Small-polaron-induced infrared opacification in rutile TiO2

I. González de Arrieta (1, 2) , L. González-Fernández (2, 3) , T. Echániz (2) , L. del Campo (1) , D. de Sousa Meneses (1) , G. López (2)

1 CEMHTI - Conditions Extrêmes et Matériaux : Haute Température et Irradiation
2 UPV/EHU - Universidad del Pais Vasco / Euskal Herriko Unibertsitatea [Espagne]
3 CIC ENERGIGUNE - Parque Tecnol Alava

The infrared emittance of single-crystal rutile TiO2 has been measured from room temperature to 2000 K in dry air for two polarization states. A very strong thermally-induced opacification phenomenon has been found, with the sample being completely opaque in the near-infrared range several hundred K before its melting point. A large contribution from small-polaron hopping conduction can explain this anomalous degree of opacification, much stronger than similar phenomena present in other octahedrally coordinated oxide materials. These quasiparticles manifest in the high-temperature optical conductivity as a thermally-activated contribution, with an activation energy close to that of DC conductivity. The small-polaron nature of this phenomenon is strengthened by the observation of broad near-infrared bands.

Domaines: Science des matériaux [cond-mat.mtrl-sci]

I. González de Arrieta, L. González-Fernández, T. Echániz, L. del Campo, D. de Sousa Meneses, et al.. Small-polaron-induced infrared opacification in rutile TiO2. Journal of Applied Physics, 2021, 130 (7), pp.075105. ⟨10.1063/5.0056081⟩. ⟨hal-03563916⟩