Respondent
Theme
Structural chemistry of silicides, germanides and stannides of alkali and rare earth metals
Defence Date
Annotation
The thesis is devoted to the study of general regularities and crystal chemistry
characteristics of silicides, germanides and stannides of alkali and rare earth metals. As a
result of the research isothermal sections of nine ternary systems of La, Tb, Dy}-Li-Si,
{La, Nd}-Li-Ge, {Y, Ce, Eu, Tb}-Li-Sn and parts of thirteen phase diagrams of quaternary
systems of {La, Sm}-Li-Co-Si, Tm-Li-Со-Sn, La-Li-Ni-Si, {La, Pr, Nd}-Li-Ni-Ge, {La,
Tb, Dy, Ho, Er, Tm}-Li-Ni-Sn. 131 ternary and quaternary compounds were synthesized
for the first time. For 122 of these intermetallic compounds crystal structures were fully
defined. They crystallize in 23 known structural types. In the studied and related to them
systems was confirmed the existence of 93 binary and ternary compounds. Parameters of
crystal lattices at different temperatures for 65 of these were specified by X-ray methods.
Formation of 5 new structural types was found: La2 LiGe4 Si2 , Tm2,2Co6Sn20,
TmLi2Co6Sn20, Ce2Li0,39Ni1,61Si2 and La2LiAlGe2. For all analyzed ternary systems the same
pattern was observed, the vast majority of the ternary phase is in areas of limited from 30
to 60 at.% content of elements of p-block. It was discovered that increasing the number of components in the system does not increase the number of intermetallic compounds but
causes more prevalent the formation of solid solutions.
Intermetallic compounds were systematized for the first time basing on the concept
of electronic localization as a reason for the formation of chemical bonds. Relying on the
crystallochemistry analysis it was found that most of the synthesized compounds through
primary metallic bonds have other bonds, for example covalent or ionic. It was established
that the ionization of atoms can lead to the formation of structures with monatomic
cations/anions, polyatomic polycations/polyanions, and structures with layers of 2D and
3D polycations/polyanions. For some of the compounds general process of lithiation,
parameters of hydrogen sorbtion and discharge capacity were studied. Some of the
synthesized compounds are recommended to use as anode materials for metal hydride
power sources with high energy capacitance, absorbent materials for hydrogen storage,
electrode materials for lithium-ion batteries.
Key words: intermetallic compounds, alkali metals, rare earth metals, phase
diagram, isothermal section, crystal structure, coordination of atoms, physical and
chemical properties.