FIZIKA A 13 (2004) 2 , 53-64

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STUDY OF UP-CONVERSION LUMINESCENCE IN BaTiO3: Ho3+ NANOCRYSTALS

Y. BADRa, A. SALAHa and I. K. BATTISHAb

 aNational Institute of Laser Enhancement Sciences (NILES), Cairo University, Egypt
bNational Research Center (NRC), Department of Solid State Physics, Cairo, Egypt

Received 5 May 2003;  revised manuscript received 28 January 2004
Accepted 26 April 2004           Online 2 February 2005

Visible up-conversion emissions at 435, 545, 580, 675 and 690 nm and 437, 547, 575 and 675 nm have been obtained from BaTiO3 doped with 4 % Ho3+ ions in two different forms of the prepared samples, powder and thin film, under 808 nm laser diode excitation emissions. Combined with the energy level structure of Ho3+ ions and the kinetics of the visible emissions, the up-conversion mechanism has been analyzed and explained. The blue, green and red emissions of both samples have been attributed to the ground state-directed transition from 5F1, 5S2 and 5F5 states, respectively, which are populated through excited state absorption on 808 nm excitation. Nano-structure pure barium titanate and doped with different concentrations of Ho3+ ions in the form of powder and thin films have been prepared by so-gel technique, using barium acetate (Ba(CH3CHOO)2) and titanium isopropoxide (Ti((CH3)2CHO)4) as precursors. The thin films were prepared by spin-coating sol-gel method. The as-grown thin film and powders were found to be amorphous, which crystallized to the tetragonal phase after synthesization at 750 C in air for 30 minutes. The crystallite size of thin film and powder samples both doped with 4 % Ho3+ ions, were found to be equal to 11 and 16 nm, respectively.

PACS numbers: 81.20.Fw, 78.55.Hx, 78.30.-j
UDC 535.37, 535.375, 539.26

Keywords: BaTiO3, Ho3+ doping, sol-gel, thin film, powder, up-conversion, FT-Raman, TEM, SEM

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