Bullets flying with a light from the back are called “tracers”. Tracers are ignited by the combustion gas of the propellant and emit bright light that allows the shooter to visually trace the flight path. Therefore, tracers mark the firing point for allies to assist shooters to hit target quickly and accurately. Conventional tracers are constructed with a mixture of an oxidizing agent, raw metal, and organic fuel. Upon ignition, the inside of the gun can be easily contaminated by the by-products, which can lead to firearm failure during long-term shooting. Moreover, there is a fire risk such as forest fires due to residual flames at impact site. Therefore, it is necessary to develop non-combustion type luminous material; however, this material must still use the heat generated from the propellant, so-called “thermoluminescence (TL)”. This study aims to compare the TL emission of Dy3+, La3+ and Ho3+ doped MgB4O7 phosphors prepared by solid state reaction. The crystal structures of samples were determined by X-ray diffraction and matched with the standard pattern of MgB4O7. Luminescence of various doses (200 ~ 15,000 Gy) of gamma irradiated Dy3+, La3+ and Ho3+ (at different concentrations of 5, 10, 15 and 20 %) doped MgB4O7 were recorded using a luminance/color meter. The intensity of TL yellowish (CIE x = 0.401 ~ 0.486, y = 0.410 ~ 0.488) emission became stronger as the temperature increased and the total gamma-ray dose increased.

Dy3+ and Eu3+-codoped SrWO4 phosphor thin films were deposited on sapphire substrates by radio frequency magnetron sputtering by changing the growth and thermal annealing temperatures. The results show that the structural and optical properties of the phosphor thin films depended on the growth and thermal annealing temperatures. All the phosphor thin films, irrespective of the growth or the thermal annealing temperatures, exhibited tetragonal structures with a dominant (112) diffraction peak. The thin films deposited at a growth temperature of 100 oC and a thermal annealing temperature of 650 oC showed average transmittances of 87.5% and 88.4% in the wavelength range of 500-1100 nm and band gap energy values of 4.00 and 4.20 eV, respectively. The excitation spectra of the phosphor thin films showed a broad charge transfer band that peaked at 234 nm, which is in the range of 200-270 nm. The emission spectra under ultraviolet excitation at 234 nm showed an intense emission peak at 572 nm and several weaker bands at 479, 612, 660, and 758 nm. These results suggest that the SrWO4: Dy3+, Eu3+ thin films can be used as white light emitting materials suitable for applications in display and solid-state lighting.

SrAl2O4: Eu2+ and Dy3+ phosphorescent phosphors were synthesized using the polymerized complex method. Generally, phosphorescent phosphors synthesized by conventional solid state reaction show a micro-sized particle diameter; thus, this process is restricted to applications such as phosphorescent ink and paint. However, it is possible to synthesize homogeneous multi-component powders with fine particle diameter by wet process such as the polymerized complex method. The characteristics of SrAl2O4: Eu2+ and Dy3+ powders prepared by polymerized complex method with one and two step calcination processes were comparatively analyzed. Temperatures of organic material removal and crystallization were observed through TG-DTA analysis. The crystalline phase and crystallite size of the SrAl2O4: Eu2+ and Dy3+ phosphorescent phosphors were analyzed by XRD. Microstructures and afterglow characteristics of the SrAl2O4: Eu2+ and Dy3+ phosphors were measured by SEM and spectrofluorometry, respectively.

Eu2+/Dy3+-doped Sr2MgSi2O7 powders were synthesized using a solid-state reaction method with flux (NH4Cl). Thebroad photoluminescence (PL) excitation spectra of Sr2MgSi2O7:Eu2+ were assigned to the 4f7-4f65d transition of the Eu2+ ions,showing strong intensities in the range of 375 to 425nm. A single emission band was observed at 470nm, which was the resultof two overlapping subbands at 468 and 507nm owing to Eu(I) and Eu(II) sites. The strongest emission intensity ofSr2MgSi2O7:Eu2+ was obtained at the Eu concentration of 3mol%. This concentration quenching mechanism was attributableto dipole-dipole interaction. The Ba2+ substitution for Sr2+ caused a blue-shift of the emission band; this behavior was discussedby considering the differences in ionic size and covalence between Ba2+ and Sr2+. The effects of the Eu/Dy ratios on thephosphorescence of Sr2MgSi2O7:Eu2+/Dy3+ were investigated by measuring the decay time; the longest afterglow was obtainedfor 0.01Eu2+/0.03Dy3+.

A SrAl2O4:Eu2+,Dy3+ phosphor powder with stuffed tridymite structure was synthesized by glycine-nitratecombustion method. The luminescence, formation process and microstructure of the phosphor powder were investigated bymeans of X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy (PL). The XRDpatterns show that the as-synthesized SrAl2O4:Eu2+,Dy3+ phosphor was an amorphous phase. However, a crystalline SrAl2O4phase was formed by calcining at 1200oC for 4h. From the SEM analysis, also, it was found that the as-synthesizedSrAl2O4:Eu2+,Dy3+ phosphor was in irregular porous particles of about 50µm, while the calcined phosphor was aggregated inspherical particles with radius of about 0.5µm. The emission spectrum of as-synthesized SrAl2O4:Eu2+,Dy3+ phosphor did notappear, due to the amorphous phase. However, the emission spectrum of the calcined phosphor was observed at 520nm(2.384eV); it showed green emission peaking, in the range of 450~650nm. The excitation spectrum of the SrAl2O4:Eu2+,Dy3+phosphor exhibits a maximum peak intensity at 360nm (3.44eV) in the range of 250~480nm. After the removal of the pulseXe-lamp excitation (360nm), also, the decay time for the emission spectrum was very slow, which shows the excellent long-phosphorescent property of the phosphor, although the decay time decreased exponentially.