Investigation of the Fabrication Parameters Affecting the Cathodoluminescence Property of ZnAl2O4:Mn Green Phosphors

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We investigated systematically the effects of fabrication parameters on the luminescent property of ZnAl2O4:Mn phosphor, which emits a highly chromatic pure green light. The samples used were synthesized in the air at 1200 °C by a solid phase method using ZnO, $\alpha$-Al2O3, and MnCl2 or MnCO3 powders, followed by thermal treatment in a reducing atmosphere at temperatures ($T_{\text{r}}$) from 800 to 1200 °C. We confirmed that the cathodoluminescence (CL) property of the as-synthesized sample strongly depends on the molar ratio of Zn and Al atoms in the source ($R_{\text{Zn/Al}}$). Namely, intense CL was observed only from the samples synthesized from the source with $R_{\text{Zn/Al}} < 0.5$, indicating that the Zn-deficient conditions are favorable for Mn impurities to be incorporated into the Zn site of ZnAl2O4. More importantly, it is suggested from the $T_{\text{r}}$ dependence of CL that most of the Mn impurities in the samples synthesized under the Zn-deficient conditions are in the state of the divalent ions even without a reduction treatment.
2009-09-25