Abstract:

YVO₄ and YVO₄:Ce³⁺ single crystals doped with 2.0at% CeO₂ (or Ce₂(CO₃)₃) were grown by using the Czochralski method. XRD pattern shows that Ce³⁺ ion enters the YVO₄ lattice by occupying the Y³⁺ sites and the YVO₄ crystal structure change little by the addition of Ce ions. The X-ray photoelectron spectroscopy (XPS) shows that the Ce (3d) peak splits into five peaks located at 882.0, 885.8, 902.9, 908.0 and 915.9 eV, which indicates that the Ce³⁺ and Ce⁴⁺ ions coexist in both kind of samples. The excitation spectra of YVO₄ and YVO₄:Ce³⁺ crystals are both in the range from 260 nm to 360 nm, due to the charge transfer transition of the O^2--V⁵⁺ ion pairs of VO₄^3- polyhedron. YVO₄ and YVO₄:Ce³⁺ single crystals radiate a wideband blue light centered at 440 nm when excited by 325 nm ultraviolet light, the former corresponds to ³T₂→¹A₁ and ³T₁→¹A₁ transition of VO₄^3-, while the latter corresponds to 5d→4f transition of Ce³⁺. In YVO₄: Ce³⁺ crystal, the wave functions of Ce³⁺ overlaps effectively to the π orbital of VO₄^3-, via this interaction the energy can be transfer effectively from VO₄^3- to Ce³⁺, so that the blue-emitting intensity of Ce³⁺ is improved significantly. Experimental results show that YVO₄: Ce³⁺ crystal is a potential blue-emitting material for white-emitting LED under ultraviolet excitation.

Key words: YVO4: Ce3+, blue-emitting, ultraviolet excitation, energy transfer, white LED