Speaker: Nikolay N. Kuzmin, Junior Researcher of the Fourier Spectroscopy Laboratory, MIPT Ph.D. candidate.
Topic: Synthesis and spectroscopic study of rare earth gallium and chromium borates with hantite structure (report on the materials of the dissertation for the degree of candidate of physical and mathematical sciences in the specialty 1.3.6. Optics, planned for defense in the dissertation council of ISAN).
Scientific supervisor: Ph.D. (Physics and Mathematics) Boldyrev K.N. (ISAN).
Scientific consultant: Dr. Sc. (Chemistry) Maltsev V.V. (Moscow State University).
Objective of the work: study of synthesis, crystallization features and obtaining new data on the structural, optical, luminescent, magnetic properties of rare earth chromium and gallium borates with the structural type of the hantite mineral using optical, infrared (IR), luminescence spectroscopy, X-ray powder diffraction, thermal analysis.
Tasks of the work:
1. Determination of phase ratios in the triple systems R2O3 – Cr2O3 – B2O3 (R = Sm, Gd – Lu) and search for systems where the crystallization of double borates RCr3(BO3)4.
2. Study of phase ratios in pseudo-triple systems RCr3(BO3)4 – K2Mo3O10 – B2O3 (R = Tb – Ho) and pseudo-double systems RCr3(BO3)4 – K2Mo3O10 (R = Sm, Gd, Er). Determination of monophase crystallization areas and the optimal composition of the charge for the synthesis of rhombohedral modification RCr3(BO3)4.
3. Investigation of the thermal stability and melting mechanisms of double borates RCr3(BO3)4 (R = Sm, Gd – Er).
4. Obtaining IR absorption spectra of rare earth chromium borates RCr3(BO3)4 (R = Sm, Gd – Er). Finding the relationship between the obtained polymorphic modification and the conditions for synthesizing crystals.
5. Constructing energy schemes of Stark levels of rare earth ions in the paramagnetic state of borates RCr3(BO3)4 (R = Sm, Tb, Dy, Ho).
6. Investigation of magnetic phase transitions in borates RCr3(BO3)4 (R = Sm, Gd – Ho).
7. Obtaining and analyzing luminescence spectra, determining the nonlinear optical properties of rare earth gallium borates RGa3(BO3)4 (R – Nd, Sm, Tb, Dy, Ho, Er).
Main results:
1. For the first time, the regularities of phase formation in triple oxide systems R2O3 – Cr2O3 – B2O3 (R = Sm, Gd – Lu) have been determined. It has been shown that borates RCr3(BO3)4 form in systems R2O3 – Cr2O3 – B2O3 (R = Sm, Gd – Er), and for smaller rare earth ions (Tm – Lu), the stable phase is RCr(BO3)2 with the structure of the mineral dolomite.
2. For the first time, the phase formation in systems RCr3(BO3)4 – K2Mo3O10 – B2O3 (R = Tb, Dy, Ho) and RCr3(BO3)4 – K2Mo3O10 (R = Sm, Gd, Er) has been studied. The areas of monophase crystallization of RCr3(BO3)4 (R = Sm, Gd – Er) have been determined.
3. For the first time, the melting temperatures and the nature of melting of double borates RCr3(BO3)4 (R = Sm, Gd – Er) and RCr(BO3)2 (R = Ho – Er) have been determined.
4. Conditions for the crystallization of rhombohedral and monoclinic polymorphic modifications of RCr3(BO3)4 have been discovered in systems RCr3(BO3)4 – K2Mo3O10 – B2O3 and RCr3(BO3)4 – K2Mo3O10 for large RE ions – Sm and small ones – from Gd to Er.
5. For the first time, energy schemes of RE ions Stark levels in the paramagnetic state of compounds RCr3(BO3)4 (R = Sm, Tb, Dy, Ho) have been determined.
6. Magnetic phase transitions have been discovered in borates RCr3(BO3)4 and their nature has been investigated.
7. For the first time, the evaluation of RE gallium borates RGa3(BO3)4 (R – Nd, Sm, Tb, Dy, Ho, Er) nonlinear optical properties has been carried out, showing the prospects for their further research.