STUDY OF STRUCTURAL AND SPECTRAL CHARACTERISTICS OF CRYSTAL Y3Al5O12, Al2O3 AND SrTiO3 DOPED BY 3d- OR 4f- IONS
The subject of our research is a study of the effects of various treatments on the structural and spectral characteristics of oxides (Y3Al5O12, Al2O3 and SrTiO3) belonging to the group of ionic crystals with a wide energy band gap. We have investigated the dielectric and optical characteristics of single laser crystals of Y3Al5O12 (YAG) doped by ions from the group of iron (3d-), Al2O3 single crystal and SrTiO3 crystals doped by 3d and 4f- ions. Dielectric properties of the investigated single crystals were analyzed using dielectric spectroscopy (80 kHz – 15 MHz) in a wide temperature range (50 – 400 K). The comparison of the temperature dependence of the dielectric permittivity (εr) and dielectric loss (tanδ) at different test frequencies for undoped and doped crystals was performed. The optical properties were studied on the basis of the absorption spectra in the UV-Vis region. The experiment results showed that presence of 3d dopants in YAG crystal caused a displacement of the absorption edge and appearance of characteristic peaks. The differences observed in the absorption spectra were probably the result of the 3d ions incorporation on two possible symmetrically different positionings of aluminum ions –tetrahedrical and octahedrical– in the YAG crystal lattice. The dielectric spectroscopy measurements for samples of SrTiO3 doped by 4f ions showed anomalous behaviors of the dielectric permittivity at temperatures around the temperature of the structural phase transition 105 K.
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