On the structures and luminescence properties of Eu3+‐doped Li2CaGeO4, Ca2GeO4, and Ca5Ge3O11 compounds

Powder samples of Li2CaGeO4, Ca2GeO4, and Ca5Ge3O11 doped by 0.5, 1, 2, 3, 4 and 5 at% Eu3+ relative to the Ca2+, were prepared using a conventional solid‐state synthesis technique. X‐ray diffraction (XRD) analyses confirmed obtaining the pure phases at all dopant concentrations. In parallel, single...

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Published in:Luminescence (Chichester, England) England), 2022-09, Vol.37 (9), p.1492-1503
Main Authors: Koseva, Iovka, Nikolov, Velin, Nikolova, Rosica, Tzvetkov, Peter, Ivanov, Petar, Petrova, Petia, Tomova, Reni, Kuvandjiev, Nikola, Tarassov, Mihail
Format: Article
Language:English
Subjects:
Calcium ions
chemical synthesis
crystal growth
Crystal structure
Crystals
Distance
Dopants
Europium
inorganic compounds
Ion concentration
Luminescence
Optical properties
Phosphors
Polyhedra
Single crystals
X‐ray diffraction
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Summary:Powder samples of Li2CaGeO4, Ca2GeO4, and Ca5Ge3O11 doped by 0.5, 1, 2, 3, 4 and 5 at% Eu3+ relative to the Ca2+, were prepared using a conventional solid‐state synthesis technique. X‐ray diffraction (XRD) analyses confirmed obtaining the pure phases at all dopant concentrations. In parallel, single crystals of the three compounds with the experimentally found optimal Eu3+ concentration were grown using a flux method. Structural investigation on the single crystals were done with a special attention to the form of the Ca–O polyhedron, the mean Ca–O distance, the Ca–Ca distance in the structure, the distortion degree of the polyhedron, as well as the Eu–Ca substitution site. The main spectral characteristics were analyzed and several relationships between the structural and spectra features were found. The optimal dopant concentration was 3 at% for Ca2GeO4 and 4at% for Ca5Ge3O11 and Li2CaGeO4. Commission Internationale de l'éclairage coordinates of the samples showed emission colours in the red region close to the standard red coordinates and slightly influenced by the active ion concentration. The obtained results showed that europium‐doped Li2CaGeO4, Ca2GeO4, and Ca5Ge3O11 could be used as red phosphors. Europium‐doped powder Li2CaGeO4, Ca2GeO4, and Ca5Ge3O11 samples are prepared. Europium‐doped Li2CaGeO4, Ca2GeO4, and Ca5Ge3O11 single crystals are grown. Emission and excitation spectra of powder samples and single crystals are presented. Several relationships between the structural and spectra features are presented. Samples emitting red colours are obtained.
ISSN:1522-7235
1522-7243
DOI:10.1002/bio.4322