engleski

Structural study of nanocrystalline Ti-doped gahnite

Titanium doped materials with spinel-type structure have been interesting as the active media for solid-state lasers. Among them, Ti-doped spinel (MgAl2O4:Ti) was found to have strong blue luminescence at ~490 nm, while Ti-doped α-ZnAl2S4 spinel-type crystals exhibit luminescence in the IR spectral range 0.8-1.4 µm. In both described cases, the emission bands arose from Ti4+ on spinel octahedral cation site. We have studied titanium incorporation in gahnite, ZnAl2O4. Gahnite is cubic with the normal spinel structure, space group Fd-3m. When doped with Co2+, Mn2+ or rare-earth ions it exhibits luminescence and can be used as a cathodoluminescent material. There is no literature data on titanium doped gahnite. Powder samples of gahnite doped with titanium were prepared by a sol-gel technique using zinc nitrate hexahydrate, aluminum-sec-butoxide and titanium(IV) butoxide as starting components. The excess of zinc component was used for the purpose of charge balance in the prepared samples. Samples could be described by formula Zn(Al2-2xTixZnx)O4, with 0.25 ≥ x ≥ 0.04. XRD patterns indicated that all samples had the characteristic spinel-type structure. Unit-cell parameter a was refined by WPPF program. The unit cell increased with the increase of Ti-doping level. Rietveld structure refinement confirmed that Ti4+ was incorporated on octahedral cation site in the normal spinel-type structure of gahnite with Zn excess. The prepared samples exhibited luminescence at ~470 nm.

Ti-doped gahnite; Spinel structure; Sol-gel technique; X-ray powder diffraction; Rietveld method

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