(Sr,Ca)4Si3O8Cl4基质中Eu2+的发光特性研究

采用高温固相法合成Sr4-xCaxSi3O8Cl4：Eu^2＋荧光材料，利用Van Uitert公式讨论Sr4-xCaxSi3O8Cl4：Eu^2＋中yEu^2＋的晶格环境和发光特性，确定晶体中有蓝色和黄绿色两种发光中心，并讨论了它们与光谱结构的对应关系。当0〈x〈0．5，Ca^2＋固溶入Sr4Si3O8Cl4基质晶格，Eu^2＋占据八配位Si^2＋格位，晶体主要产生蓝色中心的蓝绿色发射；当0．5〈x〈2，较大的Ca^2＋掺杂使晶胞参数变小，品格中的杂质束缚激子态的束缚增强，Eu^2＋处于杂质束缚激子中心所形成的激发态能量进一步降低，发射位于长波段方向并具有较大的Stokes位移，Sr4-xCaxSi3O8Cl4：yEu^2＋主要产生黄绿色中心的黄绿色发射光。

Study on Luminescence Properties of Eu2+ in (Sr, Ca)4Si3O8Cl4 Host Lattice

Alkali earth chlorosilicate of the type Sr_(4-x)Ca_xSi_3O_8Cl_4 was synthesized through the high temperature solid state method.According to the Van Uitert experimental equation,luminescence properties and crystal-lattice environment of Eu~(2+) in Sr_(4-x)Ca_xSi_3O_8Cl_4 crystal were discussed.The possibilities of two Eu~(2+) 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,Ca~(2+) ions were embedded in the host lattice of Sr_4Si_3O_8Cl_4,and the luminescence of blue center,which was ascribed to the emission of Eu~(2+) that substituted the octa-coordination Sr~(2+) sites,dominated and showed blue-green luminescence.Sr_(4-x)Ca_xSi_3O_8Cl_4:yEu~(2+) exhibited greenish-yellow luminescence when the range of x was between 0.5 and 2.This was due to the fact that the Eu~(2+) 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 Eu~(2+) emission was at long wavelengths,and a large Stokes shift was observed.