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Structural and spectroscopic characterization of Ho3+ in sol-gel silica

P. R. REJIKUMAR1, PRATHIBHA VASUDEVAN1, S. KARTHIKA1, J. GEORGE2, N. V. UNNIKRISHNAN1,*

Affiliation

  1. School of Pure &Applied Physics,Mahatma Gandhi University, Kottayam-686 560, INDIA
  2. Department of Physics, Christian college Chengannur, Kerala- 689122, INDIA

Abstract

Ho3+ doped silica glasses were prepared by the sol-gel process using tetraethyl orthosilicate (TEOS), H2O, HNO3 and Ho(NO)3.6H2O. The samples were characterized using thermo gravimetric analysis (TGA), FTIR spectra, high resolution transmission electron micrograph (HRTEM) and UV-VIS absorption spectra. Judd-Ofelt (JO) (Ω2= 4.480 x 10-20 cm2 , Ω4=2.292 x 10-20 cm2 , Ω6=2.827 x 10-20 cm2 ) parameters were derived from the optical absorption spectra. Calculated values of the J-O parameters were utilized in evaluating the various radiative parameters such as electric dipole line strengths(Sed), radiative transition probabilities (ARAD), radiative lifetimes (τRAD), fluorescence branching ratios (βR ) and the integrated absorption cross sections ( σa) for stimulated emission of Ho3+ ion. Our analysis indicates that randomly distributed three dimensional network nature of the host, clustering of Ho3+ions and the hydroxyl content are responsible for the weak fluorescence. Also asymmetry of Ho3+ in silica glass host is found to be higher than those in halide systems and lower than oxide systems.

Keywords

Glasses, sol-gel growth, Electron microscopy, FTIR spectroscopy.

Submitted at: March 31, 2010
Accepted at: May 26, 2010

Citation

P. R. REJIKUMAR, PRATHIBHA VASUDEVAN, S. KARTHIKA, J. GEORGE, N. V. UNNIKRISHNAN, Structural and spectroscopic characterization of Ho3+ in sol-gel silica, Journal of Optoelectronics and Advanced Materials Vol. 12, Iss. 5, pp. 1065-1070 (2010)