Microstructure, doping and optical properties of Co2+:ZnAl2O4 transparent ceramics for saturable absorbers: Effect of the ZnF2 sintering additive

Transparent cobalt-doped zinc aluminate spinel (gahnite), Co2+:ZnAl2O4, ceramics were fabricated by hot pressing of (Zn,Co)Al2O4/ZnF2 nanopowders at 1520 °C for 4 h. A novel approach was suggested for the preparation of (Zn,Co)Al2O4 precursor: the (Zn,Co)Al2O4 powders were synthesized by mixing an a...

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Bibliographic Details
Published in:Journal of alloys and compounds 2020-07, Vol.829, p.154514, Article 154514
Main Authors: Belyaev, Alexander, Basyrova, Liza, Sysoev, Vadim, Lelet, Maxim, Balabanov, Stanislav, Kalganov, Vladimir, Mikhailovski, Vladimir, Baranov, Mikhail, Stepanidenko, Evgeniia, Vitkin, Vladimir, Dymshits, Olga, Loiko, Pavel
Format: Article
Language:English
Subjects:
Absorbers
Aluminum
Aqueous solutions
Ceramics
Chemical Sciences
Cobalt
Cobalt ions
Doping
Erbium
Gahnite
Grain size
Hot pressing
Hot pressing synthesis
Inorganic chemistry
Material chemistry
Microstructure
Optical properties
Precursors
Roasting
Saturable absorbers of lasers
Sintering
Sintering (powder metallurgy)
Sintering additive
Spinel
Thermodynamic properties
Transparent ceramics
Zinc fluorides
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Summary:Transparent cobalt-doped zinc aluminate spinel (gahnite), Co2+:ZnAl2O4, ceramics were fabricated by hot pressing of (Zn,Co)Al2O4/ZnF2 nanopowders at 1520 °C for 4 h. A novel approach was suggested for the preparation of (Zn,Co)Al2O4 precursor: the (Zn,Co)Al2O4 powders were synthesized by mixing an alcohol solution of aluminium isopropoxide with a joint aqueous solution of zinc formate (the source of zinc), cobalt nitrate and zinc fluoride (the sintering additive) followed by drying and calcination in air. The study of the thermal behavior of precursors revealed an optimum calcination temperature (700 °C) preventing the loss of the sintering additive (ZnF2). The effect of the ZnF2 content (3–10 wt%) on the microstructure, the cobalt doping concentration, absorption and luminescence of ceramics was systematically studied. The ceramics exhibit a close-packed microstructure with a mean grain size of 50–70 μm and high in-line transmission (about 84% at ∼2 μm). The actual concentration of Co2+ ions in tetrahedral (Td) sites of gahnite is lower than the Co2+ doping level and it decreases with the ZnF2 content. We propose a possible mechanism of this variation including both the losses of Co2+ via evaporation of the intermediate CoF2 phase and a partial location of Co2+ ions in octahedral (Oh) sites of gahnite due to its partly inverse spinel structure. The developed ceramics are promising for saturable absorbers of erbium lasers. •Transparent cobalt-doped zinc aluminate spinel Co2+:ZnAl2O4 (gahnite) ceramics.•A novel approach suggested for the preparation of (Zn,Co)Al2O4 precursors.•Synthesis of ceramics by hot pressing of (Zn,Co)Al2O4/ZnF2 nanopowders at 1520 °C.•The effect of the sintering additive (ZnF2) on the structure and optical properties.•Discussion of mechanisms of decreased Co2+ concentration in tetrahedral (Td) sites.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2020.154514