title: Up-conversion luminescence in Yb(3+)-Er(3+)Tm(3+) co-doped Al(2)O(3)-TiO(2) nano-composites.
abstract: The sol gel method was used to prepare rare-earths (Yb3+-Er3+and Yb3+-Tm3+) co-doped Al2O3-TiO2nano-composite powder phosphors and their up-conversion luminescence properties were investigated. Mixed oxides of titania (TiO2) rutile phase and an early stage crystallization of alumina (Al2O3) phase were confirmed from the X-ray diffraction data with the average crystallite size of ∼36nm. The rutile phase TiO2was further confirmed by selected area diffraction analysis of the composites. Microscopy analysis showed interesting rod-like morphologies with rough surfaces indicating that a spherulitic growth process took place during the crystal growth. Photoluminescence characterization of the phosphors was carried out under near infra-red excitation at 980nm and the prominent emission bands were observed in the visible region at 523, 548 and 658nm for the Yb3+-Er3+co-doped systems. Emission in bands extending from the visible to near infra-red regions were observed at 480, 650, 693 and 800nm for the Yb3+-Tm3+co-doped systems. These upconverted emissions and energy transfer mechanisms taking place are discussed in detail.
authors.affiliation: Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA 9300, South Africa.
authors.forename: Teboho Patrick
authors.initials: TP
authors.lastname: Mokoena
authors.affiliation: Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA 9300, South Africa.
authors.forename: Ella Cebisa
authors.initials: EC
authors.lastname: Linganiso
authors.affiliation: Photovoltaic Laboratory, Centre for Energy Studies, Indian Institute of Technology Delhi, New Delhi 110016, India.
authors.forename: Vinod
authors.initials: V
authors.lastname: Kumar
authors.affiliation: Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA 9300, South Africa.
authors.forename: Hendrik C
authors.initials: HC
authors.lastname: Swart
authors.affiliation: Materials Architecturing Research Centre, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 02792, Republic of Korea.
authors.forename: So-Hye
authors.initials: SH
authors.lastname: Cho
authors.affiliation: School of Physics, University of the Witwatersrand, Private Bag X3, Wits, 2050, South Africa. Electronic address: ntwaeab@gmail.com.
authors.forename: Odireleng Martin
authors.initials: OM
authors.lastname: Ntwaeaborwa
keywords: Alumina-titania nano-composites; Sol-gel; Up-conversion mechanism; Visible to NIR emissions