Abstract
An electronic energy mechanism of activator and sensitizer was established to describe the luminescence behaviors of Eu- and Dy-codoped M(II)Al2O4 (M(II) = Ba, Sr, Ca, Mg) phosphors through potassium carbonate coprecipitation. Experimental results demonstrated that the prepared phosphors exhibited superior crystallinity at a temperature lower than 950 °C. The phosphors are ordered according to emission intensity as follows Ca- > Ba- > Sr- > Mg-containing phosphors. The energy level for Eu2+ 4f65d1 → 4f7, Eu3+4D0 → 7F, and Dy3+4F9/2 → 6H transitions and the effects of nephelauxetic and crystal field in Ba-, Sr-, and Ca-containing phosphors were discussed. The energy gap, (hv)em, between 5d and 4f of Eu2+ ion is strongly affected by host composition, crystal field strength, and nephelauxetic effect. The infrared emission of 4f9/2 → 6h for Dy3+ is merely depend on the transfer of energy from Eu2+ upon excited. Ca-containing phosphor with maximum (hv)em is attributed to the lowest bond length of CaO and highest ionization potential of Ca2+ ion, which leads to the effects of crystal field and nephelauxetic greater than that in the other phosphors.
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