Sol-Gel Combustion Synthesis, Crystal Structure and Luminescence of Cr3+ and Mn4+ Ions in Nanocrystalline SrAl4O7

Vitalii Stadnik,Yaroslav Zhydachevskyy,Andrzej Suchocki,Vasyl Hreb,Leonid Vasylechko,Andriy Luchechko

doi:10.3390/inorganics9120089

Vitalii Stadnik, Yaroslav Zhydachevskyy + Show 4 more

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https://doi.org/10.3390/inorganics9120089

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Abstract

A series of strontium dialuminate SrAl4O7 nanopowders with the grossite-type structure doped with chromium and manganese ions were synthesized by the combined sol–gel solution combustion method with use of two different strontium salts. The Cr3+ and Mn4+ ions concentrations were varied from 0.05 to 5 at.%. Evolution of phase composition, crystal structure, and microstructural parameters of the nanocrystalline materials depending on the synthesis conditions, temperature of thermal treatment, and dopant content were investigated by the X-ray powder diffraction and the scanning electron microscopy techniques. Photoluminescent properties of SrAl4O7 nanophosphors activated with Cr3+ and Mn4+ ions were studied at room temperature. The samples exhibit typical photoluminescence in the deep-red spectral region, corresponding to d-d transitions in Cr3+ or Mn4+ ions. The intensity of this deep-red emission is dependent on the dopant concentration and annealing temperature. Features of the formation of octahedral surroundings around Cr3+ or Mn4+ ions are discussed.

Highlights

Aluminates (MAl4O7) and gallates (MGa4O7) of alkaline earth elements (M = Ca, Sr, Ba) with the monoclinic grossite-type structure are promising for applications in white light sources (WLEDs), fluorescent lamps, optical amplifiers, radiant displays, solid-state lasers, radiation dosimetry, sensors, and radiographs
Phosphors doped with transition metal ions, Mn4+ or Cr3+, which have broadband excitation in the UV and visible regions of the spectrum and deep red radiation can be an alternative to phosphors activated by RE ions
Series of Cr3+ and Mn4+ doped strontium dialuminate SrAl4O7 nanophosphors with an average crystallite size of 65–115 nm were synthesized for the first time by the combined sol–gel solution combustion method

Summary

Introduction

A number of publications have appeared on the synthesis of MAl4O7-based materials doped with rare-earth elements (Eu, Dy, Nd, Sm), bismuth, as well as some transition elements such as Cr, Mn, and Cu [1–15]. Phosphors activated with rare-earth (RE) ions have attracted great attention since they show high quantum efficiency, long persistence of phosphorescence, and suitable emitting color. Phosphors doped with transition metal ions, Mn4+ or Cr3+, which have broadband excitation in the UV and visible regions of the spectrum and deep red radiation can be an alternative to phosphors activated by RE ions. There has been a growing interest in such inexpensive phosphors (without RE ions) for the deep-red and near-IR emission range.

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