Colossal permittivity with ultralow dielectric loss in In + Ta co-doped rutile TiO2Electronic supplementary information (ESI) available. See DOI: 10.1039/c6ta08337d

Colossal permittivity (CP) materials have many important applications in electronics but their development has generally been hindered due to the difficulty in achieving a relatively low dielectric loss. In this work, we report an In + Ta co-doped TiO 2 material system that manifests high dielectric permittivity and low dielectric loss based on the electron-pinned defect-dipole design. The dielectric loss can be reduced down to e.g. 0.002 at 1 kHz, giving high performance, low temperature dependent dielectric properties i.e. r > 10 4 with tan δ < 0.02 in a broad temperature range of 50-400 K. Density functional theory calculations coupled with the defect analysis uncover that electron-pinned defect dipoles (EPDDs), in the form of highly stable triangle-diamond and/or triangle-linear dopant defect clusters with well-defined relative positions for Ti reduction, are also present in the host material for the CP observed. Such a high-performance dielectric material would thus help for practical applications and points to further discovery of promising new materials of this type. Electron-pinned defect dipoles, in the form of highly stable triangle-diamond and/or triangle-linear dopant defect clusters with well defined relative positions for Ti reduction, are present in rutile In + Ta co-doped TiO 2 for the colossal permittivity and low loss.