Department of Physics

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Influence of Films Thickness on Optical Properties of Nb-Doped TiO2 (NTO) Thin Films Deposited by DC Reactive Magnetron Sputtering
(International Journal of Nano Science and Technology, 2014-01-01) Ollotu, Emmanuel Rasiel; Samiji, Margaret Emmanuel; Kivaisi, Rogath
Transparent conducting oxide (TCO) thin films, particularly sputter-deposited Sn-doped In2O3 (ITO) have a wide application in optical coatings and optoelectronics. However, due to the scarcity and increasing cost of indium, efforts have been done to search for indium-free materials. Sputter-deposited Nb-doped TiO2 (NTO) is among recent materials which have shown great potential for TCO applications. In this study we report and discuss on the influence of films’ thickness on the optical properties of Nb-doped TiO2 (NTO) films deposited on glass substrate from an alloy target of Ti0.99 Nb0.01 (purity 99.9%). It was observed that luminous transmittance (Tlum), solar transmittance (Tsol) and the band gap energy (Eg) increased with increased films thickness while optical constant (n,k) decreased with films thickness. An average Tlum and Tsol of above 60% and a relative increase of IR reflectance were achieved. The results implied a possibility for achieving lowemissivity (low-E) material upon improving the IR reflectance by raising the Nb-doping level.
Impact of North Mara gold mine on the element contents in fish from the river Mara, Tanzania
(Springer Netherlands, 2016-03-08) Mohammed, Najat K.; Ntarisa, Amos V. R; Makundi, Ismael, N; Kučera, Jan
The aim of the study was to determine element concentrations in lungfish and catfish from the river Mara with INAA and EDXF to assess the health impact of the North Mara gold mine (NMGM) in Tanzania. Twenty samples of each species were collected from two sites downstream and upstream along the river Mara in the vicinity of NMGM. The sampling sites were 70 km apart. Significantly higher concentrations (p ≤ 0.05) of Cr, Ni, Cu, and Se in one of the species taken downstream than in those taken upstream might indicate contamination of the river Mara caused by the mining activities.
Status of biomass derived carbon materials for supercapacitor application
(Hindawi, 2017) Enock, Talam Kibona; King’ondu, Cecil K; Pogrebnoi, Alexander; Jande, Yusufu Abeid Chande
Environmental concerns and energy security uncertainties associated with fossil fuels have driven the world to shift to renewable energy sources. However, most renewable energy sources with exception of hydropower are intermittent in nature and thus need storage systems. Amongst various storage systems, supercapacitors are the promising candidates for energy storage not only in renewable energies but also in hybrid vehicles and portable devices due to their high power density. Supercapacitor electrodes are almost invariably made of carbon derived from biomass. Several reviews had been focused on general carbon materials for supercapacitor electrode. This review is focused on understanding the extent to which different types of biomasses have been used as porous carbon materials for supercapacitor electrodes. It also details hydrothermal microwave assisted, ionothermal, and molten salts carbonization as techniques of synthesizing activated carbon from biomasses as well as their characteristics and their impacts on electrochemical performance.
Biogas-slurry derived mesoporous carbon for supercapacitor applications
(Elsevier, 2017) Enock, Talam Kibona; King’ondu, Cecil K.; Pogrebnoi, Alexander; Jande, Yusufu Abeid Chande
This study reports on the transformation of biogas slurry into mesoporous carbon for supercapacitor electrodes. Pore structures have been modified by altering activation time, temperature and KOH/carbon mass ratio. The mesoporous carbons are successively developed as evidenced by type IV isotherms obtained in nitrogen sorption studies. BET, micropore and mesopore surface area of 515, 350, and 165 m2 g−1, respectively as well as a narrow pore width distribution of 3–4.5 nm are obtained. X-ray photoelectron results have confirmed the presence of functional groups of oxygen and nitrogen in the samples which facilitates the pseudocapacitance. The electrochemical measurements in 6 M KOH using a three electrode cell with Ag/AgCl as reference electrode and platinum as counter electrode has been performed. The materials activated at 700 °C, 3:1 KOH to carbon mass ratio, and for 120 min exhibit high specific capacitance of 289 F g−1 at a scan rate of 5 mV s−1. Shortening activation time to 30 and 60 min reduces specific capacitance to 163 and 182 F g−1, in that order. Additionally, at 3:1 KOH to carbon mass ratio and 60 min activation time, specific capacitances of 170 and 210 F g−1 at 600 and 800 °C, respectively are obtained. Moreover, specific capacitance increases with increasing the KOH to carbon mass ratio from 148 F g−1 for 1:1–163 F g−1 for 3:1 at 700 °C. Electrochemical impedance spectroscopy studies demonstrate that material has high conductivity. In addition; capacity retention of 96% after 20,000 cycles is shown at scan rate of 30 mV s−1. The study shows that high performance electrodes can be designed from biogas slurry derived porous carbon.
Hydrogen sulfide and ammonia removal from biogas using water hyacinth-derived carbon nanomaterials
(Academic Journals, 2017) Makauki, Elizabeth; King’ondu, Cecil K.; Kibona, Talam E.
The presence of hydrogen sulfide (H2S) and ammonia (NH3) in biogas pose serious human health and environmental challenges. In this study, H2S and NH3 were successfully removed from biogas using water hyacinth-derived carbon (WHC) nanomaterials. Carbonization temperature, biogas flow rate, mass of the adsorbent and activating agent (KOH/water hyacinth (WH)) ratio were found to greatly influence the efficiency of the H2S and NH3 removal. The adsorption capacity of both H2S and NH3 was found to increase with the carbonization temperature as carbon materials prepared at 450, 550, and 650°C afforded removal efficiencies of 22, 30, and 51% for H2S and 42, 50, and 74% for NH3, respectively, after contact time of 2 h. Similarly, the KOH/WHC ratio showed huge impact on the adsorptive removal of the two species. WH materials carbonized at 650°C and activated at 700°C using 1:4, 1:2, and 1:1 KOH/WHC ratios showed removal efficiencies of 80, 84, and 93% for H2S and 100, 100, and 100% for NH3, correspondingly after 2 h contact time. The adsorption capacity of NH3 increased with the decrease in flow rate from 83 to 100% at flow rates of 0.11 and 0.024 m3/h, respectively, while that of H2S increased from 22 to 93% with flow rate 0.11 and 0.024 m3/h, respectively. The removal of H2S and NH3 increased with adsorbent mass loading. With the 0.05, 0.1, 0.2, and 0.3 g of the adsorbent, the adsorption of H2S after 1.5 h contact time was 63, 93, 93, and 95%, respectively while that of NH3 was 100% for all the adsorbent masses.
Effect of biogas-slurry pyrolysis temperature on specific capacitance
(Elsevier, 2018) Kibona, Talam Enock; King’ondu, Cecil K.; Pogrebnoi, Alexander
The purpose of this study was to investigate the effect of carbonization temperature of biogas slurry on specific capacitance. The biogas derived mesoporous carbon materials were synthesized through carbonization of biogas slurry at 450, 550, and 650 °C followed by activation using KOH at 700 °C for 1 h. The physical characterization done by nitrogen adsorption and desorption, scanning electron microscope, transmission electron microscope and X-ray diffraction shows that pyrolysis temperature has influence on the textural and structural properties of the biogas slurry derived carbon. BET specific surface area of 567, 521 and 499 m2 g-1 were obtained for samples carbonized at 450, 550, and 650 °C, respectively. The electrochemical performance of the samples in 6 M KOH electrolyte exhibited high gravimetric capacitance of 262, 272, and 238 F g-1 for samples carbonized at 450, 550 and 650 °C, correspondingly at scan rate of 5 mV s-1. Moderate carbonization temperature of 550 °C therefore afforded the highest capacitance.
Design of a Low-Cost Underwater LED Fishing Light Attractor
(Scientific Research Publishing; http://www.scirp.org/journal/PaperInformation.aspx?paperID=83920, 2018-04-23) Telemka, Geophrey; Mghamba, Mariana; Ntarisa, Amos
Fishermen generally use light as a common way to attract fish in the fishing industry. This study aimed to design a model of an underwater fishing using Light Emitting Diode (LED) lamp which is less costful and suitable for fishermen of Tanzania. Most fishermen currently use kerosene based lamps like candela which consumes lots of energy leading to high cost in terms of money used to regenerate the energy. This running cost automatically rises up the price of fish in the market. Thus with the use of LED lamp the cost will be reduced. The findings from this study showed that the LED lamp consumes little amount of energy (energy saving) compared to candela lamp which consumes 6 liters of kerosene per 36 hours which is equivalent to three nights, while the LED lamp takes 7 batteries at once for 36 hours. The 6 liters of kerosene cost around 7 USD and that of 7 batteries cost is near 2 USD. The LED lamp can be accessed by only 15 USD the price which is nearly half the price of the candela lamp. The candela lamp in the market is sold around 31 USD. This shows that LED lamp is more efficient in terms of conserving energy and cost effective than candela lamp. It is recommended that fishermen in the fishing industry in Tanzania should employ the usage of underwater LED fishing lamps as they are energy efficient. This will help the fishermen of Tanzania to undertake the fishing activity at low cost which will result to the decrease of price of fish in the market. This shows that this LED lamp has high efficiency and effectiveness to be used by fishermen compared to traditional method used by majority of them.
ASSESSMENT OF INDOOR RADON-222 CONCENTRATIONS IN THE VICINITY OF MANYONI URANIUM DEPOSIT, SINGIDA
(Tanzania Journal of Science, 2018-05-23) Mlay, Germana; Makundi, Ismael
This study aimed to assess indoor radon concentrations in the vicinity of the Manyoni Uranium Deposit in Singida. The concentrations were measured for two months in 32 houses in the vicinity of Manyoni Uranium Deposit and 9 houses at Manyoni town using a portable radon gas monitor (Alpha –GUARDTM). The radon concentrations ranged from 27±3 to 518±28 Bq/m3with the overall mean of 166±12 Bq/m3 which is above recommended values of 100 Bq/m3 and 148 Bq/m3 set by WHO (World Health Organization) and EPA (Environmental Protection Agency's), respectively. The overall mean of indoor radon concentrations from each village were Kipondoda (169±13 Bq/m3), Muhalala (177±16 Bq/m3), Mwanzi, (287±13 Bq/m3), Mitoo (325±21 Bq/m3) and Majengo (377±23 Bq/m3) which exceed the limit set by WHO (World Health Organization) and EPA (Environmental Protection Agency). The value of 325±21 Bq/m3 and 377±23 Bq/m3 from Mitoo and Majengo respectively, exceed the limit of 300 Bq/m3 recommended by ICRP (International Commission on Radiation Protection). Thus there is a non-negligible probability of incurring stochastic effects for people living in the vicinity of Manyoni Uranium mine. It is recommended that human activities should be controlled near the uranium deposits and dwelings should be well ventilated.
Porous carbon derived from Artocarpus heterophyllus peels for capacitive deionization electrodes
(Elsevier, 2019) Elisadiki, Joyce; Jande, Yusufu Abeid Chande; Machunda, Revocatus Lazaro; Kibona, Talam Enock
Sustainable clean water for human use can be attained through cost effective water purification technologies where by capacitive deionization (CDI) technology is among them. To attain high CDI performance porous carbon materials with good electrical conductivity, high surface area, specific capacitance and good chemical stability are essential. In this study high surface area porous carbon has been synthesized through carbonization of agricultural waste jackfruit peels (Artocarpus heterophyllus) followed by KOH activation at 600, 700, and 800 °C for 1 h. It was found that, the activation temperature significantly increased the BET surface area of the synthesized carbon from 607 m2/g to 1955 m2/g. Desalination experiments were carried out with 30–500 mg/L NaCl solution in batch mode at a flow rate of 2.5 ml/min while applying voltage of 1.2, 1.4 and 2.0 V to the cell. The electrosorption capacity and salt-removal efficiency increased with increasing BET Surface area and applied potential. Specifically, ACJF1:1-700 exhibited highest specific capacitance of 307 F/g, high salt removal efficiency and electrosorption capacity of 5.74 mg/g when voltage of 2 V was applied. These results indicated that the Artocarpus heterophyllus can be promising CDI electrode materials for low salinity water desalination.
Fish bladder-based activated carbon/Co3O4/TiO2 composite electrodes for supercapacitors
(Elsevier, 2019) Sirengo, Keith; Jande, Yusufu Abeid Chande; Kibona, Talam Enock; Hilonga, Askwar; Muiva, Cosmas; King'ondu, Cecil K
Cobalt oxide/titanium dioxide/activated carbon (Co3O4/TiO2/Ac) composite was synthesized using simple sol-gel method before annealing at 300 °C. Fish bladder derived porous carbon used for the composite was synthesized by pyrolysis followed by chemical activation. Both scanning electron microscopy (SEM) and X-ray diffraction displayed Co3O4 and TiO2 phases well embedded onto the carbon matrices. Cyclic voltammetry in 6 M KOH electrolyte demonstrated that the composite has an excellent specific capacity of 946 Fg-1 for Co3O4/TiO2/Ac as compared to Co3O4/Ac, TiO2/Ac, and Ac with specific capacitances of 845, 340, and 308 F g−1, respectively at 5 mVs−1. Impedance spectroscopy reveals that the composite has good capacitive behavior with a series resistance of 0.6 Ω. Besides, Co3O4/TiO2/Ac maintains 89.7% of the initial capacitance after 2000 cycles. This study shows that the synergistic effect of the metal oxides and the carbon in the composite can enhance capacitance for practical supercapacitor applications.
Specific capacitance–pore texture relationship of biogas slurry mesoporous carbon/MnO2 composite electrodes for supercapacitors
(Elsevier, 2019-02) Kibona, Talam Enock; Shao, Godlisten N.; Kim, Hee Taik; King’ondu, Cecil K.
Here, we report synthesis of biogas slurry mesoporous carbon/MnO2 composites by simple co-precipitation route followed by thermal treatment at 250 °C for 6 h. The texture, morphology, crystal structure, and microstructure of the composites are investigated by nitrogen sorption studies, FESEM, HRTEM, X-ray diffraction, and Raman spectroscopy. All samples exhibit type IV isotherms. The BET surface area decreased from 514 to 110 m2 g−1 while total pore volume decreased from 0.52 to 0.17 cm3 g−1 for samples loaded with 2×10−5 and 2×10−3 moles of Mn. The electrodes fabricated exhibit high specific capacitance of 709 F g−1 at scan rate of 5 mV s−1. The specific capacitance at scan rate of 5 mV s−1 increases with increasing MnO2 content. However, at 50 mV s−1, specific capacitance decreases with increasing MnO2 content. Varying the MnO2 content and hence the textural parameters, strongly influences the specific capacitances of the composite electrodes.
Biomass-based carbon electrode materials for capacitive deionization: a review
(Springer, 2019-06-27) Elisadiki, Joyce; Kibona, Talam Enock; Machunda, Revocatus L.; Saleem, Muhammad Wajid; Kim, Woo-Seung; Jande, Yusufu A. C.
Capacitive deionization (CDI) is a promising water purification technology which works by removing salt ions or charged species from aqueous solutions. Currently, most of the research on CDI focuses on the desalination of water with low or moderate salt concentration due to the low salt adsorption capacity of the electrodes. The electrosorption capacity of CDI relies on the structural and textural characteristics of the electrode materials. The cost of electrode materials, the complicated synthesis methods, and the environmental concerns arising from material synthesis steps hinder the development of large-scale CDI units. By considering the good electrical conductivity, high specific surface area (SSA), porous structure, availability, mass production, and cost, porous carbon derived from biomass materials may be a promising CDI electrode material. This review presents an update on carbon nanomaterials derived from various biomasses for CDI electrodes. It covers different synthesis methods and the electrosorption performance of each material and discusses the impact of the SSA and porous structure of the materials on desalination. This review shows that a variety of biomass materials can be used to synthesize cost-effective CDI electrode materials with different structures and good desalination performance. It also shows that diverse precursors and synthesis routes have significant influences on the properties and performance of the resulting carbon electrodes. Additionally, the performance of CDI does not depend only on BET surface area and pore structure but also on the applied voltage, initial concentration of the feed solution, and mass, as well as the capacitance of the electrodes.
Highly microstructured porous carbon derived from vitex mombassae for high specific capacitance supercapacitors
(Spinger, 2019-08-26) Kibona, Talam Enock
This study reports on producing highly porous carbon materials by carbonization and activation of biomass (Vitex mombassae) seed wastes. The pore textural properties and microstructures of the synthesized materials are controlled by adjusting the activation temperature from 600 to 800 °C. X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, Raman and nitrogen adsorption and desorption are used to study the physical characteristics of the synthesized materials. The Brunauer–Emmet–Teller surface area, micropore surface area and pore volume increase with activation temperature. At activation temperature of 700 °C, the porous carbon acquires high specific area (2044 m2 g−1). The pore volume increases with increase in activation temperature 0.8–1.1 cm3 g−1 with high self-doping oxygen content. As a result of good physical characteristics, the prepared electrodes exhibit excellent performance with the specific capacitance up to 437 F g−1 at 5 mV s−1 in 6 M KOH electrolyte. The good capacitive behavior of the synthesized porous carbon depends on high surface area, micropore pore volume as well as moderate microstructures. The synthesized sample demonstrates high cyclic stability with capacitance retention of over 90% after 50,000 cycles.
Mesoporous Electrodes for Supercapacitors
(CRC Press (Taylor & Francis Group), 2019-12) Shao, Godlisten N.; Kibona, Talam Enock
Mesoporous electrodes with desirable properties for supercapacitors are very fascinating and their ubiquitous attraction to scientists and engineers is indisputably incessant. Conversely, supercapacitors are highly researched energy storage materials due to their promising potentials to solve the energy storage demands for high-performance energy applications. Investigation of materials with suitable properties for mesoporous electrodes for supercapacitors is mainly carried out to improve their power density and energy density. This chapter highlights the recent investigations and advances toward the development of mesoporous electrodes for supercapacitors.
Highly porous biomass-based capacitive deionization electrodes for water defluoridation
(2019-12-09) Elisadiki, Joyce; Jande, Yusufu; Kibona, Talam Enock; Machunda, Revocatus
The high concentration of fluoride (F−) in water sources is the main challenge in major fluoride belts. Though capacitive deionization (CDI) with porous carbon electrodes is the promising alternative in removing charged species from aqueous solution, little has been presented on the usefulness of CDI with biomass-based electrodes in removing F− from natural water existing together with other ions such as Ca2+ and Mg2+. This study investigated the feasibility of using biomass-based electrodes for natural water defluoridation application. Porous carbon was synthesized from jackfruit peels (JFAC) through potassium hydroxide (KOH) activation. Surface morphology, pore structure, and electrochemical properties of the JFAC were investigated. The textural properties of the synthesized carbon and electrochemical characteristics of the fabricated electrodes were found to be influenced by activation temperature. Brunauer-Emmett-Teller (BET) surface area, pore diameter, pore volume, and pore surface area increased with an increase in activation temperature and KOH to carbon ratio. It was further confirmed that as the applied voltage increased from 1.2 to 2 V, the amount of adsorbed anions increased without significantly affecting the pH of the water. At 2.0 V, the electrodes showed a maximum F− adsorption efficiency and electrosorption capacity of 62% and 0.13 mg/g respectively. The electrosorption capacity depends on the initial concentration of the ion in the feed water. It was further observed that natural organic substances contained in the natural water might inhibit JFAC electrode surface and decrease its adsorption efficiency. This study provides cost-effective CDI electrode material prepared from biomass for water defluoridation.
Synthesis of NiCo2O4/mesoporous carbon composites for supercapacitor electrodes
(Springer, 2020) Kibona, Talam Enock
In this study, nickel cobaltite/mesoporous carbon composites are synthesized by reacting CoCl2, Ni (NO3)2 and nitric acid-treated biogas slurry mesoporous carbon using urea as hydrolyzing agent and hexadecyltrimethylammonium bromide (CTAB) as surfactant. The presence of Ni, Co, C and O peaks in the EDX results confirm that the composites are successfully synthesized. Interestingly at 350 °C, the composite surface morphology switched to cross-linked nanoflake structures interconnected with mesoporous carbon. The X-ray diffraction analysis of the NiCo2O4/mesoporous carbon composites reveals that the spinel structure of the NiCo2O4 is maintained in the composites. The nitrogen uptake increases with increasing annealing temperature to 300 °C then decreases at higher temperature (400 °C). The type IV isotherms are exhibited by all the composites. The contribution of mesopores increases with increasing annealing temperature: 32% for BC-NCo-200, 41% for BC-NCo-250, 56% for BC-NCo-300, 66% for BC-NCo-350 and 86% for BC-NCo-400. The NiCo2O4/mesoporous carbon composites exhibit high specific capacitance of 835 F g−1 at scan rate of 5 mV s−1 for sample annealed at 350 °C. The cyclic stabilities of the electrodes are above 90% after 50,000 cycles indicating that the synthesized composites are suitable candidates for supercapacitors.
Application of WRF Mesoscale Model for Prediction of Wind Energy Resources in Tanzania
(Elsevier, 2020-01-30) Kibona, Talam Enock
This study gives an overview of the wind energy resource distribution within and of the coast of Tanzania. Wind speed predictions using WRF model at 60 m a.g.l, which is typically the height of turbine hub, are compared with the wind speed values obtained by extrapolating Final Analysis (FNL) wind speed data at 10m a.g.l using power law. The WRF Model is used for 72-hours wind speed and direction forecasting where the initial boundary of the model is provided by Final Analysis data (FNL) available at UCAR with resolution of 1 × 1 degree. The WRF model has good results in comparison to power law because the variation is very small. At 1200 and 1800 hours over the areas near the land WRF predicts low wind speed than power law. WRF model predicts more offshore wind strength in the night than the noon. At 1300 to 1400 hrs the wind speed in the offshore part of Tanzania is mostly below 9 m/s as predicted by WRF model. Based on the limited studies, it has been observed that the wind energy potential exists in the offshore zones of Tanzania. This study encourage exploring the possibilities of harnessing the offshore wind energy potentials available in Tanzania. The approach adopted could be configuring WRF models with high horizontal resolution and many domains and carrying out detailed theoretical assessment of the wind energy resources, supplemented by actual measurements of the wind pattern using met-masts at different locations across and offshore of Tanzania.
Highly mesoporous Parinari Curatellifolia carbon nanomaterials for supercapacitors
(Elsevier, 2020-04-01) Kibona, Talam Enock; Achola, Laura; Kerns, Peter; Macharia, John; King'ondu, Cecil K; Suib, Steven
High surface area nanostructured electrodes are essential for understanding charge storage mechanisms in high capacitance supercapacitors. Additionally, a growing number of studies provide credible evidence that the highest capacitance in carbon nanomaterials is attainable only when the pore size is in micropore range. In this study therefore, micropore-dominatedcarbon materials derived from Parinari curatellifolia (PC) waste seeds are prepared via pyrolysis and subsequent chemical activation with KOH. SEM, EDAX, TEM, Raman, and XRD studies show that the microstructure and composition of the as-prepared microporous carbon materials are influenced by adjusting the KOH to carbon mass ratio. Sorption studies demonstrate a very high BET surface area of 1898 m2 g−1, type I isotherm, and 99% micropore content in all the samples. The BET surface area, S, V, and total volume increased with increasing KOH content during activation. The fabricated electrodes exhibit high specific capacitances of 423 F g−1 at 5 mV s−1 and cyclic stability of 98% after 50000 cycles both of which are indicative of our carbon materials huge potential in making high performance supercapacitors. The specific capacitance increased with the micropore content in the samples signifying that the pores enhanced diffusion and hence the charge storage. The PC carbon materials deliver high specific capacitance due to the enhancement of diffusion and charge storage stemming from the synergetic interplay of the aforementioned textural parameters. The PC carbon materials therefore provide good prospects for supercapacitor applications.
A novel blue-emitting phosphors (CsBaYB6O12:Ce3+): Potential applications in w-LEDs and X-ray phosphors
(Elsevier, 2021-08-25) Ntarisa, Amos Vincent; D Joseph, Daniel; D, Balaji; Raja, Arumugam; Kim, HongJoo; Nguyen, Duy Quang
We have synthesized powder samples of pure and Ce3+ doped cesium barium yttrium hexaborate (CsBaYB6O12) using a standard solid-state reaction technique. The prepared samples were characterized by different techniques. Powder X-ray diffraction (PXRD) was used to identify the phase purity of the prepared phosphors. The field emission scanning electron microscopy (FE-SEM) technique was used to examine the size and shape of the synthesized powder samples. The energy-dispersive spectral analysis (EDS) was used to identify the elements present in the synthesized compounds. X-ray-induced luminescence spectra, photoluminescence (PL), and thermoluminescence (TL) analysis were used to investigate the luminescence properties of the prepared compound. The rare earth ion of Ce3+ improves the intrinsic luminescence of CsBaYB6O12 and 4 mol% was found to be the optimal concentration. The dopants found to have two different excitation PL bands at 340 nm and 360 nm which yields the same emission bands of 385 and 417 nm which are well-matched with that found in the X-ray emission bands. The kinetic parameters of the measured experimental TL glow curve has been studied by various standard methods such as deconvolution, Variable heating rate and initial rise method. In this manuscript we report the luminescence properties of the prepared phosphors in a detailed manner for the first time.
Luminescence and scintillation properties of Ce3+-doped P2O5-Li2CO3-GdBr3-Al2O3 glasses
(Elsevier, 2021-09-01) Ntarisa, Amos Vincent; Saha, Sudipta; Aryal, Pabitra; Kim, HongJoo; Khan, Arshad; Nguyen, Duy Quang; Pandey, Indra Raj; Kaewkhao, Jakrapong; Kothan, Suchart
A series of glass samples were fabricated with the composition of (65-x)P2O5:20Li2CO3:10GdBr3:5Al2O3:xCeBr3 (where, x = 0.5,1,2,3,4). The powder X-ray diffraction measurements were performed to verify the amorphous structure of the prepared glass samples. Energy-dispersive X-ray spectroscopy showed an interesting phenomenon of oxygen bridging eliminating Br (Bromine) from the initial compounds. The luminescence characteristics of the samples were studied using X-rays and UV–Vis excitations. Characteristics Ce3+ emission was observed at 350 nm including energy transfer from 4f energy state of Gd3+ to 5d energy band of Ce3+. The fast decay component was observed as 37 ns, 42 ns, and 44 ns for the UV, α-particles, and γ-ray excitations, respectively. The intermediate and slow components were observed for α-particles, and γ-rays excitations indicating Gd3+ to Ce3+ energy transfer and 4f-4f transitions of Gd3+ -ions accordingly. The scintillation property was studied with α-particles using a 241Am source.

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