Europium doped vanadium dioxide material: Reduced phase transition temperature, enhanced luminous transmittance and solar modulation

Vanadium dioxide is a well-known near room temperature phase transition material with a transition temperature (τC) at 68 °C. In this paper, Eu³⁺ dopant with different doping levels was introduced into the crystal lattice of VO₂. The thermochromic properties, including the integrated visible transmittance (T_lum and the solar modulating ability (ΔT_sol were favorably affected by the Eu-doping. It is of great interest that the substitution of V⁴⁺ by Eu³⁺ in the VO₂ crystal structure reduced the τC from 68 °C to 47.5 °C with an approximate decreasing rate of 6.5 °C/at% up to 4 at%. More importantly, the Eu dopant helped in improving the properties of luminous transmittance and solar modulating ability, which were difficult to be achieved by other dopants.