Untitled

Optical absorption and fluorescent behaviour of titanium ions in silicate glasses

“…So the entire amount of titanium is present in the glass in its tetravalent state. In order to marking the UV-bands for Ti 4+ ion having high intensities as found earlier to be of the order of around 10 3 g-mol/l/cm of a 3Na 2 O⋅7SiO 2 in ultraviolet region (Singh and Singh 2001), the concentration of TiO 2 was kept quite low (0⋅05-0⋅10 wt%), but the absorption of the UV-radiation even in thinner glass samples at λ max at ~ 310 nm was found to be infinite showing zero transmission in the curve (figure 1). At this stage it is mentioned that Ti 4+ ion would be a good substitute for Ce 4+ ion for producing UV absorbing glasses for commercial applications as titania being cheaper than ceria.…”

“…These authors suggested the mechanism of charge transfer from ligand to central metal ion in the binary sodium silicate glass based on the values of intensity of the bands. Further, they had also reported the appearance of UV-bands in the glass due to Ce 4+ , V 5+ and Cu + ions and attributed the bands to ligand to metal (L → M) charge transfer in V 5+ ion and Ce 4+ ion and metal to ligand to metal (M → L → M) cooperative charge transfer in the case of Cu + ions (Cu + → O → Cu 2+ ), respectively in the glass (Singh et al 1986;Singh and Singh 2001). Steele and Douglas (1965) suggested that in silicate glasses on the one hand ferrous ion is responsible for charge transfer band in UV region in between 200 and 230 nm with an intensity of 3 × 10 3 g mol/l/cm, while on the other hand, in silicate and borate glasses ferric ion has strong charge transfer band with molar extinction coefficient of 7 × 10 3 g mol/l/cm centred at its wavelength maxima at around 230 nm in ultraviolet region.…”

“…In normal melting conditions titanium can be present in basic silicate glasses in air as furnace atmosphere in the form of Ti 4+ ion whereas under strongly reducing conditions it can exist as Ti 3+ ion (Kumar 1959;Bamford 1962Bamford , 1977Bates 1962;Weyl 1967;Lee and Bruckner 1982;Paul 1982;Singh and Singh 2001). Several other systematic investigations have been carried out on optical absorption characteristics of glasses containing transition metal ions as well as their role as redox with particular reference to 3d transition metal ions viz.…”

“…Cu + /Cu 2+ , Fe 2+ /Fe 3+ , Mn 2+ / Mn 3+ , V 3+ /V 5+ and Cr 3+ /Cr 6+ pairs, but information on the mechanism of charge transfer process resulting in the absorption bands due to Ti 4+ ion in commercial type of silicate glasses had been lacking over past several years (Johnston 1964;Paul and Douglas 1965;Banerjee and Paul 1974;Singh et al 1978a,b;Duram and Fernandes Navarro 1985;Cable and Ziang 1989a,b;Bae and Weinberg 1991;Kumar 1992, 1995;Morinaga et al 1994;Singh and Singh 1998). However, Singh and Singh (2001) had studied the spectrochemical behaviour of charge transfer bands due to d 0 , d 5 and d 10 ions in a sodium silicate glass and reported the intensity of the bands due to Ti 4+ ion as 1⋅65 × 10 3 and 1⋅13 × 10 3 g mol/l/cm of glass at their wavelengths maxima of 250 nm and 290 nm in the glass, respectively. These authors suggested the mechanism of charge transfer from ligand to central metal ion in the binary sodium silicate glass based on the values of intensity of the bands.…”

“…In the case of iron present in the silicate glass, the mechanism of charge transfer has been suggested as exchange of electrons in between M → L → M cooperative charge transfer in the glass (Steele and Douglas 1965;Wood and Remeika 1966). Whereas in the case of sodium silicate glass containing hexavalent chromium the mechanism of charge transfer has been reported as transfer of electron from oxygen ligand to central metal ion as L → M charge transfer Singh and Singh 2001). Paul (1982) had also studied the mechanism of charge transfer with mixed cerium-titanium redox in a sodium boroalumino silicate glass and suggested that the broad charge transfer band had arisen at about 345 nm due to cooperative charge transfer within Ce 3+ -O -Ti 4+ coloured chromophore.…”