Synthesis and Optical Property Studies of Nanocrystalline ZrO[sub 2]:Ti Long-Lasting Phosphors

Abstract

A facile synthetic route to synthesize the nanocrystalline zirconia particles via preparing polyzirconoxane with zirconium tetraalkoxide is reported, and the luminescent properties of the so-obtained ZrnormalO2:Ti nanophosphors are systematically investigated in this paper. The bluish-white photoluminescence and phosphorescence originating from the recombination of electrons trapped by anion vacancies and the holes created in the valence band, and the Ti3+ ion substituting for Zr4+ is assumed to be the luminescent center. The long afterglow from ZrnormalO2:Ti is attributed to the oxygen vacancies caused by the addition of Ti3+ ions into ZrnormalO2 host. Compared with the bulk ZrnormalO2:Ti , the nanosized phosphors exhibit a longer persistent time because of the increased surface traps due to the large surface-to-volume ratio in the nanoparticles. This long persistent process can be elucidated by a simple possible mechanism.

Studies of the phosphorescence of polycrystalline hafnia

“…The published TL studies of undoped and Ti-doped ZrO 2 have reported several peaks in the temperature range À 50 to 200 1C [11,[22][23][24][25][26][27]. While there is no complete agreement between these studies on the TL peak positions, most studies have found 3 peaks, with the strongest peak in the range 20-30 1C and weaker peaks near À 25 1C and in the range 100-130 1C.…”

“…It was proposed that the luminescent center is formed by a Ti 3 + ion that substitutes for Zr 4 + , and that sixfold O-atom coordination around Ti 3 + facilitates the formation of a V 2 À oxygen vacancy [22]. Therefore, in the more recent work it has been usually accepted that Ti is the phosphorescence activator in ZrO 2 [24,26,27]. It has been suggested that oxygen vacancies produced by Ti 3 + substitutions for Zr 4 + act as electron traps [27], and that Ti 3 + substitutions act as hole traps [22].…”

“…Therefore, in the more recent work it has been usually accepted that Ti is the phosphorescence activator in ZrO 2 [24,26,27]. It has been suggested that oxygen vacancies produced by Ti 3 + substitutions for Zr 4 + act as electron traps [27], and that Ti 3 + substitutions act as hole traps [22]. Iacconi et al [22] also proposed that the traps responsible for the TL peak at À28 1C are related to the presence of traces of tetragonal ZrO 2 within the monoclinic ZrO 2 .…”

Structure–property relationship of luminescent zirconia nanomaterials obtained by sol–gel method

“…This interpretation originated from the observation that the undoped zirconia presented the same spectroscopic behavior as with Ti doping. The earlier mechanisms for the conventional and persistent luminescence based on the presence of Ti in ZrO 2 are, however, rather qualitative [21] and do not account for e.g. the energetics in the system.…”

Persistent mechanoluminescence induced by elastic deformation of ZrO2:Ti phosphors

“…(ii) local piezoelectric field causes the detrapping of electrons from the traps, whereby the detrapped electrons move in the conduction band; (iii) some of the detrapped electrons moving in the conduction band are captured in the excited state of Ti 4 + ions, whereby excited Ti 4 + ions are produced [22][23][24][25][26][27]; (iv) subsequently, the de-excitation of the excited Ti 4 + ions gives rise to the light emission.…”