Synthesis and structural characterization of new cesium and potassium rare-earth silicates

[P. Dabić]

99 str.

Geo-nauke / Kristalografija

Geo-sciences / Crystallography

Predmet i ciljevi naučnog istraživanja ove doktorske disertacije su sinteza i strukturna karakterizacija novih cezijumskih i kalijumskih silikata sa elementima retkih zemalja. Istraživanja su izvedena u okviru sistema SiO2–REE2O3–XF, gde REE predstavlja trovalentni katjon elementa retkih zemalja (Sc, Y, Sm, Eu, Gd, Ho, Er, Tm, Yb, Lu), dok X predstavlja jednovalentni katjon alkalnih metala (K, Cs). Rad na disertaciji bio je fokusiran na sintezu monokristala, određivanje kristalnih struktura, kao i na kristalografsko i kristalohemijsko ispitivanje sintetisanih monokristala. Monokristali su sintetisani metodom rasta kristala iz visokotemperaturnih rastvora uz upotrebu fluksa. Kristalne strukture rešene su pomoću rendgenske difrakcije na monokristalu. Kvalitet monokristala proveravan je pomoću stereomikroskopa, dok je polarizacioni mikroskop korišten za posmatranje optičkih osobina. Rendgenska difrakcija na polikristalnom materijalu služila je za proveru faznog sastava. Skenirajuća elektronska mikroskopija (SEM) dopunjena sa energetsko-disperzivnom spektroskopijom (EDS) korištena je za određivanje morfoloških karakteristika i za semikvantitativno određivanje hemijskog sastava. U toku izrade disertacije određeno je osam (8) kristalnih struktura. Kristalna struktura Cs2ErSi6O14F predstavlja novi strukturni tip, dok je struktura Cs3ScSi6O15 prvi put rešena kao modulisana struktura. Jedinjenja Cs2HoSi4O10F, Cs2ErSi4O10F i Cs2TmSi4O10F izostrukturna su sa Cs2YSi4O10F. Za jedinjenje K3EuSi2O7 određena je kristalna struktura u prostornoj grupi P63/mcm i pokazalo se da je izostrukturno sa K3REESi2O7 (REE = Nd, Sm, Gd–Yb, Y, Y0,9Dy0,1, Sm i Er). Jedinjenja K3ErSi2O7 i K3YbSi2O7 kristališu u prostornoj grupi P63/mmc i izostrukturna su sa jedinjenjima K3REESi2O7 (REE = Lu, Sc i Y).

The subject and goals of the scientific research of this doctoral dissertation are the synthesis and structural characterization of new cesium and potassium rare-earth silicates. The investigation was carried out in the SiO2–REE2O3–XF system, where REE represents a trivalent cation of a rare-earth element (Sc, Y, Sm, Eu, Gd, Ho, Er, Tm, Yb, Lu), while X represents a monovalent cation of alkali metals (K, Cs). Dissertation work was focused on the synthesis of single crystals, the determination of crystal structures, as well as on crystallographic and crystallochemical investigation. Single crystals were synthesized by high-temperature flux crystal growth. The crystal structures were solved using single-crystal X-ray diffraction. The quality of single crystals was inspected using a stereomicroscope, while a polarizing microscope was used to observe the basic optical properties. The phase composition was tested using powder X-ray diffraction. Scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS) was used for morphological and chemical characterization. Eight (8) crystal structures were determined during the work on the dissertation. The crystal structure of Cs2ErSi6O14F represents a new structural type, while the crystal structure of Cs3ScSi6O15 was solved for the first time as a modulated structure. Compounds Cs2HoSi4O10F, Cs2ErSi4O10F and Cs2TmSi4O10F are isostructural with Cs2YSi4O10F. For the compound K3EuSi2O7, the crystal structure in the space group P63/mcm was determined and it was shown to be isostructural with K3REESi2O7 (REE = Nd, Sm, Gd–Yb, Y, Y0.9Dy0.1, Sm and Er). Compounds K3ErSi2O7 and K3YbSi2O7 crystallize in the space group P63/mmc and they are isostructural with K3REESi2O7 (REE = Lu, Sc and Y) compounds.

alkalni silikati elemenata retkih zemalja, kristalna struktura, sinteza metodom fluksa, rendgenska difrakcija na monokristalu, elementi retkih zemalja

alkali rare-earth silicates; crystal structure; flux synthesis; single-crystal X-ray diffraction; rare-earth elements

548(043.3)

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