Visible emission spectra of thermographic phosphors under x-ray excitation

Abstract

Thermographic phosphors have been employed for temperature sensing in challenging environments, such as on surfaces or within solid samples exposed to dynamic heating, because of the high temporal and spatial resolution that can be achieved using this approach. Typically, UV light sources are employed to induce temperature-sensitive spectral responses from the phosphors. However, it would be beneficial to explore x-rays as an alternate excitation source to facilitate simultaneous x-ray imaging of material deformation and temperature of heated samples and to reduce UV absorption within solid samples being investigated. The phosphors BaMgAl10O17:Eu (BAM), Y2SiO5:Ce, YAG:Dy, La2O2S:Eu, ZnGa2O4:Mn, Mg3F2GeO4:Mn, Gd2O2S:Tb, and ZnO were excited in this study using incident synchrotron x-ray radiation. These materials were chosen to include conventional thermographic phosphors as well as x-ray scintillators (with crossover between these two categories). X-ray-induced thermographic behavior was explored through the measurement of visible spectral response with varying temperature. The incident x-rays were observed to excite the same electronic energy level transitions in these phosphors as UV excitation. Similar shifts in the spectral response of BAM, Y2SiO5:Ce, YAG:Dy, La2O2S:Eu, ZnGa2O4:Mn, Mg3F2GeO4:Mn, and Gd2O2S:Tb were observed when compared to their response to UV excitation found in literature. Some phosphors were observed to thermally quench in the temperature ranges tested here, while the response from others did not rise above background noise levels. This may be attributed to the increased probability of non-radiative energy release from these phosphors due to the high energy of the incident x-rays. These results indicate that x-rays can serve as a viable excitation source for phosphor thermometry.

Fabrication and Microstructure of Gd2O2S:Tb Scintillation Ceramics from Water-bath Synthesized Nano-powders: Influence of H2SO4/Gd2O3 Molar Ratio

“…While, the Gd2O2S-based phosphors have attracted considerable attention for decades [11][12][13][14] . For instance, Terbium doped gadolinium oxysulfide (Gd2O2S:Tb) phosphor exhibits intensive green emission and high luminous efficiency [15][16] , which makes it widely used for display purposes in TV screens, cathode ray tubes, and X-ray intensifying screens [17][18][19][20][21] . The Gd2O2S:Tb, applied for scintillation screens, mainly includes powder and ceramic scintillators [22][23][24] .…”

A summary of new developments in phosphor thermometry

“…This highlights the need for a thorough characterisation of the phosphor in the actual experimental setup before application, but may also open new pathways for thermometry. Westphal et al investigate the possibility to excite thermographic phosphors with x-rays instead of the typical UV excitation source [11]. Already, some known thermographic phosphors such as G 2 O 2 S:Tb 3+ and CdWO 4 are also used commercially as scintillators, converting x-ray or gamma ray excitation into visible luminescence to be easily detected for medical imaging.…”