Wydział Chemii

Mirosław Karbowiak

A. Mech

Artur Bednarkiewicz

Wiesław Stręk

2004

Journal of Alloys and Compounds

380

321-326

10.1016/j.jallcom.2004.03.030

Naukowa

Angielski

Artykuł

The single-phase low-temperature cubic form of KGdF₄, with the average crystallites size of 19 nm precipitates from a solution. The cubic phase is stable up to approximately 460 °C. At higher temperatures the cubic KGdF₄ transforms, first to the orthorhombic and then to the trigonal phase, however, the transformation is not complete and the cubic form is still present. The highest concentrations of orthorhombic and trigonal phases were observed at temperatures of 540 and 720 °C, respectively. The single-phase high-temperature cubic form of KGdF₄ was obtained when the as-received sample was heated at 790 °C. In contrast to a coprecipitation (CP) method, the single-phase orthorhombic modification of KGdF₄ was obtained by a solid state (SS) reaction conducted at 650 °C. In excitation spectra recorded for CP samples the characteristic Eu³⁺–O²⁻ CT bands expected at ∼260 nm are not present, which indicates that oxygen impurities are practically absent. However, both IR spectra and the emission branching ratio points to the presence of OH⁻ groups incorporated into a fluoride lattice and a heat treatment at temperature of at least 650 °C is indispensable to get rid of them. Emission spectra for samples with different processing conditions were recorded and are discussed.

Phosphors, Nanostructures, Morphology, Precipitation, Luminescence, KGdF4

https://doi.org/10.1016/j.jallcom.2004.03.030

http://www.elsevier.com