Sol-gel produced Zn2V2O7 phosphors’ improved luminous properties: The role of thermal treatment
- Authors: Dejene, Francis Birhanu
- Date: 2023/02
- Subjects: Vanadate , Annealing , Crystallinity , Thermogravimetric , Photoluminescence
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/11260/13220 , vital:78106 , DOI: https://doi.org/10.1016/j.heliyon.2023.e13878
- Description: Zn2V2O7 phosphor was made using a sol-gel technique and then annealed at temperatures ranging from 700 to 850 ◦C. The x-ray diffraction (XRD) results revealed that Zn2V2O7 exhibits a single monoclinic phase. The width at half-maximum of the (022) XRD peak shrank overall resulting in improved crystallinity of the Zn2V2O7 phosphors with higher annealing temperatures. Because of the good crystallinity of Zn2V2O7, scanning electron microscopy (SEM) indicates that grain size increases as the annealing temperature rises. When the temperature was raised from 35 ◦C to 500 ◦C, TGA findings revealed a total weight loss of approximately 65%. The photoluminescence emission spectra of annealed Zn2V2O7 powders revealed a wide green-yellowish emission in the range of 400 nm–800 nm. As the annealing temperature was raised, the crystallinity improved, resulting in an increase in PL intensity. The peak of the PL emission shifts from green to yellow emission.
- Full Text:
- Authors: Dejene, Francis Birhanu
- Date: 2023/02
- Subjects: Vanadate , Annealing , Crystallinity , Thermogravimetric , Photoluminescence
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/11260/13220 , vital:78106 , DOI: https://doi.org/10.1016/j.heliyon.2023.e13878
- Description: Zn2V2O7 phosphor was made using a sol-gel technique and then annealed at temperatures ranging from 700 to 850 ◦C. The x-ray diffraction (XRD) results revealed that Zn2V2O7 exhibits a single monoclinic phase. The width at half-maximum of the (022) XRD peak shrank overall resulting in improved crystallinity of the Zn2V2O7 phosphors with higher annealing temperatures. Because of the good crystallinity of Zn2V2O7, scanning electron microscopy (SEM) indicates that grain size increases as the annealing temperature rises. When the temperature was raised from 35 ◦C to 500 ◦C, TGA findings revealed a total weight loss of approximately 65%. The photoluminescence emission spectra of annealed Zn2V2O7 powders revealed a wide green-yellowish emission in the range of 400 nm–800 nm. As the annealing temperature was raised, the crystallinity improved, resulting in an increase in PL intensity. The peak of the PL emission shifts from green to yellow emission.
- Full Text:
Combustion synthesis of nanocrystalline Ba1.3Ca0.7SiO4 semiconductors using urea as an energy efficient fuel
- Golja, Desta R, Dejene, Francis B
- Authors: Golja, Desta R , Dejene, Francis B
- Date: 2023/01
- Subjects: Silicate , Urea , Metal oxide , Photoluminescence , Solution combustion synthesis
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/11260/13179 , vital:78007 , DOI: https://doi.org/10.3390/inorganics11020048
- Description: The τ-phase Ba1.3Ca0.7SiO4 alkaline earth silicate powders were synthesized using the solution combustion technique. For this purpose, metal nitrate–urea mixtures were used as anoxidant and a fuel. Urea’s main function was to help lower the nominal combustion temperature (~550 ◦C) of the mixtures through exothermic reactions, leading to a relatively mild post-annealing temperature (~750 ◦C). If the urea concentration increased, the interconnected silicate particle size decreased with nanoscale crystallite (average, 33 ± 3 nm), affecting optical properties. Finally, the photoluminescence spectra suggested that the light emission was through trap sites, because the emitted blue and green lights (2.6 and 2.3 eV, respectively) were smaller than the bandgap (~3.2 eV) of the Ba1.3Ca0.7SiO4 semiconductor.
- Full Text:
- Authors: Golja, Desta R , Dejene, Francis B
- Date: 2023/01
- Subjects: Silicate , Urea , Metal oxide , Photoluminescence , Solution combustion synthesis
- Language: English
- Type: Article
- Identifier: http://hdl.handle.net/11260/13179 , vital:78007 , DOI: https://doi.org/10.3390/inorganics11020048
- Description: The τ-phase Ba1.3Ca0.7SiO4 alkaline earth silicate powders were synthesized using the solution combustion technique. For this purpose, metal nitrate–urea mixtures were used as anoxidant and a fuel. Urea’s main function was to help lower the nominal combustion temperature (~550 ◦C) of the mixtures through exothermic reactions, leading to a relatively mild post-annealing temperature (~750 ◦C). If the urea concentration increased, the interconnected silicate particle size decreased with nanoscale crystallite (average, 33 ± 3 nm), affecting optical properties. Finally, the photoluminescence spectra suggested that the light emission was through trap sites, because the emitted blue and green lights (2.6 and 2.3 eV, respectively) were smaller than the bandgap (~3.2 eV) of the Ba1.3Ca0.7SiO4 semiconductor.
- Full Text:
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