Hrvatska Akademija Znanosti i Umjetnosti

Hrvatska Kristalografska Zajednica

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Croatian Academy of Sciences and Arts

Croatian Crystallographic Association

7.1  Laboratory of Solid State Chemistry, Rudjer Bošković Institute, Zagreb

Želimir Blažina

  Starting with the late fifties of the past century, crystallography has a long tradition in the Laboratory for Solid State Chemistry (former Laboratory for High Temperature Materials) of the Rudjer Bošković Institute in Zagreb. Numerous techniques used for preparation and identification of crystalline materials have been developed and applied since then. Single crystal growth of Rochelle salt, influence of impurities on its crystal morphology, incorporation of impurities into the crystal and their effect on (di)electric properties were studied (M. Topić). About that time float zone crystal growth was used for preparation of high purity single crystals of germanium and silicon.  Some year later uranium and thorium ternary silicides and germanides containing transition metals were prepared, and their crystal structures were studied by X-ray powder diffraction. Previously unknown crystal structure type of the composition ThM₂Si₂ was determined (Z. Ban and M. Sikirica). X-ray powder diffraction and neutron diffraction methods were used to study the irreversibly phase transition of cubic thorium carbohydride (carbodeuteride) ThCH₂(D) into its hexagonal modification which was observed at 380^oC (M. Makovec). The discovery of fcc allotropic modification of uranium and its stabilisation by small amounts of non-metals (S, N, O, Se, Te) was also studied using neutron and X-ray powder diffraction methods. (M. Tudja). Chemical vapour transport technique was used for preparation of ternary uranium compounds of the composition UNTe, UNAs and UAsSb.  Their crystal structure was determined by X-ray powder diffraction; it was found that they crystallised in the tetragonal structure of the PbFCl type (Z. Despotović, R. Trojko). The technique of isothermal transport reactions (with or without initial contact) between metals in molten alkali chloride mixtures was developed, and applied to the systems containing combinations of Cu, Ni, Ag, Pt, Cr and Fe metals (M. Paljević). The ongoing intensive research, preparation, stability studies and crystal structure determination of multicomponent intermetallic compounds started with the early seventies of the past century. A systematic study of phase equilibrium was carried out for selected rare earth - iridium systems. Substitution of one or both components in binary intermetallic compounds of the general composition AB₂ and AB₅ with other metals or metalloids, has been used as a standard method for tailoring materials suitable for hydrogen storage purposes. Thermodynamic properties of the corresponding intermetallic compound – hydrogen systems were determined from the pressure composition isotherms (PCI) at various temperatures obtained by tensimetric methods (Ž. Blažina, A. Drašner, B. Šorgić).  So far the crystal structures of about fifty intermetallic compounds have been quoted in Pearson’s Handbook of Lattice Spacings and Structures of Metals, in the Powder Diffraction File Search Manual of Inorganic Compounds and in Metal Hydride Reference List of Sandia National Laboratories. The most recent intensive investigations are theoretical studies of intermetallic compounds based on electronic structure calculations. The standard calculation methods within the density functional theory (DFT) are used. The aim is to obtain theoretical parameters which will elucidate the fundamental knowledge of thermodynamic, electrical, chemical and magnetic structure and properties of this class of materials (G.Miletić).

* on the picture: ThM₂Ge₂ structure, Acta Cryst 18 (1965) 584

7.2  The Glass Laboratory,  Rudjer Bošković Institute, Zagreb

Andrea Moguš-Milanković

   The Glass Laboratory at Rudjer Bošković Institute (Andrea Moguš-Milanković, Ana Šantić, Luka Pavić) employs crystallography in conjunction with electrical characterization to study relationship between the composition, structural and electrical properties of various materials. Principal techniques in electrical characterization include the Impedance Spectroscopy (IS) and Thermally Stimulated Polarisation Current (TSDC/TSPC) measurements combined with Raman spectroscopy and XRD techniques. Research programs cover transition metal oxide glasses, bioactive materials and ionic liquids composites. Special interest is focused on the mechanism of crystallization of amorphous systems (phosphate, silicate, bioactive glasses), determination of crystalline phases, particle sizes and volume fractions and their influence on the electrical properties. Part of the research considers a surface activity of the electrically polarised bioactive materials.

Easy conductive pathways in partially crystallized 40Fe₂O₃-60P₂O₅ (mol%) glass through a) glass matrix and b) grain boundaries