To tune europium valence by controlling the composition in diphase silicate phosphors

Commercial phosphors always require fewer impurities and higher crystallinity, but sometimes it is difficult or strict to synthesize a pure phase compound. Indeed, if the practical application is not influenced, it is acceptable to synthesize a kind of phosphors with diphase matrix that have similar structure and photoluminescence properties. In present work, we designed and synthesized a series of (1-x) BaMSiO4 center dot xBa(2)MSi(2)O(7):Eu (M = Zn2+, Mg2+) diphase phosphors which contained two phases BaMSiO4 (hexagonal, P6(3)) and Ba2MSi2O7 (monoclinic, C2/c) by a high temperature solid-state reaction in air condition. The structures and luminescence properties related to the phase transform from BaMSiO4 to B(a)2MSi(2)O(7) were analyzed carefully. The results show that the self-reduction ability of Eu3+ is not the best in above four compounds, respectively. But it reaches the maximum and gets the green emission under the UV lamp when the matrix is in a proper ratio of two phases, which suggests that the heterostructure between the two crystals (BaMSiO4 and Ba2MSi2O7) improves the self-reduction process of the diphase. The possible mechanism of the tunable europium valence and the luminescent properties in (1-x) BaMSiO4 center dot xBa(2)MSi(2)O(7):Eu phosphors were discussed in detail. (C) 2018 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.