Investigation on temperature stability performance of giant permittivity (In plus 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 (epsilon'). Despite an extremely large epsilon' value of approximate to 5.1 x 10(4) and a low loss tangent (tan delta approximate to 0.03) successfully obtained in 10% (In + Nb) co-doped TiO2, careful inspection revealed that epsilon' 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 epsilon' variation below RT was slight. Notably, very high epsilon' approximate to 1.57 x 10(4) and ultra-low tan delta approximate to 0.006 (at 30 degrees C and 10(2) Hz) with an excellent temperature coefficient of less than +/- 7% in the range of -70 to 180 degrees C were achieved. The giant epsilon' 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.