Near infrared and charge transfer luminescence of Yb-doped LaPO4 at room temperature

The Yb³⁺-doped LaPO₄ was prepared by hydrothermal reaction under fine acidity control and identified by X-ray diffraction and FT-IR spectroscopy. The obtained powders crystallize in the monoclinic phase of LaPO₄. The spectroscopic study at room temperature (RT) of the Yb³⁺-doped LaPO₄ powder was investigated. Thus a wide band, characteristic of the fundamental ²F_5/2↔²F_7/2 transition in near infrared (NIR) range, has been located for La_(1−x)Yb_xPO₄ (x = 5, 10%). Four Stark levels of the ground ²F_7/2 state are located on the emission spectra between 976 nm and 1030 nm, after excitation at 925 nm. Low re-absorption of the 0-phonon transition was registered. Charge transfer band (CTB) luminescence of Yb³⁺, which is not observed in LaPO₄ in later works, was appeared under 266 nm excitation. In the UV–Visible spectra, double band typical for the CTB luminescence of Yb³⁺ are observed. The decay time dependence as a function of the concentration is also reported and compared to other works. The room temperature radiative lifetimes of the IR emission and charge transfer band luminescence are compatible with potential applications of this phosphor respectively as solid-state lasers and scintillators.