Akademik Veri Yönetim Sistemi
Tezin Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Türkiye
Tezin Onay Tarihi: 2016
Tezin Dili: İngilizce
Öğrenci: Metehan Severoğlu
Eş Danışman: AYŞEN YILMAZ, OKAN ESENTÜRK
Özet:LnBO3 are notable host materials to doped with Rare Earth Element (REE) to achieve strong luminescence. Therefore, it attracts great attention of scientist for many decades with promising applications in many field such as affordable Light Emitting diode (LED) devices. This research covers the synthesis of undoped lanthanum, gadolinium, and yttrium orthoborates and dysprosium, terbium and samarium ions doped LnBO3 (Ln: La, Gd, Y) by microwave assisted solid state synthesis method to investigate the effect of changing concentration and identity of ions on their photoluminescence properties. Microwave assisted solid state synthesis method has various advantages such as reducing energy consumption with decreasing heating duration and producing fine powders. The samples were synthesized by heating mixtures of precursor solid reactants in microwave oven at 1200 W for ten minutes and heating them at 950° C for 2 hours in muffle furnace. For characterization of powder samples X-ray diffraction were used. The morphological properties of undoped and rare earth ions doped the samples were examined by Scanning Electron Microscope (SEM). Moreover, Attenuated Total Reflection (ATR) spectrometry were done to identify vibrational modes of anionic groups. Far-IR spectrometry were employed for detecting low frequency modes. Fluorescence spectroscopy were employed for finding the luminescence characteristics of products. The XRD patterns demonstrate that undoped and doped LnBO3 powder samples were synthesized successfully with microwave assisted solid state method. From the XRD patterns, it is observed that added doping materials do not disturb the hosts’ structure. SEM images of undoped and doped LnBO3 powders show a fine particle with regular morphology. As results, doping with Dy3+, Sm3+, Tb3+ ions did not affect the crystallinity and morphology of LnBO3. ATR results demonstrated that the presence of planar BO33- units in LaBO3 whereas tetrahedral B3O99- ring containing planar BO33- and tetrahedral BO45- units in GdBO3 and YBO3. Far-IR results illustrate low frequency vibrational modes of LnBO3. The differences in the observed vibrational modes of doped and undoped LnBO3 help on identification of doping characteristics as interstitial or substitutional. Luminescence studies showed that 5.30% Dy doped LaBO3 samples gives rise to the most intensive emission among all the samples prepared. International Commission on Illumination (CIE) studies show that Dy doped LnBO3 samples give pale yellow, Sm doped LnBO3 samples give orange color and Tb doped LnBO3 samples give green color.