| Abstract [eng] |
The development and application of advanced materials is a very important task of today's information society. Garnet crystal structure compounds because of their specific physical and chemical properties are widely used in information technology, manufacturing of solid-state lasers and optical equipments, medical equipments and many other areas. Therefore, these materials because of their unique properties and characteristics are of high interest so far. For the first time Ce-Al-O, Pr-Al-O, Nd-Al-O, Tb-Al-O, Dy-Al-O, Ho-Al-O, Er-Al-O, Tm-Al-O, Yb-Al-O, Lu-Al-O, Y(Nd)-Al-O and Y(Sm)-Al-O acetate-nitrate-glycolate gels have been synthesized using environmentally friendly, economical and simple aqueous sol-gel method. They were used as starting materials for the synthesis of appropriate lanthanide aluminium garnets. The results of X-ray difraction analysis have indicated that single-phase terbium aluminium garnet (Tb3Al5O12), dysprosium aluminium garnet (Dy3Al5O12), holmium aluminium garnet (Ho3Al5O12), erbium aluminium garnet (Er3Al5O12), thulium aluminium garnet (Tm3Al5O12), ytterbium aluminium garnet (Yb3Al5O12) and lutetium aluminium garnet (Lu3Al5O12) have been synthesized by annealing Tb-Al-O, Dy-Al-O, Ho-Al-O, Er-Al-O, Tm-Al-O, Yb-Al-O and Lu-Al-O precursor gels for 10 hours at 1000 °C, respectively. For the first time these garnet structure compounds were synthesized using sol-gel method. Moreover, these lanthanide aluminium garnets were synthesized at relatively low sintering temperature (1000°C). It was demonstrated that cerium aluminium garnet Ce3Al5O12, praseodymium aluminium garnet Pr3Al5O12 and neodymium aluminium garnet Nd3Al5O12 are not formed using the same synthesis conditions. X-ray difraction analysis findings have indicated that synthesis products consist of: (a) cerium and aluminium oxides (CeO2 and Al2O3); (b) aluminium oxide and perovskite praseodymium and neodymium aluminates (Al2O3 and PrAlO3 or Al2O3 and NdAlO3). Neodymium substituted garnets Y3-xNdxAl5O12 have been synthesized using the same aqueous sol–gel method. The results of the X-ray difraction analysis showed that when small amounts of neodymium (x = 0.1, 0.25, 0.35, 0.5, 0.6, 0.7, 0.8) is introduced into yttrium position the single phase Y3-xNdxAl5O12 garnets have formed and yttrium aluminium garnet lattice remains unchanged. Samarium substituted garnets Y3-xSmxAl5O12 were also synthesized using sol–gel method. The results of X-ray difraction analysis showed the formation of single phase Y3-xSmxAl5O12 garnets when small amounts of samarium (x = 0.1, 0.15, 0.25, 0.5, 0.75, 1) was introduced into yttrium position. With further increasing amount of neodymium in Y3-xNdxAl5O12 (x = 1.5, 2) compounds significant amount of side neodymium perovskite aluminate (NdAlO3) phase has formed. However, when the concentration of samarium was reached the same level or even higher in Y3-xSmxAl5O12 (x = 1.5, 2, 2.5) compounds, the phase composition of synthesis products changed marginally. Only small amount of perovskite samarium aluminate (SmAlO3) phase was detected in the end products. It was found that single-phase NdAlO3 was formed during the sol-gel synthesis of mixed-metal compounds with nominal composition of Y3-xNdxAl5O12 (x = 2.5, 3) Besides, it was determined, that single phase SmAlO3 was formed only during synthesis of fully samarium substituted Sm3Al5O12 garnet. It was demonstrated that infrared spectroscopy is very effective method to determine compounds having garnet crystal structure. An interval from 950 to 450 cm-1 of IR spectrum can be successfully used as fingerprint to identify the formation of garnet crystal structure compounds. The scanning electron microscopical characterization showed that the surface of majority of synthesized lanthanide aluminium garnets is composed of plate-like crystallites with various particle size (from several micrometers to 20 mm). |
