Abstract:

Pure YVO₄ crystal and YVO₄ crystal doped with different Ce concentrations were grown by Czochralski method. XRD pattern shows Ce³⁺ ion enters the YVO₄ lattice by occupying the Y³⁺ site and the crystal structure was not significantly changed. The detection of UV excitation spectrum and emission spectrum of YVO₄: Ce³⁺ at room temperature showed that excited at 325 nm the YVO₄: Ce³⁺ emits two spectra. The main emission spectrum at 445 nm is a broadband peak, caused by transition of ²D_3/2→²F_5/2 of Ce³⁺. The other one is a weak peak emission centered around 620 nm, which presents the emission of V⁴⁺. With increase of Ce mole fraction from 1at% to 8at%, the blue emission intensity gradually increases to a maximum value. As Ce fraction increases to 10.0at%, the emission intensity decreases gradually, indicating an obvious concentration quenching. The red emission intensity gradually increases to a maximum value when Ce fraction increases to 10.0at%. Detection by X-ray photoelectron spectroscopy (XPS) shows that Ce⁴⁺ and V⁴⁺ ions coexist in YVO₄:Ce³⁺, which may result from some of the Ce³⁺ losing electrons to be oxidized into Ce⁴⁺, and most of them being captured by the V⁵⁺ ions and, therefore, resulting in V⁵⁺→V⁴⁺ transformation. Based on V⁴⁺ d orbital splitting into ²A₁, ²B₁, ²B₂, and ²E, the 620 nm red emission under 325 nm and 450 nm excitation probably originated from electronic transitions between the V⁴⁺splitted d orbits. In conclusion, present analytical data of the luminescence spectra of YVO₄: Ce³⁺ provide a theoretical support for YVO₄:Ce³⁺ emitting red light and blue light simultaneously under UV excitation.

Key words: Ce³⁺, up-conversion, V⁴⁺, energy transfer, red-emitting