2019 Volume 127 Issue 8 Pages 570-580
Effect of processing conditions on the crystallinity and luminescent characteristics of aeschynite-type Dy3+- and Eu3+-doped GdTiNbO6 formed under hydrothermal conditions from precursor solutions of inorganic salts, i.e. Dy(NO3)3, EuCl3, GdCl3, TiOSO4, and NbCl5 was investigated. A processing condition using the hydrolysis of urea promoted the formation of aeschynite with finer crystallite due to an increase in nucleation number. The aeschynite-type solid solution was directly formed under hydrothermal conditions at 240°C because its lattice parameters changed according to the Vegard’s Law. The photoluminescence (PL) emission intensity of aeschynite crystals depended on their crystallinity, which was closely related to their processing conditions. Without subsequent heat treatment in air, the as-prepared aeschynite-type solid solutions substitutionally doped with 5 mol % Dy3+ and 50 mol % Eu3+ showed the maximum and intense PL emissions under direct excitation of dopant ions. In the case of indirect excitation using energy transfer from the host absorption band at 280 nm, the characteristic blue and yellow PL emission intensities involved in the broad host emission of the Dy3+-doped GdTiNbO6 were improved dramatically after heating at 1300°C in air.