Résumé:
The aim of this work is to develop and characterize the single crystals of alkali
halide (KCl and KBr) doped with rare earth elements (Er, Ce and Lu) using the crystal
growth technique from melt phase according to the principle of the Czochralski method.
The single crystals obtained are on cylindrical morphology. For the purposes of their
characterization, the single crystals are cut by pellet cleavage whose plane faces are
perpendicular to the growth axis which is parallel to the crystallographic axis of KCl or
KBr.
Structural studies on elaborated materials using X-ray diffraction, FT-IR and
Raman spectroscopies have shown that the KCl and KBr monocrystals (pure and
doped) have a monocrystalline character, and in these crystalline matrices theaggregates
of rare earths elements (ErCl3, CeCl3 and Lu2O3) are incorporated. The presence of
these aggregates induced stresses in the crystal lattice of the matrices KCl and KBr.
Certain impurities such as H2O and CO2 have also been revealed and their come from
the environment during the growth operation (uncontrolled atmosphere) or the
characterization of the samples.
Optical investigations by absorption, photoluminescence and radioluminescence
were carried out to demonstrate the optical properties of KCl and KBr single crystals
doped with rare earth elements Er, Ce and Lu and also to confirm the presence of
dopants in the host matrices. Observation of the optical absorption spectra shows that
all the samples studied are transparent in the IR domain but have an important
absorption in the UV-VIS domain. Bands corresponding to the absorption by the doping
elements and to the colored centers present in the matrices KCl and KBr are also visible
on the spectra.
The photoluminescence of the samples shows an emission bands due to radiative
electronic transitions of the rare earth elements, demonstrating that the matrices studied
can be considered as luminophores. The relatively high concentration of the doping
elements leads to a decrease in the intensity of the observed luminescence bands; this
decrease may be due to a mutual influence of the rare earth atoms incorporated in the
KCl and KBr matrices. The analysis by radio-luminescence shows intense emission
bands and shows that the elaborated materials can be used as scintillators for the
detection of X-rays.
Mots clés: chlorure de terre rare (ErCl3, CeCl3), oxyde de terre rare Lu2O3, Czochralski, DRX,
FT-IR, μ-Ramn, absorption UV-visible, photoluminescence, radio-luminescence
