Luminescent Properties of Mn4+Impurity Center-induced Mg7 Ga2 GeO12∶Tb3+Multicolor Phosphor
Study on high-performance multicolor luminescent materials activated by rare-earth ions is the necessary foundation for developing advanced fluorescent anti-counterfeiting techniques.In this paper,a series of Tb3+-doped Mg7Ga2GeO12 phosphors were prepared by a traditional high-temperature solid-state method.With the help of X-ray powder diffraction(XRD),scanning electron microscopy(SEM),and energy-dispersive X-ray spectroscopy(EDS),phase identification,particle size and morphologies,and element mapping were systematically character-ized and analyzed.All the results verified the successful preparation of well-crystallized pure phase Mg7Ga2GeO12∶x%Tb3+powders with irregular shapes and micrometer size distribution.Under excitation of 377 nm,the Mg7Ga2GeO12∶Tb3+sample efficiently produced several typical blue-green emission bands,respectively increasing to maximum val-ues at 20%Tb3+.Interestingly,there surprisingly presents a single red emission band around 660 nm,disaccording with any electronic transitions of Tb3+.On basis of inductively coupled plasma mass spectrometry(ICP-MS),steady/dynamic fluorescence spectra,as well as literature investigation,it was proved that the red～660 nm emission is from Mn4+2Eg →4A2g transitions and the Mn impurity element was introduced from the raw materials.However,just benefiting from the combined luminescence properties of Tb3+and Mn4+ions,the Mg7Ga2GeO12∶Tb3+sample behaved tunable photoluminescence in response to the excitation-wavelength in 200-420 nm,which can display cyan,green,yellow,white and red colors for much distinguishable observations.These results would consolidate the fundamental materials and techniques for applications in multicolor fluorescent anti-counterfeiting.
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