Fig. 2
Thermal conductivity of anatase single-crystals. a Temperature dependence of the thermal conductivity of insulating-transparent, brown and conducting-black anatase TiO2 single-crystals, respectively from higher to lower κ. The solid lines are fits of κ including the resonant-dynamical-scattering term. Sketches of the difference between heat propagation in b pristine single-crystal and in c crystal with oxygen vacancies. Only one vacancy is displayed with an electron localised in its surrounding. Such defects exhibit strong polaronic effects, which heavily scatter phonons and reduce κ. The colour gradients from red to blue illustrate temperature differences across the material. Experimental error at 300 K is 15%, and decreases with lowering temperature as the black-body-radiation contribution diminishes
