Sr8MSm1-xEux(PO4)7 phosphors derived by different synthesis routes: Solid state, sol-gel and hydrothermal, the comparison of properties

Abstract

A series of new Sr-based phosphors Sr8M2+Sm1-х(PO4)7:xEu3+, M = Mg2+, Zn2+ with β-Ca3(PO4)2-type structure was synthesized and studied. The Sr8MgEu(PO4)7 was obtained by three types of synthetic routs: high temperature solid-state, hydrothermal and sol-gel methods. The influence of synthesis routes and annealing conditions on luminescent properties was studied and analyzed taking into account the data on average crystallite size and grain size determination. It was shown that the synthesis method has a defining role on the phosphor’s properties. The solid-state route gives the best powders crystallinity and the highest intensity of emission. The samples were characterized by strong emission in visible region at 615 nm originating from 5D0 → 7F2 transition of Eu3+ and 600 nm originating from the 5G5/2 → 4H7/2 transition of Sm3+. Also, it was revealed that Zn-substituted samples exhibit higher intensity than Mg-containing ones due to larger particle size and lower scattering of light and higher light absorption. Photoluminescence decay curves were measured and the dependence of decay times on activator concentrations was revealed. The CIE chromaticity coordinates were close to red standard. The prototypes of LED devices were characterized by strong emission with warm correlated color temperature. The investigated compounds can be used as a potential commercial phosphor for solid-state lighting application.