Room-temperature line emission at 1.2 μm from chromium-activated barium ortho-titanate

• Published in: Journal of luminescence 1994-02, Vol.59 (1), p.113-124
• Main Authors: Pappalardo, R.G., Peters, T.E., Miniscalco, W.J., Alexander, E.J.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Infrared and raman spectra and scattering; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other nonmetallic inorganics; Other nonmetals; Physics; Visible and ultraviolet spectra
• ISSN: 0022-2313; 1872-7883
• DOI: 10.1016/0022-2313(94)90028-0

A Cr-activated material, Ba 2TiO 4:0.1%Cr, exhibits at room temperature line emission at ∼1.2 μm, with an exponential decay constant of ≈80 μs. At low temperatures the decay constant increases to ≈240 μs, and an intensity redistribution takes place within the main emission doublet, with the high-energy component of the doublet drastically losing intensity. At higher Cr formulations (0.5% and 1%) line emission and band emission are simultaneously present. An interesting discontinuous change is noted in the emission/excitation properties at these higher Cr formulations, namely at 1%Cr a new set of emission lines, to the high-energy side of the original set, appears at low temperatures, and this is accompanied by marked changes in the excitation spectra. The Ba 2TiO 4:Cr materials were post-fired in nitrogen, in an attempt to induce the formation of visible-emitting Cr 3+ centers. Instead, this post firing tended to enhance the band-emission components in the ∼1.3 μm region. The line emission is attributed to Cr 4+ in four-coordinated sites. In the simple Tanabe-Sugano formalism this implies the choice of Dq/B values exceeding those reported in the literature for Cr-activated försterite. For Dq/B≈2 the lowest excited level is 1E and the observed line emission is assigned to the inter-system transition 1E(e 2)→ 3A 2(e 2).