Investigations of Thermal Stability and Spectroscopic Features of Sm3+ Doped Strontium Aluminate Glasses

In the present work, a series of Sm3+ doped transparent strontium aluminate glasses with the composition Al2O3-(3-x)SrO: xSm3+ (x = 0, 0.01, 0.03, 0.06, 0.1, 0.2) were fabricated by a containerless process using an aerodynamic levitation furnace. The structural characteristics, density, Vicker’s hardness, and thermal and spectroscopic behaviors of these glasses were investigated. All the glasses exhibit excellent thermal stabilities (Tg ≥ 792 °C) and the glass-forming ability is enhanced with the increasing content of Sm3+. The emission spectra recorded under an excitation of 404 nm show four emission transitions as a result of 4G5/2 translated to the lower states of 6H5/2, 6H7/2, 6H9/2, and 6H11/2, and a bright orange-reddish luminescence can be observed in Al2O3-(3-x)SrO: xSm3+ glasses. The high thermal stability, good glass-forming ability and excellent hardness provide new options for the development of visible orange-reddish lasers and smart photoluminescent glass coating materials.

Effect of the Concentration of SrAl2O4: Eu2+and Dy3+ (SAO) on Characteristics and Properties of Environment-Friendly Long-Persistent Luminescence Composites from Polylactic Acid and SAO

We report luminous polylactic acid (PLA) composite prepared via a solvent casting method using different amounts of phosphor strontium aluminate (SrAl2O4: Eu2+ and Dy3+) (SAO). The reason for doing this is that the changes of fluorescence and mechanical properties in the composites with different SAO contents can be directly evaluated. The SAO particles should have a variety of excellent characteristics in the PLA matrix, among which dispersibility and compatibility are particularly important; so, they can be modified by 3-aminopropyltriethoxysilane (APS) to achieve the target characteristics. The results showed that the fluorescence and mechanical properties were affected by SAO addition. The mechanical properties significantly improved with 5 wt% SAO; further, addition had no impact. And the emission band of fluorescence and phosphorescence is just at the peak of 524 nm. The composites with 15 wt% SAO have the best fluorescence properties. The fluorescence decreased with further doping. Fluorescence decay curves with various amounts of SAO particles show a similar tendency as pure SAO particles; the speed of decrease in afterglow intensity was higher for the first 30 min. In addition, the detailed morphological scanning and study by scanning electron microscope (SEM) showed that the particles had good adhesion to the matrix. In conclusion, the concentration of SAO into the PLA matrix impacts the fluorescence and mechanical properties of a SAO/PLA composite material.

Photocatalytic Reaction Properties of TiO2-Supported on the Long Lasting Phosphor: Sr4Al14O25:Eu2+,Dy3+

The TiO2/Sr4Al14O25:Eu2+,Dy3+ photocatalytic composite was prepared by depositing the nano-crystalline titanium dioxide layer on the long-lasting phosphor substrate of strontium aluminate, using a low-pressure chemical vapor deposition (LP-CVD). The photocatalysis characteristic was studied by examining the photodegradation of benzene (C6H6) gas under UV, visible light illumination, and in the darkness. The photocatalytic composite of TiO2-deposited Sr4Al14O25:Eu2+,Dy3+ showed an active photocatalytic reactivity under UV-light as well as visible-light illumination. The mechanism of the photocatalysis reaction for the TiO2-deposited strontium aluminate phosphor composite was interpreted in point of the energy band structure and phosphorescent emission. The coupling of nanocrystalline TiO2 with the strontium aluminate phosphor might result in an energy band bending at the interface of TiO2/Sr4Al14O25:Eu2+,Dy3+, making the titanium dioxide at the junction to be photo-reactive even in a visible wavelength region. In addition, the depth profile of Auger electron spectroscopy (AES) confirmed a possible formation of oxygen vacancies at the interface between TiO2 and Sr4Al14O25:Eu2+,Dy3+. Then, oxygen defects create extra electrons which may excited subsequently to the conduction band and participate in a photocatalytic reaction, resulting in an enhancement of the photodecomposition of benzene. The LP-CVD TiO2-strontium aluminate phosphor was also photoactive in the darkness because of light emission from the long lasting phosphor. Also, the TiO2-deposited Sr4Al14O25:Eu2+,Dy3+ long lasting phosphor was analyzed by a XRD (X-ray diffraction), TEM (transmission electron microscopy), UV/visible spectroscopy and AES.

Strontium Aluminate-Based Long Afterglow PP Composites: Phosphorescence, Thermal, and Mechanical Characteristics

A tremendous potential has been observed in the designing of long afterglow materials for sensing, bioimaging, and encryption applications. In this study, two different strontium aluminate-based luminescent materials; SrAl2O4: Eu, Dy (S1), and Sr4Al14O25: Eu, Dy (S2) were melt-mixed with polypropylene (PP) matrix, and the phosphorescence properties were evaluated. After excitation at 320 nm, the PP/S1 composite exhibited a green emission and the PP/S2 generated a blue emission at 520 nm and 495 nm, respectively. The emission spectra intensity increased by increasing the content of these luminescent fillers. The attenuated total reflection-Fourier transform infrared (ATR-FTIR) experiments show that no chemical reaction occurred during the melt-mixing process. The differential scanning calorimetry (DSC) results revealed that the total crystallinity of the composites reduced by increasing the amount of the fillers; however, no changes in the temperature of melting (Tm) and crystallization (Tc) of PP were observed. Both fillers improved the impact strength of the composites, but the tensile strength (TS) and modulus (TM) decreased. Poly (ethylene glycol) dimethyl ether (P) plasticizer was used to improve the filler-matrix interaction and its dispersion; nevertheless, it adversely affected the intensity of the luminescence emissions.