Synthesis and optical properties of La2O2CO3:Eu3+ hollow sphere phosphors by hydrothermal synthesis assisting with double-crucible carbonization method

Abstract

Lanthanum oxide, europium oxide, hydrochloric acid, ammonia water, and carbon powder were used as the starting materials. Detailed characterizations were attained by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry/differential thermal analysis (TG-DTA), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy. The La(OH)3 precursor was synthesized by an hydrothermal synthesis method at 120 °C for 24 h, which was then converted into La2O2CO3 phase through calcining the precursor at 800 °C for 2 h in a carbon atmosphere. It was demonstrated that the as-obtained La2O2CO3 is a hollow sphere with uniform size about 200 nm. The formation mechanism of the La2O2CO3 phase has also been proposed. Photoluminescence analysis showed that the La2O2CO3:Eu3+ phosphors have the strongest red emissions at 614 nm under 281 nm ultraviolet (UV) light excitation, which correspond to the 5D0 → 7F2 transition of Eu3+ ions. The La2O2CO3:Eu3+ phosphors have double-exponential decay behavior and the calculated lifetime is determined to be t1 = 0.205 μs and t2 = 1.177 μs.