Investigation on temperature stability performance of giant permittivity (In + Nb) in co-doped TiO2 ceramic: a crucial aspect for practical electronic applications
In this work, it was shown that the crucial aspect for practical applications of a newly discovered (In + Nb) co-doped TiO2 material is the temperature stability of its dielectric permittivity (ε′). Despite an extremely large ε′ value of ≈5.1 × 104 and a low loss tangent (tan δ ≈ 0.03) successfully obtained in 10% (In + Nb) co-doped TiO2, careful inspection revealed that ε′ was largely changed below room temperature (RT) as a result of an ambient-RT dielectric relaxation, giving rise to a large value of the temperature coefficient. However, this result can be effectively improved by decreasing the co-doping concentration. Although this dielectric relaxation also occurred in 2.5% (In + Nb) co-doped TiO2, its ε′ variation below RT was slight. Notably, very high ε′ ≈ 1.57 × 104 and ultra-low tan δ ≈ 0.006 (at 30 °C and 102 Hz) with an excellent temperature coefficient of less than ±7% in the range of −70 to 180 °C were achieved. The giant ε′ response over a broad temperature range in (In + Nb) co-doped TiO2 was primarily due to the polarization of highly localized electrons in large defect-dipole clusters. The additional polarization relaxation near the RT range might be associated with interfacial polarization of delocalized electrons originating from uncorrelated Nb25+Ti3+ATi defect dipoles.