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Structural, photoluminescence and thermoluminescence study of novel Li+ co-activated lanthanum oxide activated with Dy3+ and Eu3+ obtained by microwave-assisted solution combustion synthesis
摘要： Stimulated luminescence of novel La2O3 nanophosphors doped with Dy3+ and Eu3+ and co-activated with Li+, prepared by microwave-assisted solution combustion synthesis, was investigated for the very first time. X-ray diffraction results indicated hexagonal La2O3 crystalline phase. Lanthanide and Li+ doping did not affect the La2O3 crystal structure. Scanning electron microscopy images showed nanoparticle morphologies such as plates, rods and irregular shapes. Photoluminescence spectra of La2O3:Dy3+, Li+ exhibited blue and green emission bands due to Dy3+ transitions. For La2O3:Eu3+, Li+, sharp emission lines, corresponding to the optical transitions of Eu3+ were observed. Thermoluminescence glow curve of La2O3:Dy3+, Li+ previously exposed to beta radiation exhibited a prominent glow peak located at ～46 °C, possibly useful for after-glow or persistent luminescence applications, whereas La2O3:Eu3+, Li+ curve, displayed three intense peaks at ～50, ～110 and ～150 °C. Thermoluminescent signal repeatability and decay curve asymptotic behaviour could place La2O3:Eu3+, Li+ as suitable for medium and high-dose radiation dosimetry applications.
关键词： Dosimetry,Thermoluminescence,Solution combustion synthesis,La2O3 co-doped nanoparticles
更新于2025-10-22 19:40:53
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Luminescence properties of Bi doped La2O3 powder phosphor
摘要： Different concentrations of bismuth doped lanthanum oxide (La2-xO3:Bix) phosphor powder (x = 0.001, 0.002, 0.003, 0.004, 0.006, 0.008 and 0.01) were synthesised by means of the sol-gel combustion method at 250 °C using citric acid as the fuel. The product was annealed at different temperatures and the luminescence properties were investigated. The maximum emission was obtained for the sample which was doped with x = 0.002 and annealed at 1200 °C in air. The X-ray diffraction analysis confirmed that all samples crystallized in the La2O3 hexagonal phase. The scanning electron microscopy data showed that the grain size increased with increasing annealing temperature and the shape of the grains changed from rectangular to more round, but faceted, after annealing at 1200 °C in air. Energy dispersive X-ray spectroscopy confirmed the chemical composition, while diffuse reflectance spectroscopy was used to study the absorption of the La2-xO3:Bix samples. All the samples were absorbing in the ultraviolet range between 220 to 320 nm. The band gap of the La2O3 pure host sample was obtained from the reflectance data as 5.1 eV. Excitation at a wavelength of 308 nm resulted in a single broad blue luminescence emission band centered at 462 nm. The excitation and emission bands were attributed to transitions between the 1S0 ground state and the 3P1 excited state of Bi3+ ions, with a Stokes shift of 1.35 eV.
关键词： La2O3,Photoluminescence,Bismuth ions
更新于2025-09-19 17:15:36
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Effect of Bi <sup>3+</sup> ion on upconversion-based induced optical heating and temperature sensing characteristics in the Er <sup>3+</sup> /Yb <sup>3+</sup> co-doped La <sub/>2</sub> O <sub/>3</sub> nano-phosphor
摘要： The upconversion-based optical heating and temperature sensing characteristics are investigated in the Er3+/Yb3+/Bi3+ tri-doped La2O3 nano-phosphor synthesized through a solution combustion method. The structural measurements reveal an increase in lattice parameters and particles size of the phosphor on increasing the concentrations of Bi3+ ions. The energy dispersive spectroscopic (EDS) measurements confirm the presence of La, Er, Yb, Bi and O elements in the tri-doped phosphor. The absorption spectra show the large number of bands due to Er3+, Yb3+ and Bi3+ ions. The Er3+/Yb3+ co-doped phosphor gives strong green emission bands at 523 and 548 nm upon 976 nm excitation due to 2H11/2 / 4I15/2 and 4S3/2 / 4I15/2 transitions of Er3+ ion, respectively. The emission intensity of these bands is enhanced upto 15 times in the presence of Bi3+ ions. The emission intensities of the 523 and 548 nm bands vary non-linearly with the pump power. The fluorescence intensity ratio (FIR) of the thermally coupled 523 and 548 nm emission bands shows efficient optical heating in the tri-doped phosphor. The FIR of the 523 and 548 nm emission bands further varies with the increase in temperature of the phosphor. The relative temperature sensing sensitivity has been calculated to be 71 × 10?4 K?1 at 450 K for the tri-doped phosphor. Thus, the Er3+/Yb3+/Bi3+ tri-doped La2O3 nano-phosphor may provide a platform to use it in the photonic devices, as an optical heater and temperature sensor.
关键词： La2O3 nano-phosphor,temperature sensing,optical heating,solution combustion method,Er3+/Yb3+/Bi3+ tri-doped,upconversion
更新于2025-09-19 17:15:36
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Study on La <sub/>2</sub> O <sub/>3</sub> Wet Clean by pH Controlled Functional Water
摘要： In this paper, we discuss the mechanism as well as the methodology of the La2O3 dissolution and its inhibition by functional waters. To clarify the mechanism, the La2O3 etching behavior in the various solutions, the surface state of La2O3 before and after cleaning, and the impact of functional water process on the electrical properties are evaluated. In order to control the La2O3 dissolution, a functional water process with a CO2 dissolved water as well as an ultra-diluted NH4OH have been developed. As a result of this study, it could be concluded that the pH control of the wet solutions plays an important role in terms of controlling the La2O3 dissolution.
关键词： wet clean,functional water,La2O3,dissolution inhibition,pH control
更新于2025-09-16 10:30:52
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Sol-Gel Derived Dip Coated ZnO – La <sub/>2</sub> O <sub/>3</sub> Thin Film Transistors
摘要： ZnO thin ?lms are fabricated utilizing a cost effective sol-gel dip coating technique and potentially applied as active material in thin ?lm transistors (TFT). The channel length of the TFT is maintained at 40 μm. Thermally deposited high –k La2O3 is used as dielectric material. The fabricated ZnO ?lms are annealed in oxygen atmosphere at 500?C for 1 hour and characterized by XRD, EDX and SEM analysis. The TFTs are fabricated in top gate coplanar electrodes structure on glass substrates. The electrical characteristics of the TFTs are investigated and some important electrical parameters are evaluated. The TFTs exhibit ?eld effect mobility of 1.9 cm2/VS, low threshold voltage of 2.5 Volt, high ON/OFF current ratio of 107, sub-threshold swing of 0.8V/decade, transconductace of 1.2 × 10?3 mho and gain band-width product of 20 kHz.
关键词： ZnO,sol-gel dip coating,thin film transistors,electrical characteristics,La2O3
更新于2025-09-11 14:15:04
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Fabrication of La2O3 Uniformly Doped Mo Nanopowders by Solution Combustion Synthesis Followed by Reduction under Hydrogen
摘要： This work reports the preparation of La2O3 uniformly doped Mo nanopowders with the particle sizes of 40–70 nm by solution combustion synthesis and subsequent hydrogen reduction (SCSHR). To reach this aim, the foam-like MoO2 precursors (20–40 nm in size) with different amounts of La2O3 were first synthesized by a solution combustion synthesis method. Next, these precursors were used to prepare La2O3 doped Mo nanopowders through hydrogen reduction. Thus, the content of La2O3 used for doping can be accurately controlled via the SCSHR route to obtain the desired loading degree. The successful doping of La2O3 into Mo nanopowders with uniform distribution were proved by X-ray photon spectroscopy and transmission electron microscopy. The preservation of the original morphology and size of the MoO2 precursor by the La2O3 doped Mo nanopowders was attributed to the pseudomorphic transport mechanism occurring at 600 ?C. As shown by X-ray diffraction, the formation of Mo2C impurity, which usually occurs in the direct H2 reduction process, can be avoided by using the Ar calcination-H2 reduction process, when residual carbon is removed by the carbothermal reaction during Ar calcination at 500 ?C.
关键词： hydrogen reduction,La2O3,Mo nanopowder,doping,solution combustion synthesis
更新于2025-09-10 09:29:36