Emission characteristics of ZnO-TiO₂ upconversion scintillator containing Er³⁺ and Yb³⁺ using MOD method

Abstract

The metal organic decomposition (MOD) method enables the coating of any oxide material via atmospheric baking of a solution applied to a substrate and enables the fabrication of thin films via simple processes such as using spin coaters. We used titanium oxide, zinc oxide (ZnO), ytterbium oxide, and erbium oxide as MOD solutions. We mixed Ti, Zn, Yb, and Er at arbitrary mixing ratios, applied them on substrates, and then heated them at 1000°C for 4 h under atmosphere. We found that the maximum value for luminance of the upconversion (UC) scintillator can be obtained with mixture ratios of the base material Ti : Zn = 1 : 1 and Yb : Er additives = 0.06 : 0.02. When Yb : Er ratios were from 1:3 to 3:1, a 550 nm green light and 650 nm red light were observed. Moreover, by varying the mixture ratio of RE elements, the UC emission intensity can be controlled. As a result, the UC scintillators produced via the MOD method show the potential for use as multi-functional materials in displays and solid-state illumination.

Nanoscale mapping of ZnO–TiO2 up-conversion phosphor containing Yb3+ and Er3+

“…As the content of Yb is reduced, the emission intensities changed at 555 nm ( 4 S 3/2 → 4 I 15/2 ) and 672 nm ( 4 F 9/2 → 4 I 15/2 ). Our past study examined the energy-transfer process in detail [31]. In Yb and Er doped samples, the emission intensities of the green component at 555 nm ( 4 S 3/2 → 4 I 15/2 ) are close to each other.…”

“…Yb and Er oxides were adopted as doping materials. In reference to Luitel et al [30], our previous work identified the best molar ratio for this UC phosphor as Ti/Zn/Yb/Er=1/1/0.06/0.02 is best [31]. However, to increase the luminescence efficiency, each element of the metal oxide must be analyzed in more detail.…”

“…The molar ratio of the host materials was fixed at Ti/Zn=1/1, and the mixing ratio of the RE elements was varied. For the doping materials, we initially used the best ratio of RE elements (Yb, Er) from a past study, i.e., Ti/Zn/Yb/Er=1/1/ 0.06/0.02 [31], and varied the RE molar ratio around that to identify the optimum condition.…”