Properties Of Single Crystalline Films Research Articles

Crystallization and Investigation of the Structural and Optical Properties of Ce3+-Doped Y3−xCaxAl5−ySiyO12 Single Crystalline Film Phosphors

This work is devoted to the crystallization and investigation of the optical properties of single crystalline films (SCFs) of Ce3+-doped Y3−xCaxAl5−ySiyO12 garnet, where the content of Ca2+ and Si4+ cations varied in the x = 0.13–0.52 and y = 0.065–0.5 ranges, respectively. The SCF samples were grown using the liquid phase epitaxy technique onto Y3Al5O12 substrates from the melt solution with equimolar Ca and Si content using PbO-B2O3 flux. However, the Ca and Si concentration in Y3−xCax Al5−ySiyO12:Ce SCFs is not equal: the Ca2+ content was systematically larger than that of Si4+, and the Ca2+ excess is compensated for by the Ce4+ ion formation. The absorption, scintillation, and luminescent properties of Y3−xCaxAl5−ySiyO12:Ce SCFs with different Ca/Si concentrations were investigated and compared with the sample of YAG:Ce SCF. Due to the creation of Ce4+ ions, the as-grown Y3−xCaxAl5−ySiyO12:Ce SCFs show relatively low light yield (LY) under α–particle excitation but a fast scintillation response with a decay time in the ns range. After SCF annealing in the reducing (N2 + H2) atmosphere at T > 1000 °C, the recharging of Ce4+→Ce3+ ions occurs. Furthermore, the samples annealed at 1300 °C SCF possess an LY of about 40% in comparison with the reference YAG:Ce SCF and scintillation decay kinetics much closer to that of the SCF counterpart. Due to Ca2+ and Si4+ alloying, the Ce3+ emission spectra in Y3−xCaxAl5−ySiyO12 SCFs are extended to the red range in comparison with the spectra of YAG:Ce SCF. Such an extension is caused by the Ce3+ multicenter formation at the substitutions of both Y3+ and Ca2+ dodecahedral positions in the hosts of these mixed garnets.

Thermoluminescent Properties of Cerium-Doped Lu2SO5 and Y2SiO5 Single Crystalline Films Scintillators Grown from PbO-B2O3 and Bi2O3 Fluxes

In this work we show the influence of material preparation technology on the thermoluminescent properties of single crystalline films (SCFs) of Ce3+-doped Lu2SiO5 (LSO) and Y2SiO5 (YSO) orthosilicates. LSO:Ce and YSO:Ce SCFs were grown by the liquid phase epitaxy method from two different melt-solutions based on PbO-B2O3 and Bi2O3 fluxes. Absorption, cathodoluminescence, and thermoluminescent properties of LSO:Ce and YSO:Ce SCFs grown from the two previously mentioned types of fluxes were compared, and results of spectrally resolved thermoluminescence measurements and thermoluminescent glow curves of SCFs recorded in different spectral ranges were presented. We have found that the observed differences in thermoluminescent properties of the SCFs under study can be caused by the domination of Ce4+ and Pb2+ emission centers in LSO:Ce and YSO:Ce SCFs grown using PbO-B2O3 flux, and Ce3+ and Bi3+ emission centers in the SCFs grown from Bi2O3 flux.

Luminescent and scintillation properties of Ce3+ doped Ca2RMgScSi3O12 (R = Y, Lu) single crystalline films

The work is dedicated to the growth and investigation of the luminescent and scintillation properties of single crystalline films (SCFs) of Ca2−xR1+xMg1+xSc1−xSi3O12:Ce (R = Y, Lu) mixed garnets with x = 0–0.25, grown using the liquid phase epitaxy method onto Y3Al5O12 substrates from PbO-B2O3 based flux. The absorption, luminescent and scintillation properties of Ca2−xY1+x Mg1+xSc1−xSi3O12:Ce and Ca2−xLu1+xMg1+xSc1−xSi3O12:Ce SCFs with x = 0 and 0.25 were investigated and compared with the reference YAG:Ce and LuAG:Ce SCFs. Using the Ca2+, Mg2+ and Si4+ alloying, the Ce3+ emission spectra in Ca2−xR1+xMg1+xSc1−xSi3O12:Ce (R = Y, Lu; x = 0–0.25) SCFs can be notably extended in the red range in comparison with YAG:Ce and LuAG:Ce SCFs due to the increase of crystal field strength and Ce3+ multicenter creation in the dodecahedral positions of the lattices of these mixed garnet compounds. Due to the formation of Ce4+ ions, the as-grown Ca2−x R1+xMg1+xSc1−xSi3O12:Ce (R = Y, Lu) SCFs at x = 0 and 0.25 show relatively low light yield. However, after annealing in reducing atmosphere (95% N2 + 5% H2) at T > 1000°C, a recharging Ce4+→Ce3+ takes place. After that, these SCFs possess the light yield about of 30% and 31% in comparison with the reference YAG:Ce and LuAG:Ce SCFs, respectively, and a fast scintillation response with the decay times in the ns range under α–particles excitation by 239Pu (5.15MeV) source.

Growth and luminescent properties of single crystalline films of Ce3+ doped Pr1−xLuxAlO3 and Gd1−xLuxAlO3 perovskites

The paper is dedicated to development of UV emitting scintillating screens for microimaging applications based on the single crystalline films (SCFs) of Ce doped Gd1−xLuxAlO3 and Pr1−xLuxAlO3 (x=0–1) multicomponent perovskites grown onto YAlO3 (YAP) substrates using the liquid phase epitaxy (LPE) method with the objective to improve the X-ray stopping power. Recently Riva et al. [1] have reported that the full set of GdxLu1−xAlO3 SCFs with x values in x=0−1.0 range can be crystallized on YAP substrates using this technique. We report here that PrxLu1−xAlO3 SCFs with x values in x=0–0.5 range can be grown also by the LPE method from PbO-B2O3 flux onto the same YAP substrates. The structural quality of the films was studied using X-ray diffraction. The optical properties of Ce3+ doped of Gd1−xLuxAlO3 and Pr1−xLuxAlO3 (x=0−1) multicomponent perovskite films, studied by traditional spectroscopic methods, such as absorption, cathodoluminescence, photoluminescence and light yield measurements under α–particles excitation, are also reported in this work. We have shown that Pb2+ flux related impurity has significantly larger influence on the light yield of Pr0.5Lu0.5AlO3:Ce, GdAlO3:Ce and Gd0.5Lu0.5AlO3:Ce SCFs in comparison with the YAP:Ce and LuAlO3:Ce counterparts grown onto YAP substrates.

Luminescent and scintillation properties of the Ce3+ doped Y3−xLuxAl5O12:Ce single crystalline films

The work is related to the investigation of scintillation and luminescent properties of single crystalline films (SCF) of solid solutions of Ce3+ doped Y3−xLuxAl5O12:Ce garnets with x value in the 0–3 range. We have shown a possibility of realization of high-energy shift of the Ce3+ ion emission spectrum in these garnets up to 22nm. We have also found that the light yield of the radioluminescence under α-particle excitation of LuAG:Ce SCF can exceed by 1.3 times the corresponding values for the YAG:Ce SCF counterpart. For investigation of the luminescent properties of Y3−xLuxAl5O12:Ce SCF at different x values the luminescent spectroscopy of these SCFs under excitation by synchrotron radiation in the VUV range was performed.

Single crystalline film scintillators based on Ce- and Pr-doped aluminium garnets

Luminescence and scintillation properties of single crystalline films (SCF) of Ce- and Pr-doped Y 3 Al 5 O 12 (YAG) and Lu 3 Al 5 O 12 (LuAG) garnets were analysed and compared with their bulk single crystal (SC) analogues. It was shown that the main peculiarities of luminescent properties of Ce- and Pr-doped YAG and LuAG SCF are due to the absence of Y Al and Lu Al antisite defects (AD) and to the extremely low concentration of vacancy-type defects in SCF with respect to SC. In SCF the absence of the AD-related traps results in faster energy transfer to the emission centres and accelerated scintillation response.