Up-conversion luminescence of Yb super(3+) and Er super(3+) doped YPO sub(4), LaPO sub(4) and GdPO sub(4) nanocrystals

• Published in: Journal of luminescence 2016-07, Vol.175, p.21-27
• Main Authors: Grzyb, Tomasz, Gruszeczka, Aleksandra, Lis, Stefan
• Format: Article
• Language: English
• Subjects: Annealing; Coprecipitation; Dopants; Energy transfer; Image transmission; Luminescence; Nanocrystals; Upconversion
• ISSN: 0022-2313
• DOI: 10.1016/j.jlumin.2016.02.021

In this article we report a comparison of structural and up-conversion (UC) luminescence properties of three compounds used as hosts for Yb super(3+) and Er super(3+) ions: YPO sub(4), LaPO sub(4) and GdPO sub(4) phosphates. A co-precipitation method connected with annealing at 900 degree C was used in order to synthesize nanocrystalline REPO sub(4):Yb super(3+),Er super(3+) materials (RE=Y, La, Gd). The X-ray diffraction patterns collected for the prepared materials indicated their high crystallinity and phase purity for the wide range of used dopants concentrations (0.25-7.5% of Er super(3+) and 5-30% of Yb super(3+) ions). Transmission electron microscopy images showed small nanocrystal sizes: around 20 nm for YPO sub(4)-based products, 30-50 nm for LaPO sub(4) or 40-150 nm for GdPO sub(4)-based materials. The nanomaterials prepared showed yellow UC under 980 nm laser irradiation, which was assigned to Er super(3+) electronic transitions. The optimal dopants concentration were determined, giving the highest UC intensity: 25% of Yb super(3+) ions (or 20% in the case of LaPO sub(4)) and 1% of Er super(3+) ions. Also the mechanism of observed UC was analyzed. Two- and three-photon excitation and energy transfer between Yb super(3+) and Er super(3+) were confirmed. The effect of crystal cell volume on the green to red ratio of Er super(3+) UC and the presence of Er super(3+)-Er super(3+) energy transfer were found.