3d-Transition metal (TM) ion-doped glasses exhibit interesting
spectroscopic and electrical properties and gain promising technological
applications in solid state lasers, phosphors, solar energy
converters, plasma display panels, electronic and optical devices
[1–6]. In comparison with bulk crystalline hosts, glasses have the
advantages of easy fabrication, low cost, good optical, mechanical
properties and chemical stabilities [7]. Silicate glass plays a
significant role in various technically-orientated glass applications.
Borosilicate glasses have mixed network formers and combine the
advantages of the stability of silicate glass and the higher TM ion
solubility of borate glass without producing heavy concentration
quenching, and thus are promising candidates for good TM ion
hosts to develop highly efficient luminescence materials [8–10].
A recent development in this research area concerning the spectroscopic
studies of collective 3d-TM ions (from Ti to Cu) in various
host glasses, as investigated by Abdelghany and co-workers, has
indicated that that barium borate, and lead silicate glasses favor
the presence of TM ions in their high valence states or tetrahedral
coordination while the high P2O5 content in the host glasses promotes
low oxidation states or octahedral coordination [11–15].
The first member of the 3d-TM ions, titanium, has been attracting
increasing interest in its optical properties [16–18] because the
addition of titanium dioxide can increase the refractive index,
density, transformation temperature and chemical durability of
the glass, thereby extending its applications. Ti4+ ions have demonstrated
fivefold coordination in a TiO2ANaO2ASiO2 glass and sixcoordinate
coordination when the TiO2 content was larger than
10 mol% [19]. The TiO2-containing SrOAB2O3 glasses are found to
favor the presence of titanium ions mostly as tetravalent Ti4+ ions,
which show a UV absorption band [20]. On the other hand, Ti3+
environments in silicate glasses have been attributed to one
six-coordinated Ti3+ and two five-coordinated Ti3+ ions (square
pyramid and trigonal bi-pyramid, respectively) after reduction of
Ti4+ ions under beta irradiation [21]. Furthermore, Ghoneim et al.
recently demonstrated that distorted octahedral Ti3+ ions give
two visible absorption bands at about 550–580 nm and 680–
740 nm due to the respective transitions 2
B2g ? 2
B1g and 2
B2g ? 2
A1g in TiO2-containing lithium phosphate, lead phosphate
and zinc phosphate glasses