[Study on luminescence properties of Eu2+ in (Sr, Ca)4Si3O8Cl4 host lattice].

Alkali earth chlorosilicate of the type Sr(4-x)Ca(x)Si3O8Cl4 was synthesized through the high temperature solid state method. According to the Van Uitert experimental equation, luminescence properties and crystal-lattice environment of Eu2+ in Sr(4-x) Ca(x)Si3O8Cl4 crystal were discussed. The possibilities of two Eu2+ emission centers, viz. blue and greenish-yellow centers, were found and their corresponding relationships with spectra were also discussed. When the doping amount of calcium(x) varied between 0 and 0.5, Ca2+ ions were embedded in the host lattice of Sr4Si3O8Cl4, and the luminescence of blue center, which was ascribed to the emission of Eu2+ that substituted the octa-coordination Sr2+ sites, dominated and showed blue-green luminescence. Sr(4-x)Ca(x)Si3O8Cl4:yEu2+ exhibited greenish-yellow luminescence when the range of x was between 0.5 and 2. This was due to the fact that the Eu2+ emission originated from the formation of an impurity-trapped exciton state. Greenish-yellow emission center was located in the impurity-trapped exciton state which was the lowest excited state of this system, and the Eu2+ emission was at long wavelengths, and a large Stokes shift was observed.