Optical energy bandgap tuning of spinel zinc stannate by erbium/ytterbium doping

This work shows the results of an optical energy bandgap (Eg) investigation supported by scanning electron microscopy (SEM) of spinel-type zinc stannate (Zn2SnO4) upon doping with rear earth (RE3+) ions (Er3+, Yb3+). The powder samples are synthesized by a mechanochemical solid-state method with the final annealing step at 1200 C. The reference Zn2SnO4 powder sample bandgap (3.87 eV) turning lower upon doping, precisely to 3.5 eV, and 3.37 eV bandgap values found for Er-doped Zn2SnO4 and Er,Yb-codoped Zn2SnO4 powder samples, respectively is a confirmation of the successful incorporation of the RE3+ ions into the Zn2SnO4 host structure. Morphology of the obtained powders shows, in general, the non-uniformly shaped agglomerates, while their particle sizes follow up the bandgap decreasing trend with doping

Microstructure and thermal characterization of Mo-doped Li6.87Nb2.34Ti5.78O21 solid-solution ceramics

In this work, the microstructure and thermal properties of lithium-niobium-titanium-oxide (Li-Nb-Ti-O) solid-solution ceramics were investigated using the X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) techniques. XRD and SEM analysis confirmed that Li-Nb-Ti-O ceramic sample synthesized by solid-state method reaches the desired composition of so-called Mphase of the Li2O-Nb2O5-TiO2 ternary system (Li6.87Nb2.34Ti5.78O21) that should have excellent microwave dielectric properties. The M-phase was obtained with lower than 1000ºC sintering temperature by doping with MoO3 as flux material, which makes this kind of ceramic material suitable for the low temperature co-fired ceramic (LTCC) technology applications. The heat flow data obtained from DSC measurement were used to calculate the specific heat capacity (Cp) of synthesized Li6.87Nb2.34Ti5.78O21 solid-solution ceramics, which is the property of a material that tells about its stability and functionality

Combined experimental and DFT study of lithium-indium-oxide structure and vibrational properties

A promising lithium-indium-oxide (LiInO2) wide band-gap semiconductor for scintillating detection, photoluminescence, and photocatalysis [1-3] was prepared by a mechanochemical solid-state synthetic procedure that can be found elsewhere [3]. Its structure and morphology were investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. SEM images show agglomerates of relatively uniform size of around 300 nm spherical-shaped particles of LiInO2 powder, while the XRD pattern confirmed the formation of the nanocrystalline tetragonal structure withamdI /41 space group (no. 141) symmetry. Detailed vibration analysis, together with the assignments of the band modes, was performed through the best-fit match of the experimental and density functional theory (DFT) calculated Raman spectrum. Geometry optimizations and vibrational frequencies calculations were conducted using B97-1 functional correlation [4] and LanL2DZ was used as a basis set

Vaaisible upconversion emission of Er3+-doped and Er3+/Yb3+-codoped LiInO2

Lithium-indium oxide is a high-density (5.9 g center dot cm(-3)), wide band-gap semiconductor with promising applications for scintillating detection of solar neutrinos as well as for efficient phosphorescence when doped with Er3+ or Sm3+ ions. In this report, we demonstrate visible upconversion emission of Er3+-doped LiInO2 synthesized by a simple solid-state chemistry procedure and discuss mechanisms responsible for pumping the Er3+ ions to upper levels. Intense upconversion emission is observed in the green and red spectral regions under near-infrared excitation, and it is greatly enhanced by co-doping with Yb3+ ions. We also examined the upconversion intensity change as a function of temperature, and, consequently, possible applications of this material as a low-temperature sensor

Pore microstructure characterization of Zn2SnO4 using mercury intrusion porosimetry

The zinc stannate (Zn2SnO4) is marked as a promising semiconductor material to be used in a field of environmental protection and photocatalysis especially when its band gap is adjusted to enough narrow value to provide its applicability under the visible light irradiation. A traditional solid-state procedure was used to synthesize Zn2SnO4 when a stoichiometrical mixture of starting zinc oxide (ZnO) and tin oxide (SnO2) powders where mechanochemically activated by grinding in a planetary ball mill for 160 min and additionally annealed at 1200°C for 2 h. In this paper, we investigate the most important textural features of the Zn2SnO4 powder for its usage in the photocatalytic degradation of the organic pollutants from wastewaters. Mercury intrusion porosimetry was combined with the scanning electron microscopy to study morphology and surface properties, like specific pore volume, specific surface area, apparent density, and total porosity

Synthesis and characterization of (Y,Me)NbO4:Er,Yb phosphors: Influence of local lattice disorders

Yttrium niobate (YNbO4) is considered to be a self-activated phosphor with a strong emission band in the blue region originating from the NbO4 3- group, but also an effective host for various luminescent-based doping-altered applications with different rare-earth ions [1-4]. Here, (Y0.8-z,Mez)NbO4:Er,Yb (z = 0, 0.1, 0.2) phosphors with 0.05 erbium and 0.15 ytterbium as up-conversion (UC) activator and sensitizer, respectively, and different metal ions (Me) replacements of Y3+ ions that launch the host local lattice disorders, were synthesized by the traditional solid-state reaction method. The starting metal oxide precursors in the appropriate molar ratio were mixed in a ball mill at 100 rpm for 8 hours, then preannealed at 800 °C for 4 hours, and finally annealed at 1200 °C for 4 hours. The morphology of the synthesized phosphors and their particle size and shape were examined by scanning electron microscopy. X-ray diffraction measurements were used to confirm the crystal structure of samples. The emission spectra of Y0.8Er0.05Yb0.15NbO4 at room temperature under the excitation of 980 nm show green and red visible UC and near-infrared emission bands of very low intensity, which originate from energy transfer UC processes between Yb3+ and Er3+ ions and which are attributed to (2H11/2, 4S3/2) → 4I15/2, 4F9/2 → 4I15/2, and 4I9/2 → 4I15/2 transitions of Er3+ ions, respectively. The lifetime of the 4S3/2 excited energy level of Er3+ in Y0.8Er0.05Yb0.15NbO4 that depends on the host and plays an essential role in infrared to visible UC is 0.198 ms. UC mechanisms, the intensity of the UC emission, and changes in lifetime caused by different Me-ions entering the host lattice were discussed.ICOM&IWPPP 2022 : August 29 - September 2, 2022, Belgrad

Photocatalytic efficiency of LiInO2 in degradation of alprazolam from wastewaters

Alprazolam is a widely consumed psychiatric pharmaceutical from the benzodiazepinesgroup, thathas been continuously introduced into the environment throughwastewaters, being a potential risk to living organisms. Furthermore, alprazolam is highly resistant to photodegradation, with degradation half-time of 228 sunny days [1]. Lithium-indium oxide is a high density (5.9 g/cm3 ), wide band-gap semiconductor with promising applications for scintillating detection of solar neutrinos as well as for efficient phosphorescence when doped with different rare earth ions. Here we report for the first time the photocatalytic efficiency of LiInO2 powder, synthesized using a simple solid-state chemistry procedure at relatively low temperature of 700°C. Materials structure was examined by X-ray diffraction,that confirmed materials tetragonal structural form (space group: I41/amd) with no impurity phases. Optical band-gap of 3.99 eV was estimated from the diffuse-reflectance spectrum. Photocatalytic efficiencywas examined under both simulated solar and UV radiation. Photodegradation kineticsshowed LiInO2 powderhas a good potentialfor UV-activated degradation of alprazolam

Photocatalytic efficiency of titanium oxide/molybdite oxide powder mixture

Coupling TiO2 with MoO3 is one of many strategies for the enhancement of titanium oxide photoabsorption under the solar light irradiation. TiO2 being a wide band-gap semiconductor with its unique properties (nontoxicity, photo and chemical stability, and low-cost) is a prominent material for the photocatalytic applications but only when excited by the UV light [1]. Here we report for the first time the photocatalytic efficiency of mixed 2TiO2/MoO3 powders prepared using a simple, mechanochemical solid-state chemistry procedure at a relatively low temperature of 700 °C. Materials structure was examined by means of X-ray diffraction that confirmed the presence of three phases, rutile TiO2, anatase TiO2 and molybdite MoO3 [2]. A unique heterojunction structure with Ti-O-Mo bond between the TiO2 and MoO3 interfaces enables the solar light-driven photocatalytic reaction as well as more efficient separation of the photogenerated electrons and holes for the overall improvement of TiO2 photocatalytic performance. The mixed titanium oxide/molybdite oxide photocatalytic activity was examined under simulated solar irradiation and the experimental photocatalytic kinetics showed that the obtained 2TiO2/MoO3 powder mixture has a good potential for Visactivated degradation of ciprofloxacin, a widely used antibiotic for the treatment of a number of bacterial infections, which is the reason why it was continuously introduced into the environment through wastewaters, and therefore represents a potential risk for the living organisms