Physical, optical and luminescence properties of B₂O₃-SiO₂-Y₂O₃-CaO glasses with Sm³⁺ions for visible laser applications

Karki, Sujita,Kesavulu, C.R.,Kim, H.J.,Kaewkhao, J.,Chanthima, N.,Ruangtaweep, Y. Elsevier 2018 Journal of luminescence Vol.197 No.-

<P><B>Abstract</B></P> <P>Silicoborate glasses with composition of (BSYCaSm:(55-x)B<SUB>2</SUB>O<SUB>3</SUB>+ 10SiO<SUB>2</SUB> +25Y<SUB>2</SUB>O<SUB>3</SUB> +10CaO + xSm<SUB>2</SUB>O<SUB>3</SUB>), (where, x= 0.05, 0.10, 0.20, 0.25, 0.30, 0.40, 0.50, mol%) have been synthesized by using the well-known melt quenching technique. The present work deals with physical, optical, photoluminescence, X-ray luminescence and decay time studies of silicoborate glasses. Judd-Ofelt (JO) intensity parameters (Ω<SUB>2,</SUB> Ω<SUB>4</SUB> and Ω<SUB>6</SUB>) and radiative properties for the important luminescent level of Sm<SUP>3+</SUP> ions were derived by using the absorption spectrum of 0.3mol% Sm<SUB>2</SUB>O<SUB>3</SUB> doped glass. The luminescence spectra in the visible region was obtained due to <SUP>4</SUP>G<SUB>5/2</SUB> → <SUP>6</SUP>H<SUB>J</SUB> (5/2, 7/2, 9/2 and 11/2) transition of Sm<SUP>3+</SUP> ion under 401nm excitation. The decay profile for the <SUP>4</SUP>G<SUB>5/2</SUB> level of Sm<SUP>3+</SUP> ions was analyzed and found that for lower concentration (≤ 0.20mol%) it is single exponential in nature whereas for higher concentration (≥ 0.25mol%), it turns in to non-exponential due to the transfer of energy between donor (excited state Sm<SUP>3+</SUP>ion) and acceptor (ground state Sm<SUP>3+</SUP> ion). As the concentration of Sm<SUP>3+</SUP> ions increases the decay time of <SUP>4</SUP>G<SUB>5/2</SUB> state decreases. The well-known Inokuti-Hirayama (IH) model was used for fitting the non-exponential decay curves where S = 6 indicates that energy transfer process is of dipole-dipole type. Hence, in the present work, intense transition of <SUP>4</SUP>G<SUB>5/2</SUB> → <SUP>6</SUP>H<SUB>7/2</SUB> (601nm) is found to be suitable for reddish-orange laser emission. CIE chromaticity diagram has been performed for verifying the results of fluorescence in visible laser applications at 601nm.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Synthesis, Luminescence and Optical Properties of a CaMoO4 Nano-Powder Prepared by Using the Precipitation Method

Sujita Karki,Pabitra Aryal,하대훈,김홍주,박향규,Indra Raj Pandey 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.7

Nano powders of CaMoO$_4$ were synthesized by using the precipitation method, and the obtained powders were dried inside a vacuum oven at 120 $^\circ$C. The phases of powders were analyzed by using X-ray diffraction (XRD), which revealed that CaMoO$_4$ was free from any extra phases. The surface morphologies of the powders were studied by using transmission electron microscopy (TEM), and the average particle sizes were quite small, being in the range of 7 nm. The optical properties were characterized by using ultraviolet-visible (UV-vis) absorption spectroscopy and the optical energy band gap was found to be 5.51 eV. The fluorescence decay time and the luminescence spectrum of the sample were measured under the excitation by Laser (266 nm), X-ray and proton sources. The obtained results were compared with the CaMoO$_4$ bulk crystal and sintered powder obtained from the solid state reaction.

Crystal growth, optical and luminescence properties of Na₆Mo₁₁O₃₆ single crystal

Pandey, Indra Raj,Karki, Sujita,Kim, H.J.,Lee, M.H.,Kim, Y.D. Elsevier 2019 Journal of crystal growth Vol.512 No.-

<P><B>Abstract</B></P> <P>The inorganic material Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> was synthesized by solid-state reaction, and a single crystal of the compound was grown using the Czochralski technique. The crystal structure of the compound was confirmed by X-ray diffraction (XRD) analysis. The luminescence light yield and fluorescence decay time of the crystal were studied in a temperature range from room temperature to 10 K using a 280 nm light emitting diode (LED) source. The Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> crystal has no luminescence at room temperature, however, the luminescence intensity is enhanced at low temperatures. Transmittance spectrum measurement was performed to study the optical quality of the crystal. The luminescence light yield of the Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> was compared with that of a Li<SUB>2</SUB>MoO<SUB>4</SUB> crystal at different low temperatures. Because of the possibility of growing a single crystal of Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB>, which has a significant luminescence light yield at 10 K and no heavy elements, this crystal can be a good candidate for a rare event search experiment searching for neutrinoless double beta (0νββ) decay at cryogenic temperatures.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Single crystals of Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> is grown for first time. </LI> <LI> Powder XRD result of Na<SUB>2</SUB>Mo<SUB>4</SUB>O<SUB>13</SUB> and Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> compound shows that, both compound has almost the same phase. </LI> <LI> Luminescence properties of new Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> crystal is reported. </LI> <LI> The luminescence result of Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> at 10 K is compared with Li<SUB>2</SUB>MoO<SUB>4</SUB> crystal. </LI> <LI> At 10 K, luminescence light yield of Na<SUB>6</SUB>Mo<SUB>11</SUB>O<SUB>36</SUB> is almost double than Li<SUB>2</SUB>MoO<SUB>4</SUB> crystal. </LI> </UL> </P>

Optical Properties in the Visible Luminescence of SiO2:B2O3:CaO:GdF3 Glass Scintillators Containing CeF3

J. M. PARK,김홍주,Sujita Karki,J. Kaewkhao,B. Damdee,S. Kothandaraman,S. Kaewjaeng 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.11

CeF3-doped silicaborate-calcium-gadolinium glass scintillators, with the formula 10SiO2:(55- x)B2O3:10CaO:25GdF3:xCeF3, were fabricated by the melt-quenching technique. The doping concentration of the CeF3 was from 0.00 mol% to 0.20 mol%. The optical properties of the CeF3 doped glass scintillators were studied by using various radiation sources. The transition state of the CeF3- doped glass scintillators studied by using the absorption and photo-luminescence spectrum results. The X-ray, photo, proton and laser-induced luminescence spectra were also studied to understand the luminescence mechanism under various conditions. To understand the temperature dependence, the laser-induced luminescence and the decay component of the CeF3-doped glass scintillator were studied while the temperature was varied from 300 K to 10 K. The emission wavelength spectrum showed from 350 nm to 55 nm under various radiation sources. Also the CeF3-doped glass scintillator have one decay component as 34 ns at room temperature.

Optical properties in the visible luminescence of SiO2:B2O3:CaO:GdF3 glass scintillators containing CeF3

Park, J. M.,Kim, H. J.,Karki, Sujita,Kaewkhao, J.,Damdee, B.,Kothan, S.,Kaewjaeng, S. 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol. No.

<P>CeF3-doped silicaborate-calcium-gadolinium glass scintillators, with the formula 10SiO(2):(55-x)B2O3:10CaO:25GdF(3):xCeF(3), were fabricated by the melt-quenching technique. The doping concentration of the CeF3 was from 0.00 mol% to 0.20 mol%. The optical properties of the CeF3 doped glass scintillators were studied by using various radiation sources. The transition state of the CeF3-doped glass scintillators studied by using the absorption and photo-luminescence spectrum results. The X-ray, photo, proton and laser-induced luminescence spectra were also studied to understand the luminescence mechanism under various conditions. To understand the temperature dependence, the laser-induced luminescence and the decay component of the CeF3-doped glass scintillator were studied while the temperature was varied from 300 K to 10 K. The emission wavelength spectrum showed from 350 nm to 55 nm under various radiation sources. Also the CeF3-doped glass scintillator have one decay component as 34 ns at room temperature.</P>

Enhanced visible emissions of Pr³⁺-doped oxyfluoride transparent glass-ceramics containing SrF₂ nanocrystals

Kesavulu, C.R.,Viswanath, C.S. Dwaraka,Karki, Sujita,Aryal, Pabitra,Kim, H.J.,Jayasankar, C.K. Elsevier 2018 CERAMICS INTERNATIONAL Vol.44 No.2

<P><B>Abstract</B></P> <P>The Pr<SUP>3+</SUP>-doped oxyfluoride transparent glass and glass-ceramic (GC) with the composition of 41SiO<SUB>2</SUB> + 10Al<SUB>2</SUB>O<SUB>3</SUB> + 25.5LiF + 23SrF<SUB>2</SUB> + 0.5Pr<SUB>2</SUB>O<SUB>3</SUB> were prepared and investigated their optical and luminescence properties. The formation of SrF<SUB>2</SUB> nanocrystals in GC has been confirmed by X-ray diffraction (XRD) and transmission electron micrographs (TEM). The Fourier transform infrared spectroscopy (FT-IR) studies were used to examine the network structure characteristics of silicates in the glass matrices. The XRD and TEM results suggest that the Pr<SUP>3+</SUP> ions are progressively incorporated into the SrF<SUB>2</SUB> nanocrystals in the GC with increase in time of thermal treatment at 650°C, corresponding to the first crystallization temperature of the glass. The obtained visible emissions of Pr<SUP>3+</SUP>-doped GC are several times enhanced than that in the glass and the lifetime of the <SUP>3</SUP>P<SUB>0</SUB> level of the Pr<SUP>3+</SUP> ions in glass and GC are found to be 7 and 12μs, respectively. Therefore, the enhanced visible emission and lifetimes in GC are due to the incorporation of Pr<SUP>3+</SUP> ions into the lower phonon energy of SrF<SUB>2</SUB> nanocrystals in the GCs. Moreover, the smaller difference in ionic radius between the added trivalent ions (Pr<SUP>3+</SUP>) and Sr<SUP>2+</SUP> induces the larger enhancement of luminescence intensity in the GC. Hence, these enhanced visible luminescence properties indicate that the present glass and GC could be useful for photonic device applications.</P>