Synthesis of luminescent nanocrystals and solid solutions in the YNbO_4-EuNbO_4 system via hydrothermal route

摘要

Luminescent nanocrystals having distinctive ellipsoidal morphology and the complete solid solution of monoclinic phase in the YNbO_4-EuNbO_4 system were hydrothermally formed under weakly basic conditions at 180-240℃ for 5h. The excitation spectra of the Y_(1-x)Eu_xNbO_4 nanocrystals, which consisted of the charge transfer (CT) band around 240-270 nm due to [NbO_4]~3~-Eu~(3+) interaction and several sharp bands corresponding to the f-f transitions of Eu~(3+), e.g. the most intense absorption band at 395 nm (~7F_0→~5L_6), showed that the compounds could be excited by both ultraviolet and visible light. A dominant red emission at 610 nm and a weak orange emission at 590 nm assigned to ~5D_0→~7F_2 and ~5D_0→~7F_1, transitions of Eu~(3+), respectively were observed in the as-prepared nanocrystals containing europium under excitation at 395 nm. The heat treatment at temperatures more than 1000℃ in air was effective for the improvement in the photoluminescence intensity of the as-prepared solid solutions. By the enhancement in the crystallinity and crystallite growth of the monoclinic phase through heat treatment at 1300 ℃ in air, the luminescence intensity of the as-prepared solid solution, Y_(0.75)Eu_(0.25)NbO_4 (x = 0.25), which showed the most significant photoluminescence, became more than 5 times as strong as that before the heat treatment.