Sinteze, optička i strukturna svojstva luminiscentnih prahova na bazi gadolinijum-vandata dopiranog jonima retkih zemalja

Abstract

Glavni cilj istrаživаnjа u okviru ove doktorske disertаcije bio je da se rаzviju metode i optimizuju pаrаmetri sinteza koje su pogodne za dobijanje neorgаnskih luminescentnih prаhovа nа bаzi gаdolinijum-vаnаdаtа (GdVO4) dopirаnog jonimа retkih zemаljа i ispitaju strukturna, morfološka i optička svojstаvа dobijenih prаhovа. Poslednjih nekoliko godinа sve se više pаžnje posvećuje proučаvаnju fosfora koji su na bazi ortovаnаdаtа. Razvoj savremenih uređaja iz oblasti optoelektronike u velikoj meri zavisi od poboljšanih karakteristika luminescentnih materijala koji se koriste za njihovu izradu. Otkriveno je da su fosfori na bazi gadolinijum-vanadata dopiranog jonima retkih zemalja jedni od neorganskih luminescentnih materijala koji najviše obećavaju, čineći prilagodljiv izvor za brojne primene. U okviru ove doktorske disertacije luminescentni prahovi na bazi gadolinijum-vanadata, GdVO4, koji su dopirani jonima retkih zemalja, dobijeni su na sledeća tri načina: metodom reakcije u čvrstoj fazi, metodom hemijske precipitacije iz rastvora i metodom inverznih micela. Ovim metodama su sintetisani sledeći luminescentni prahovi: GdVO4:Tm3+, GdVO4:Tm3+/Yb3+, GdVO4:Er3+/Yb3+, GdVO4:Ho3+/Yb3+, GdVO4:Er3+/Yb3+/Li+, GdVO4:Ho3+/Yb3+/Li+, GdVO4:Tm3+/Er3+/Ho3+/Yb3+, ispitivan je njihov fazni sastav i struktura, kao i uticaj postupka sinteze na njihovu morfologiju. Takođe, u cilju proučavanja i poređenja optičkih svojstava (Stoksove i anti-Stoksove emisije) ovih sistema, detaljno je proučavano i prisustvo različitih kombinacija dopanata i ko-dopanata, kao i njihov stehiometrijski odnos. Za neke sisteme optička svojstva su merena u funkciji temperature u cilju određivanja potencijalne primene materijala u termometriji. Rendgeno-strukturna analiza svih dobijenih materijala pokazala je dobru kristaliničnost i dobijanje odgovarajuće, čiste faze sintetisanih prahova. Svi sistemi su dali čistu tetragonalnu fazu cirkonatnog tipa. Morfologija prahova snimana je na transmisionom i skenirajućem elektronskom mikroskopu u kombinaciji sa energetskom disperzionom analizom X-zraka. Utvrđeno je da se metodom reakcije u čvrstoj fazi dobijaju deformisane (nepravilne) sferne čestice prosečnog prečnika od 1,4 μm do 8,4 μm. Ko-dopiranjem ovih sistema Li+ jonima veličina kristalita raste do 90 nm za bilo koju koncentraciju Li+...

The main goal of this PhD thesis was the optimization of parameters and development of the corresponding method for synthesis inorganic luminescent powders based on the rare earth ions doped gadolinium vanadate (GdVO4). The obtained materials were characterized and structural, morphological and optical properties were studied. In the last years, more attention was paid to the study of phosphors based on orthovanadate. The development of modern devices in the field of optoelectronics depends on the improved characteristics of the luminescent materials which have been used to make them. It has been found that the phosphors based on rare earth ions doped gadolinium-vanadate are inorganic luminescent materials that are the most promising, making a customizable resource for numerous applications. In this PhD thesis luminescent powders based on the rare earth ions doped gadolinium vanadate (GdVO4) materials were synthesized by three different techniques: solid state reaction, chemical precipitation from solution and inverse micelles method. The GdVO4: Tm3+, GdVO4: Tm3+/Yb3+, GdVO4: Er3+/Yb3+, GdVO4: Ho3+/Yb3+, GdVO4: Er3+/Yb3+/Li+, GdVO4: Ho3+/Yb3+/Li+ and GdVO4: Tm3+/Er3+/Ho3+/Yb3+ systems were synthesized and characterized. The phase compositions and structure, morphologies and optical properties were investigated. In order to compare the optical properties (Stokes and anti-Stokes emissions) of obtained systems, effects and presence of different combinations of dopants and co-dopants, as well as their stoichiometric ratio were studied in details. In order to determine the potential application the systems in the thermometry their optical properties were measured as a function of temperature. XRD analysis suggests that obtained materials crystallize in the tetragonal structure without any impurities and with good crystallinity. The morphologies of the powders were recorded by transmission and scanning electron microscopes in combination with an energy dispersive analysis of X-rays. It was found that deformed (irregular) spherical particles in the range from 1.4 to about 8.4 micrometers were obtained by solid state reaction. The calculated crystallite size for these particles is about 60 nm, while in Li+ co-doped systems this size increases up to 90 nm for any concentration of Li + ions...