‘Tracers’ are bullets that emit light at the backside so that the shooter can see the trajectory of their flight. These light-emitting bullets allow snipers to hit targets faster and more accurately. Conventional tracers are all combustion type which use the heat generated upon ignition. However, the conventional tracer has a fire risk at the impact site due to the residual flame and has a by-product that can contaminate the inside of the gun and lead to firearm failure. To resolve these problems, it is necessary to develop non-combustion-type tracers that can convert heat to luminance, so-called ‘thermoluminescence (TL)’. Here, we highly improve the thermoluminescence properties of MgB4O7 through co-doping of Dy3++Ce3+ and Dy3++Na+. The presence of doping materials (Dy3+, Ce3+, Na+) was confirmed by XPS (X-ray photoelectron spectroscopy). The as-synthesized co-doped MgB4O7 was irradiated with a specific radiation dose and heated to 500 °C under dark conditions. Different thermoluminescence characteristics were exhibited depending on the type or amounts of doping elements, and the highest luminance of 370 cd/m2 was obtained when Dy 10 % and Na 5 % were co-doped.

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.

MgB2 bulk superconductors are synthesized by the solid state reaction of (MgB4+xMg) precursors withexcessive Mg compositions (x=1.0, 1.4, 2.0 and 2.4). The MgB4 precursors are synthesized using (Mg+B) powders. Thesecondary phases (MgB4 and MgO) present in the synthesized MgB4 are removed by HNO3 leaching. It is found thatthe formation reaction of MgB2 is accelerated when Mg excessive compositions are used. The magnetization curves ofMg1+xB2 samples show that the transition from the normal state to the superconducting state of the Mg excessive sam-ples with x=0.5 and x=0.7 are sharper than that of MgB2. The highest Jc-B curve at 5 K and 20 K is achieved forx=0.5. Further addition of Mg decreases the Jc owing to the formation of more pores in the MgB2 matrix and smallervolume fraction of MgB2.

MgB4O7 열형광체의 활성체는 란탄계 금속인 Tb, Tm, Dy, La, Ho 및 Nd를 첨가하여 580˚C의 Ar 분위기에서 2시간동안 소결하여 제작하였다. 활성화에너지와 glow 곡선의 주 Peak의 세기는 peak shape법과 초기상승법의 두방법에 의해 결정했으며, 최적활성에너지는 0.76±0.02eV(Tm 첨가시), 0.94±0.03eV(Tm 첨가시) 및 0.72±0.02eV(Dy 첨가시)였다. 이들 열형광체들은 저 에너지 X-선에 대해 매우 높은 감도를 나타냈으므로 방사선 센서 소자로 개발하기 위한 기초자료가 될 것으로 생각된다.