal dielectric constant.