Rare-earth iron garnets (RIG, R = Y, Tb and Lu) were sintered at 1350 °C.
A similar Fe2+/Fe3+ ratio (∼27/73) was measured in different RIGs.
Electron hopping between FeO6 and FeO4 resulted in a large dielectric response.
Debye-type dielectric relaxation was dominant at room temperature.
Maxwell-Wagner effect had a significant contribution at elevated temperature.