Luminescent and thermal properties of full-color emitting X3MgSi2O8:Eu2+, Mn2+ (X=Ba, Sr, Ca) phosphors for white LED

The X3MgSi2O8:Eu2+, Mn2+ (X=Ba, Sr, Ca) phosphors show three emission peaks: the blue and green bands of Eu2+ transitions, and the red band of Mn2+ transitions. Three emission peaks are shifted toward longer-wavelength side with substituting X cations with smaller cations in the order of Ba, Sr, and Ca cations. This behavior is discussed in terms of two factors of the crystal-field strength and the covalence. As an increase of temperature, the red and green emission peaks show anomalous blueshift along with broadening bandwidth and decreasing intensity. This phenomenon is described in terms of the phonon-assisted back tunneling from the excited state of low-energy emission band to the excited state of high-energy emission band.