Phase transition and luminescence properties of GdTiNbO6:Eu3+ formed by hydrothermal route
Highlights: • Phase transition and luminescence of hydrothermal GdTiNbO{sub 6}:Eu{sup 3+} were investigated. • RE{sup 3+} radius 0.1061 nm was the boundary between the aeschynite and euxenite. • GdTiNbO{sub 6}:0.30Eu{sup 3+} was preferred for UV-B excitation, 0.50Eu{sup 3+} for Vis-light excitation. • The decay lifetime of 615 nm emission (ex = 405 nm) was 570∼571 μs. - Abstract: The dependences of phase transition and luminescence properties upon both Eu{sup 3+} concentration and heating temperature in air were investigated for GdTiNbO{sub 6}:Eu{sup 3+} fine crystals formed hydrothermally at 240 °C as aeschynite-type Eu{sub x}Gd{sub 1-x}TiNbO{sub 6} solid solution. The as-prepared aeschynite solid solution in the concentration range x ≥ 0.70 did not show the phase transformation from an aeschynite- to an euxenite-type structure caused by heating at 1300 °C for 1 h in air. The present study suggested that the phase boundary between the aeschynite- and euxenite-type RETiNbO{sub 6} in the EuTiNbO{sub 6}-GdTiNbO{sub 6} system, where RE was a rare earth, lay in the average RE{sup 3+} ionic radius 0.1061 nm. The intense emissions attributed to the {sup 5}D{sub 0}→{sup 7}F{sub 1} and {sup 5}D{sub 0}→{sup 7}F{sub 2} transitions of Eu{sup 3+} for the as-prepared samples were more improved by heating at 1100–1300°C in air. The material doped with 30 mol% Eu{sup 3+} was preferred for UV-B excitation, in contrast, the material with 50 mol% Eu{sup 3+} was preferred for visible light excitation.