Energy transfer processes in the solid solutions of complex oxides
Kuupäev
2017-05-12
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Abstrakt
Käesoleva doktoritöö peamiseks eesmärgiks oli näidata kuidas muutused boraatide, fosfaatide ja vanadaatide segukristallide koostises mõjutavad nende struktuurseid, elektroonseid ja optilisi omadusi (erilise tähelepanu all olid lisandamata ja Eu3+ või Ce3+ ioonidega lisandatud LuxY1-xBO3, LuxY1-xPO4, LuxY1-xVO4 segukristallid). Eelnevalt mainitud materjalid on leidnud laialdast kasutust valgusallikate ja stsintillatsioonseadmete (valgussähvatustsseadmete) rakendustes. Sama oksüdatsiooni astmega positiivse laenguga iooni asendamine vanadaatide ja fosfaatide segukristallides ei muuda nende struktuuri, kuid mõjutab nende materjalide erinevaid füüsikalisi omadusi. Näidati, et koos järk-järgulise ühe katiooni (Lu) asendamisega teisega (Y) muutuvad sellistes segukristallides küll lineaarselt struktuuriparameetrid kuid mittelineaarselt kiirguse intensiivsus. Maksimaalne kiirguse intensiivsus LuxY1-xVO4 segukristallides saavutati juhul kui x = 0.7. Sellist nähtust saab selgitada muutustega laengukandjate vaba tee pikkuses, mis on omakorda põhjustatud elektronstruktuuri muutustest. Optimaalne koostis, mis selgitati välja doktoritöö raames, võib viia fosfooride ja stsintillaatormaterjalide jõudluse parendamiseni. Lisaks täiendavad antud doktoritöös välja pakutud tulemuste selgitused mikrotaseme baasteadmisi mateeria ja valguse interaktsioonist.
The main goal of the thesis was set to demonstrate how the modification of the crystal composition affects the structural, electronic and optical properties of a series of borate, phosphate and vanadate crystals (LuxY1-xBO3, LuxY1-xPO4, LuxY1-xVO4, undoped and doped with Eu3+ or Ce3+). The chosen systems are widely used for lighting and scintillating applications. The isovalent cation substitution in the vanadates and the phosphates does not change the structure, but produces pronounced influence on the wide range of their physical properties. In particular, it was demonstrated that the gradual substitution of one cation (Lu) by another (Y) is accompanied by the linear variation of the structural parameters and, what is more important, by a non-linear variation of the emission intensity in such mixed compounds. The maximum emission intensity in the LuxY1-xVO4 system is realized when x=0.7. Such a phenomenon is explained by modification of the charge carriers free path that is caused by changes in the electronic structure. The optimal composition determined in the thesis can lead to improved performance of the phosphors and scintillators based on these materials. In addition, explanation of the observed results suggested in the thesis contributed to the basic understanding of processes of interaction of light with matter at the microscopic scale.
The main goal of the thesis was set to demonstrate how the modification of the crystal composition affects the structural, electronic and optical properties of a series of borate, phosphate and vanadate crystals (LuxY1-xBO3, LuxY1-xPO4, LuxY1-xVO4, undoped and doped with Eu3+ or Ce3+). The chosen systems are widely used for lighting and scintillating applications. The isovalent cation substitution in the vanadates and the phosphates does not change the structure, but produces pronounced influence on the wide range of their physical properties. In particular, it was demonstrated that the gradual substitution of one cation (Lu) by another (Y) is accompanied by the linear variation of the structural parameters and, what is more important, by a non-linear variation of the emission intensity in such mixed compounds. The maximum emission intensity in the LuxY1-xVO4 system is realized when x=0.7. Such a phenomenon is explained by modification of the charge carriers free path that is caused by changes in the electronic structure. The optimal composition determined in the thesis can lead to improved performance of the phosphors and scintillators based on these materials. In addition, explanation of the observed results suggested in the thesis contributed to the basic understanding of processes of interaction of light with matter at the microscopic scale.
Kirjeldus
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Märksõnad
oksiidid, tahked lahused, kristallid, energiaülekanne, füüsikalised omadused, luminestsents, oxides, solid solutions, crystals, energy transfer, physical properties, luminescence