Hydrothermal synthesis, structural investigation, photoluminescence features, and emission quantum yield of Eu and Eu-Gd silicates with apatite-type structure

abstract

For the first time, Eu8.18Na1.08(SiO4)(6)(OH)(1.62-2y)O-y (Eu apatite) and Eu3.96Gd3.96Na1.2(SiO4)(6)(OH)(1.86-2y)O-y (Eu-Gd apatite) were synthesized at mild hydrothermal conditions. Powder X-ray analysis suggested a preferential substitution of Ln(3+) by Na+ ions in 4f position for both materials. The substitution of Eu3+ by Gd3+ ions alters the distribution of the Ln(3+) ions between 4f and 6h sites, which impacts their local symmetry, optical properties, and quantum efficiency. These materials are efficient room-temperature emitters with a maximum external quantum yield of ca. 21.4%. The abnormal increase in the relative intensity of the Eu3+ intra-4f(6) D-5(0) -> F-7(4) transition is attributed to the presence of interstitial oxygen or incommensurate ordering of the oxygen around the 6h position, which results in a distortion of the Eu3+ local symmetry. Evidence of concentration quenching effects will be discussed based on the 5D0 lifetime and the emission quantum yield dependence on the Eu3+ concentration.

keywords

RARE-EARTH SILICATES; OXIDE-ION CONDUCTORS; OXYAPATITES; ND; STABILIZATION; LUMINESCENCE; CALCIUM; LASER; PR; SM

subject category

Chemistry; Materials Science

authors

Ferdov, S; Ferreira, RAS; Lin, Z

our authors

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