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In this paper, we investigate and report the effects of Si4+/Al3+ (SiO 2 /Al 2 O 3) molar concentration ratio on the self-reduction process of Yb3+ to Yb2+ ions and upconversion (UC)-, visible (VIS)- emission spectra, direct optical bandgaps (DOB), indirect optical bandgaps (IOB) of Bin+/Ybm+, Er3+/Bin+, and Er3+/Bin+/Ybm+ (n, m = 3, 2) co-doped SiO 2 –Al 2 O 3 –MgO–TiO 2 (SAMT) magnesium aluminum silicate glasses. The valence states of the bismuth (Bi), and Ytterbium (Yb) elements in the raw materials mixture existing in the SAMT glass were determined using X-ray photoelectron spectroscopy (XPS) spectra analysis. With the increase of Al3+ molar concentration from 16 mol. % up to 20, 24, 28 and 32 mol. % corresponding to the Si4+/Al3+ (SiO 2 /Al 2 O 3) molar concentration ratio of 3.4, 2.5, 1.9, 1.5, and 1.2, the self-reduction process of Yb3+ to Yb2+ ions was enhanced and thus significantly affected the DOB, IOB, the intensities of UC-, VIS- emission spectra of Bin+/Ybm+, Bin+/Er3+, and Bin+/Er3+/Ybm+ (n = 2, 3) co-doped SAMT glasses under excitation of 473 nm, 808 laser diode (LD) and 980 nm LD. In addition, the CIE 1931(x, y) color coordinates for VIS- and UC- emissions spectra of Bin+/Ybm+, Bin+/Er3+ (n = 2, 3) co-doped SAMT under excitation of 473 nm and 808 nm LD are also calculated and determined in the CIE 1931(x, y) chromaticity diagram. • Effect of Si4+/Al3+ ratio on the self-reduction process of Yb3+ to Yb2+ ions were investigated. • XPS results determined existence of Bi3+, Bi2+, Yb3+, and Yb2+ ions in SiO 2 –Al 2 O 3 –MgO–TiO 2 glass. • CIE1931 for VIS, UC emissions of Bin+/Er3+/Ybm + under excitation of 473, 808 nm were determined. [ABSTRACT FROM AUTHOR]

Silicate-Titania (SiTi) glass-ceramics doped with Pr3+ (0.6, 1.6, 2.4 and 3.6 mol%) ions were prepared by sol-gel technique. The materials were characterized by powder XRD, FTIR, TEM, EDX, Optical absorption and Photoluminescence spectroscopy. The identification of non-bridging oxygen (NBO) formation and the removal of OH groups are validated through analysis of the FTIR spectra. Additionally, measurements using XRD and TEM showed that the samples contain nano-sized crystallites. The three phenomenological Judd–Ofelt (J–O) intensity parameters Ω 2 , Ω 4 , and Ω 6 were obtained and used to analyze different radiative characteristics for the fluorescence levels of Pr3+ in the glass ceramic, including radiative lifetime, branching ratio, radiative transition probability and stimulated emission cross-section. Several emissions were observed in the visible region, among which the 1D 2 →3H 4 in the orange-red region is the most intense. All of these reported branching ratios, stimulated emission cross-sections, and visible emission spectra point to the possibility of employing them as red region lasers. The CIE chromaticity coordinates from all of the emission spectra were also assessed to determine if these materials are suitable for orange-red phosphors. According to CIE chromaticity investigations, 1.6 mol% of Pr3+ ion concentration is ideal for SiTiPr glass-ceramic for use as red phosphors and possibly red lasers. • SiO 2 –TiO 2 glass ceramics doped with Pr3+ are synthesized by sol-gel technique. • TiO 2 nanocrystals of size around 10–20 nm are formed. • Judd-Ofelt parameters and radiative parameters are calculated. • Strong emissions in the orange-red region are observed under blue excitation. • Cross-relaxation reduces luminescence at high Pr3+ concentration. [ABSTRACT FROM AUTHOR]

Hydrothermal and thermolysis techniques were used to create ZnWO 4 and 0.9ZnWO 4 -0.1MS (M = Cd, Zn, Pb) samples. The formed phases in each sample and their structure and microstructure were examined using Raman spectroscopy, Fourier-transform infrared spectroscopy and Rietveld refinement of Synchrotron x-ray diffraction data. The composition and morphology of the formed samples were investigated via scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDS). The average crystallite size remains relatively constant regardless of the different metal chalcogenides. MS/ZnWO 4 samples have two distinct morphologies. The UV diffuse reflectance spectroscopy (UV-DRS) technique is used to investigate the linear and nonlinear optical parameters for different samples. Alloying ZnWO 4 with CdS or PbS affects the photo response region of the sample to include visible light. MS/ZnWO 4 (MS=CdS, ZnS, PbS) samples have optical band gap values of 2.56, 2.43, 2.99 and 3.1 eV, respectively. The CdS/ZnWO 4 and ZnS/ZnWO 4 samples exhibit the highest refractive index and optical dielectric constant values within the visible range. CdS or PbS/ZnWO 4 samples show the highest nonlinear optical parameters values within the visible range. The impact of MS samples on the photoluminescence emission of ZnWO 4 was explored. The CIE chromaticity diagram reveals that MS/ZnWO 4 (M = Zn and Pb) samples display a different degree of blue color while CdS/ZnWO 4 sample reveals green-yellow colors. • Raman spectra analysis confirmed the formation of CdS phase, nonexistence of the ZnS phase and could not detect PbS phase. • The values of n and k are influenced by the measured range of wavelengths and the type of alloying sample (MS) with ZnWO 4. • All samples exhibit a wide-ranging emission in the blue-green region. • The examined samples become more sensitive to daylight. [ABSTRACT FROM AUTHOR]

Substituted hydrazides have significant potential as nonlinear optical materials. In this contribution, synthesis and structural (X-ray crystallography, UV, IR, and Raman spectroscopy) characterization of a novel NLO material, E- N '-(4-formylbenzylidene)furan-2-carbohydrazide (4FBC), is presented. The Hirshfeld surface analysis allowed for the investigation of the intermolecular interactions within the crystal structure and the most significant contacts with the neighboring units were examined. The structural characterization is amended by quantum-chemical optimization employing several common functionals, and a comparison between crystallographic and predicted parameters determined the appropriate level of theory. The CAM-B3LYP/6–311++G(d,p) level of theory was used for further calculations, as the lowest differences in bond lengths and angles were obtained for the structure optimized at this level of theory. The vibrational and UV-VIS spectra were assigned, and the effects of different groups were discussed. The experimental electronic transition energy was well reproduced upon optimizing the excited state. The Quantum Theory of Atoms in Molecules (QTAIM) and Natural Bond Orbital (NBO) theory were used to quantify intramolecular stabilization interactions. The NLO properties of 4FBC were proven through the Z-scan experimental determination of the absorption coefficient and nonlinear refractive index. [Display omitted] • E- N '-(4-formylbenzylidene)furan-2-carbohydrazide hydrate crystal has been prepared. • Structure and spectra analyses were done at CAM-B3LYP/6–311++G(d,p) level of theory. • Different intermolecular interactions within crystal structure were examined. • Intramolecular interactions were investigated using NBO and QTAIM analyses. • Z-scan analysis proved the possible use as a non-linear optical material. [ABSTRACT FROM AUTHOR]

Cr-doped monoclinic β-Ga 2 O 3 –7%In 2 O 3 single crystals were grown by the floating zone technique with radiation heating. The dark green color of the as-grown crystals transforms to light green upon crystals annealing in an oxygen atmosphere. Excitation spectra reveal characteristic Cr3+ bands in the visible spectral region and complex features in the UV region. Comparisons between as-grown and annealed crystals show variations in chromium excitation bands. UV or visible light irradiation induces intense Cr3+ luminescence in the red spectrum. The R 2 line diminishes at low temperatures, and the R 1 line dominates, exhibiting a blue shift compared to gallium oxide. Raman spectroscopy identifies phonon frequencies, revealing distinct modes associated with crystal lattice vibrations. The fine structure in the luminescence spectrum is attributed to vibronic transitions involving R lines and specific phonon modes. The R 1 line in β-Ga 2 O 3 –7%In 2 O 3 single crystals has a larger FWHM than in β-Ga 2 O 3. Decomposition of R 1 -line reveals inhomogeneous broadening, with Gaussian fits indicating several types of Cr3+ centers, attributed to the octahedrally-coordinated Ga- and In positions, as well as is sensitive to oxygen non-stoichiometry. Photoluminescence decay kinetics measured at 695 nm (R 1 (Ga)-line) have a single-exponential decay at lower temperatures with a lifetime of 2.8 ms at 4.5 K. Temperature dependence of lifetime for the studied crystals is consistent with the previously studied β-Ga 2 O 3 :Cr and confirms an application potential of the material for low-temperature non-contact luminescence thermometry and light sources in deep red or near-IR spectral region. • Cr-doped β-Ga 2 O 3 –7%In 2 O 3 crystals grown by the floating zone technique have been characterized. • The temperature dependences of the photoluminescence spectra of Cr3+ ions were studied. • R 2 line diminishes at low temps and R 1 line dominates, exhibiting blue shift compared to pure β-Ga 2 O 3. • Luminescence spectrum analysis reveals several types of Cr3+ centres. • Photoluminescence decay study at 695 nm suggests potential for low-temperature thermometry. [ABSTRACT FROM AUTHOR]

In this paper, Sr 2 SiO 4 phosphors with different Sm3+ concentrations and Sr 2 SiO 4 :0.006Sm3+ phosphors obtained from the coal gasification slag as raw materials have been synthesized by the high-temperature solid-phase method. The influence of Sm3+ ions and the purity of SiO 2 on the structural and optical attributes of Sr 2 SiO 4 have been investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible (UV–Vis) spectrum, photoluminescence (PL) spectra and fluorescence lifetime analysis. XRD results showed that the doping ions have entered into the host lattice, and SEM shown the crystallite sizes have been found to vary from 1 to 3 μm. PL spectra displayed that the emission intensity of the samples increased with the increase in concentrations of Sm3+ ions. At the optimum doping concentration, the luminous intensity and fluorescence lifetime of the sample prepared by the purified silica is much higher than that of the phosphor prepared by the chemical product silica, which is close to that of the pure chemical reagent. Finally, we explored the application of fluorescent powder in pc-WLED devices. Notably, the devices exhibited excellent luminous performance at 20 mA current. The results demonstrate that coal gasification slag (CGS) product can be used to synthesize brilliant materials with potential uses for the pc-WLED technology. • The high fluorescence intensity Sm3+ doped Sr 2 SiO 4 phosphors were prepared using silica extracted from coal gasification slag as raw materials. • Effect of raw material purity was investigated from the excitation and emission spectra analysis. • The luminescence performance of Sr 2 SiO 4 phosphor is found to be strongly dependent on rare earth ions. [ABSTRACT FROM AUTHOR]

We conducted a study to analyze the structural, morphological, and optical properties of Mg 0.6 Cu 0.4 FeCrO 4 spinel ferrite samples synthesized by the sol-gel method and sintered at two different temperatures, 900 °C and 1100 °C. The infrared spectrum analysis revealed the presence of only the tetrahedral stretch band (ν A), which had frequencies of 585 cm−1 for 900 °C and 586 cm−1 for 1100 °C. The bandgap energy and Urbach energy values decrease with increasing sintering temperature. The bandgap energy decreases from 1.20 eV to 1.06 eV, while the Urbach energy values decrease from 1.26 eV to 1.11 eV. Emphasis has been placed on the analysis of key aspects such as refractive index(n), optical conductivity (σ opt), extinction coefficient (k), penetration depth (ẟ), dielectric tangent loss, Q-factor, and dielectric constant. Optical studies have provided confirmation that Mg 0.6 Cu 0.4 FeCrO 4 spinel ferrites exhibit properties suitable for optoelectronics applications. • -The impact of sintering temperature on structural and morphological properties. • The effect of sintering temperature on optical properties. [ABSTRACT FROM AUTHOR]