Effects of sintering atmosphere on microstructure and dielectric properties of (Yb + Nb) co-doped rutile TiO2 ceramics

(Yb1/2Nb1/2)0.05Ti0.95O2 ceramics are fabricated by the solid state reaction method. The effects of oxygen partial pressure in the sintering atmosphere (10% ≤ x ≤ 100%) on crystal structures, microstructure and dielectric properties of (Yb1/2Nb1/2)0.05Ti0.95O2 are investigated. All samples have rutile structure, and average grain size rises from 5 μm to 28 μm with x increasing from 10% to 100%. All samples show colossal permittivity (above 104). The dielectric properties of x ≥ 50% samples show well temperature (120 K-370 K) and frequency stability (100 Hz-100 kHz). The grain resistivity of x = 100% sample is three orders of magnitude higher than that of x = 10%. The breakdown voltage improves from 246 to 716 V/cm with increasing oxygen partial pressure. Both the Ti valence and oxygen concentration have been influenced by sintering atmosphere.