Synthesis and thermoluminescence characterizations of Sr2B5O9Cl:Dy3+ phosphor for TL dosimetry

Photoluminescence and Thermoluminescence in Dy3+ , Ce3+ and Tb3+ activated MgB4 O7 phosphor for dosimetry application

Samples of microcrystalline rare earth doped magnesium borate materials were synthesized via. modified solid state diffusion and were characterized by X-ray diffraction (XRD) and Scanning electron microscopy (SEM) techniques. Photoluminescence (PL) results of MgB₄ O₇ :Dy sample depicts blue emission resulted from (⁴ F_9/2 -⁶ H_15/2 ) transition peaked at 484 nm, which is much stronger than yellow emission arising due to the (⁴ F_9/2 -⁶ H_13/2 ) at 576 nm. From emission spectra of MgB₄ O₇ :Tb, it looks that, at higher concentration of Tb³⁺ ion, the green emission becomes strong and strong which directly relates the energy transfer from ⁵ D₃ excited state to ⁵ D₄ excited state by a cross-relaxation while blue emission gets suppressed in MgB₄ O₇ phosphors. The TL of the samples was taken immediately after the irradiation and compared the TL curve with CaSO₄ :Dy. MgB₄ O₇ :Dy showed very good TL sensitivity for the desirable dosimetric curve at about 218°C and the best glow curve structure. In comparison to dosimetric peak of MgB₄ O₇ :Ce and MgB₄ O₇ :Tb, MgB₄ O₇ :Dy phosphor is equally sensitive to CaSO₄ : Dy. MgB₄ O₇ :Dy and MgB₄ O₇ :Tb have shown linearity for 1-5 kGy dose. The activation energies and frequency factors are also calculated for samples MgB₄ O₇ :RE (RE=Dy, Tb, Ce) using peak shape method.

Luminescent Inorganic Mixed borate phosphors materials for lighting

The need of new materials with desirable optical properties has become important in recent year. In particular, a need has emerged for compounds having better luminescent properties in various practical applications. Introduction of rare earth ions as activators improves the luminescence properties of the compounds considerably. Boron is one of the most abundant elements in the nature. It readily combines with almost all other elements. In combination with oxygen; it forms borates comprising of various anions like BO₃ ^3- , B₂ O₅ ^4- , etc. Apart from these simple borates, several complex compositions exist involving mixed anions as well as double metal borates. Due to three-fold, or four-fold coordination of borate atoms Borates intrinsically possess characteristics that are advantageous for optical materials, which include wide transparency range, large electronic band gap, good thermal and chemical stability, low preparative temperature, optical stability with good nonlinear characteristics and exceptionally high optical damage threshold. The unique crystal structure of borates determines their enhanced UV transparency, good nonlinearity and relatively high resistance against laser induced damage. Some of these complex borates showing interesting luminescence properties are covered in this review. These include double borates containing rare earths RM₃ (BO₃ )₄ , Pentaborates LaMgB₅ O₁₀ , M₃ R₂ (BO₃ )₄ , where M is alkaline earth, mixed anion borates like aluminoborate SrAl₂ B₂ O₇ , Silicate-Borates like pekovite, SrB₂ Si₂ O₈ , Haloborates, M₂ B₅ O₉ X, where M is alkaline earth and X is halogen, phosphate borates, MBPO₅ , where M is alkaline earth. Phosphors base on these compositions find use in various applications like fluorescent lamps, colour TV, plasma display panels, high intensity discharge lamps based on Xenon, optically pumped solid state lasers, eye safe lasers, X-ray imaging.

Ca2 Al2 SiO7 :Ce3+ phosphors for mechanoluminescence dosimetry

A series of Ce³⁺ ion single-doped Ca₂ Al₂ SiO₇ phosphors was synthesized by a combustion-assisted method at an initiating temperature of 600 °C. The samples were annealed at 1100 °C for 3 h and their X-ray diffraction patterns confirmed a tetragonal structure. The phase structure, particle size, surface morphology and elemental analysis were analyzed using X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy techniques. Thermoluminescence (TL) intensity increased with increase in ultraviolet (UV) light exposure time up to 15 min. With further increase in the UV irradiation time the TL intensity decreases. The increase in TL intensity indicates that trap concentration increased with UV exposure time. A broad peak at 121 °C suggested the existence of a trapping level. The peak of mechanoluminescence (ML) intensity versus time curve increased linearly with increasing impact velocity of the moving piston. Mechanoluminescence intensity increased with increase in UV irradiation time up to 15 min. Under UV-irradiation excitation, the TL and ML emission spectra of Ca₂ Al₂ SiO₇ :Ce³⁺ phosphor showed the characteristic emission of Ce³⁺ peaking at 400 nm (UV-violet) and originating from the Ce³⁺ transitions of 5d-4f (² F_5/2 and ² F_7/2 ). The photoluminescence (PL) emission spectra for Ca₂ Al₂ SiO₇ :Ce³⁺ were similar to the ML/TL emission spectra. The mechanism of ML excitation and the suitability of the Ca₂ Al₂ SiO₇ :Ce³⁺ phosphor for radiation dosimetry are discussed. Copyright © 2016 John Wiley & Sons, Ltd.

Photoluminescence and thermoluminescence properties of Li₂O-Na₂O-B₂O₃ glass

Influence of Nd(3+) concentration on the optical and thermoluminescence (TL) properties of melt-annealed synthesized 10 Na2O: 20 Li2O: (70-x) B2O3 : xNd2O3, where 0.1≤ x ≤0.7 (LNB) glasses are determined. The absence of sharp peaks in X-ray diffraction patterns confirms the amorphous nature of the prepared glasses. The photoluminescence spectra under 800 nm laser excitations at room temperature exhibit three prominent peaks centred at 538, 603 and 675 nm corresponding to the transitions of (4)G(7/2) → (4)I(9/2), [(4)G(7/2) → (4)I(11/2), (4)G(5/2) → (4)I(9/2)] and [(4)G(7/2) → (4)I(13/2), (4)G(5/2) → (4)I(11/2)], respectively. The TL glow curve exhibits a prominent peak (T(m)) at 180°C. The best performance of the prepared glass was found at 0.5 mol% of Nd2O3. We achieved a good linearity of TL response against dose between 0.5 to 4.0 Gy. The calculated value of the effective atomic number, Z(eff), is 7.55 which is nearly tissue equivalent (Z(eff) = 7.42). These promising features demonstrate the capability of the aforementioned glass to be used as a radiation dosimeter.

HIGHLIGHTS

The thermoluminescence and optical properties of new compositions of lithium sodium borate glasses doped with Nd(3+) ions were reported. Attractive features were obtained from the TL, PL and UV-Vis light analysis. Three upconversion luminescences permitting green, orange and red emissions were observed.