Akademik Veri Yönetim Sistemi
Tezin Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Türkiye
Tezin Onay Tarihi: 2016
Tezin Dili: İngilizce
Öğrenci: Saeed Vahed Qaramaleki
Eş Danışman: AYŞEN YILMAZ, DENİZ ÜNER
Özet:Within the scope of this research project three different rare earth elements such as Dysprosium (Dy), Terbium (Tb) and Samarium (Sm) have been doped inside two different host material namely LaBO3 and GdBO3 orthoborates. The preparation of materials were conducted at low temperature by hydrothermal synthesis method. After preparing the solution of precursors it has been placed into a well-sealed Teflon lined autoclave and maintained in 200 ˚C inside a furnace for 24 hours. The obtained powder was then washed with deionized water and dried at 80 ˚C. Structural and optical properties of as-prepared materials were investigated by using various characterization techniques. In order to study the phase composition and crystal structure of materials X-ray diffraction (XRD) method was applied. IR spectroscopy of produced materials has been implemented in an effort to investigate the vibrational modes of anionic groups. Moreover, by conducting FAR-IR spectroscopy low frequency vibrational modes such as metal-metal bonds and metal-oxygen bonds have been studied. Morphology and homogeneity of powder samples were analyzed by using scanning electronic microscopy (SEM) method. Luminescent properties of produced materials were scrutinized by fluorescence spectroscopy. Based on the results obtained through various characterization analysis, it has been found that after certain concentration, doping of rare Earth elements inside the LaBO3 orthoborates would cause serious disruption to the crystal structure of the host material .This concentrations for Dy, Tb and Sm doping are 5%, 7% and 10 % respectively. Nonetheless, when the GdBO3 was used as host material, doping with different amount of rare earth elements in the range of 2.5-15% has not resulted in remarkable change on the structure of host material. The IR analysis of synthesized materials revealed the different vibrational modes of anionic structure. Samples with LaBO3 as the host material exhibit vibrational modes which could have been assigned to trigonal planar borate structure (BO33-). On the other hand, when the GdBO3 were used as the host, IR spectroscopy has shown the characteristic absorption bands of tetrahedral ring structure of borate (B3O99-). The fluorescence spectroscopy has revealed the optimum concentration of doping for each of LaBO3 and GdBO3 doped with Dy, Tb and Sm, respectively. The optimum concentration for LaBO3 doped with Dy, Tb and Sm are 5, 7 and 5%, respectively. In the case of Dy, Tb and Sm doped GdBO3 samples the best PL performance was obtinaed with 7.5, 10 and 5% concentrations, respectively. In order to specify the perceived color of prepared materials color chromaticity coordinates of each sample have been calculated by a MATLAB coded program and photoluminescence data obtained from fluorescence spectroscopy. It has been observed that Dy doped samples give yellow color, Tb doped samples give green color and Sm doped samples give orange color.