Eu2+ as the structural probe in the phase transformation of CMSA by site-selective occupancy and adjustable multimode white luminescence in Ca2(Mg0.5Al0.5)(Si1.5Al0.5O7) akermanite based on high-aluminum blast furnace slag

Abstract

A tunable multimode white emission Ca₂(Mg_0.5Al_0.5)(Si_1.5Al_0.5O₇):Eu²⁺/Eu³⁺ phosphor was prepared by doping Eu₂O₃ in molten high-aluminum blast furnace slag. The structural probe Eu²⁺ was studied during phase transformation between the glassy state and Ca₂(Mg_0.5Al_0.5)(Si_1.5Al_0.5O₇) crystals based on site-selective Eu²⁺ occupancy. When the doped Eu²⁺ ions occupied two different Ca²⁺ sites in the matrix, blue light (421 nm) and green light (516 nm) emissions were observed corresponding to two types of Eu²⁺_Ca²⁺, namely Eu²⁺_Ca²⁺ (Mg²⁺ → Al³⁺) and Eu²⁺_Ca²⁺ (Si⁴⁺ → Al³⁺). The effects of Eu concentration (0.1–2.0 mol%), heat treatment temperature (800–1000 °C), and thermal quenching temperature (30–150 °C) on the structural evolution of the emission unit were studied by differential scanning calorimetry (DSC), photoluminescence spectroscopy (PL) and X-ray diffraction (XRD) analyses. The Eu²⁺_Ca²⁺ (Mg²⁺ → Al³⁺) structure formed by site-selective Eu²⁺ occupancy possessed better structural stability in the Ca₂(Mg_0.5Al_0.5)(Si_1.5Al_0.5O₇) crystal matrix, in favour of light-emitting diode (LED) illumination and plasma display panels (PDPs).