BETZABEL N. S. CARRERA

BETZABEL N. S. CARRERA

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Study of the centers responsible for the TL emission by EPR and PL analysis of Eu-doped CaSiO3 phosphors synthesized by the devitrification method
2024 - GONZALES-LORENZO, CARLOS D.; GUNDU RAO, T.K.; CCOLLQUE-QUISPE, ALBERTO A.; AYALA-ARENAS, JORGE; GOMES, MONISE B.; SILVA-CARRERA, BETZABEL N.; GENNARI, ROSELI F.; PACHAS, VALERIA S.; MONZON-MACEDO, F.; LORO, H.; CHUBACI, JOSE F.D.; CANO, NILO F.; ROCCA, RENE R.; WATANABE, SHIGUEO
CaSiO3 doped at different ppm of Eu were synthesized by the devitrification method. Polycrystals exhibit a prominent high-temperature TL peak that increases in intensity and shifts toward higher temperatures with increasing amounts of dopant. TL emission spectrum of CaSiO3: Eu displays two very broad bands centered at 400 and 440 nm corresponding to the temperatures of 229.5 and 373.5 degrees C, respectively. PL measurements indicate the presence of Eu2+ and Eu3+ ions. EPR spectrum arises from two defect centers. One of the centers with principal g-values 2.016, 2.0091, and 2.0051 is attributed to O- ion and the center correlates with the TL peak at 236 degrees C. Center II with an isotropic g-value of 2.0018 is attributed to an F+ center and the center relates to the TL peak at 120 degrees C. Center III is also tentatively identified as the F+ center which is associated with the TL peak at 365 degrees C.
Effects of eletromagnetic radiation of different energies in blue quartz - thermoluminescence dosimetry
2023 - SILVA-CARRERA, N.B.; NILO F.C.M.; CRUZ, SOFIA P.S.; CHUBACCI, J.F.D.; WATANABE, S.
Quartz, which is the second most abundant mineral in the continental crust, is found in igneous, metamorphic and sedimentary rocks, and it belongs to the silica group, which has SiO2 as its basic composition. The quartz phase presents modifications of the α and β types, being that α-quartz is stable for temperatures below 573 °C and crystallizes trigonally, and β-quartz system is stable in between 573 °C – 870 °C and crystallizes in a hexagonal structure. Its symmetry class is 32, which means it presents structural enantiomorphism. The difference in electronegativity between oxygen and silicon creates covalent bonding (40%) as well as ionic bonding (60%). The objective of this present work is to study the dosimetric properties of blue quartz such as its reproducibility, repeatability, linearity, signal fading, and energy dependence, for its possible use as a thermoluminescent dosimeter. The natural blue quartz, purchased at the LEGEP stone store in São Paulo, was pulverized with a mortar and pestle, both made of high-hardness ceramic; the sample was then sieved to select for grains measured between 80 µm and 180 µm in diameter, and grains smaller than 80 µm were used for X-ray diffraction and X-ray fluorescence. In the powder sample, measurements were done of the thermoluminescence readings of the sample in natura, as well as of the dependence of the dose to the TL response. The blue quartz grains were sensitized using two methods: heat treatment and pre-dosing, to thus obtain the best combination of synthesis temperature, sensitization dose and activation temperature. The TL glow curve of the quartz in natura shows the TL peaks, the first being around 200 °C and the second at around 325 °C. The 325 °C peak is widely used in dating works (CANO, et al., 2015; VICHAIDIS and SAEINGJAEW, 2022; GU, et al., 2021). The selected grains were separated into packages, and irradiated with increasing doses of gamma radiation from 50 Gy to 3 kGy, and, in the emission curves obtained, it is possible to observe the TL peaks around 121 °C, 169 °C, 203 °C, 257 °C and 342 °C. Peaks below 190 °C are considered unstable in dosimetry because they disappear within a few hours, and peaks above 190 °C are considered stable peaks. For the thermal treatment method, blue quartz grains were thermally treated at 400 °C, 600 °C, 800 °C, 1000 °C and 1200 °C, followed by a rapid cooling, and then irradiated with a dose of 1 Gy. It was observed that, for the temperature of 600 °C, the emission curve presents two peaks, at 150 °C and 350 °C; for 800 °C, peaks appear around 140 °C, 204 °C and 340 °C; for the thermal treatment at 1000 °C, 2 peaks can be observed at 140 °C and 200 °C, and the peak of 340 °C is not observed; and for the treatment of 1200 °C, the TL emission curve presents a well-defined peak around 204 °C. For the pre-dosing method, eight different pre-doses between 50 Gy and 20 kGy were tested, and it was found that the blue quartz sample with a pre-dose of 500 kGy has the highest TL intensity value, and, beyond that dose, the response begins to decrease. Thus, the pre-dose of 500 Gy was chosen for testing different values of thermal activation, in which the quartz grains, after being irradiated with the pre-dose of 500 Gy, were thermally treated with temperatures of 300 °C, 400 °C , 500 °C, 550 °C, 600 °C, and 650 °C for one hour, and then irradiated with a test dose of 1 Gy. It was observed that, for 550°C, the TL intensity is maximum, and, beyond that temperature, the TL intensity begins to decrease, due to thermal deactivation occurring. Blue quartz pellets have thermoluminescent properties that make them suitable for gamma radiation dosimetry. The TL emission glow curve of the material was reproduced with the GlowFit program, showing that the curve is composed of six peaks. The linearity of the TL response was proven for up to 5 Gy, and, beyond that, it then presents a sublinear behavior. The minimum detectable dose for the pellets studied is 2.34 mGy, and the TL peak at 221 °C has less than 5 % fading, indicating that this peak can be used for dosimetry. In conclusion, blue quartz pellets can be used as passive dosimeters in gamma radiation applications, and their thermoluminescent properties have been well studied and characterized.
Luminescence dating and firing temperature determination of ancient ceramics fragments from the Tunata-hill site in the Churajon archaeological complex in Arequipa, Peru
2023 - PACOMPIA, YOLANDA; SUPO-RAMOS, JUSTO G.; GONZALES-LORENZO, CARLOS D.; CALLO-ESCOBAR, DARWIN J.; ROCCA, RENE R.; PASTRANA, ELIZABETH C.; GOMES, MONISE B.; SILVA-CARRERA, BETZABEL N.; WATANABE, S.; AYCA-GALLEGOS, OSCAR; AYALA-ARENAS, JORGE S.
Ancient pottery fragments from the Tunata-hill site in Churajon archaeological complex, Arequipa, Peru, were dated by means of luminescence techniques such as thermoluminescence (TL) and optically stimulated luminescence (OSL) in order to provide absolute chronology. For TL, additive and regenerative methods were performed. For OSL a regenerative method was carried out for IRSL dating. A rigorous description of the study area and its context has been made. The ages of the samples were found to be between 0.50 ± 0.06 ky and 0.49 ± 0.03 ky for TL methods, and 0.49 ± 0.02 ky for OSL methods. On average, the estimated age by TL and OSL techniques is 490 ± 70 yr (1600 AD and 1460 AD). This means that Churajon ceramics under study would belong to the Late periods which corresponds to the Inca region, and the North sub-region of the Late Churajon phase, and the beginning of European colonization in Peru. X-ray fluorescence technique (XRF) analysis has shown the main presence of Fe (39.5%), Si (30.0%), and Al (10.4%) in fine pottery powder. Furthermore, the electron paramagnetic resonance (EPR) technique was used to study the firing temperature using the iron signal (Fe3+) as a firing temperature reference. The firing temperature of ceramics was found to be around 550 ± 50 °C.
Preparation and study of the main dosimetric properties by TL of sintered lithium silicate pellets
2023 - CANO, NILO F.; AYNAYA-CAHUI, SANDRA C.; VILCA, ZAIDA V.; ROCCA, RENE R.; GUNDU RAO, T.K.; CARRERA, BETZABEL N.S.; LOPEZ-GONZALES, ALEJANDRO H.; JAVIER-CCALLATA, HENRY S.; AYALA-ARENAS, JORGE S.
This work presents the structural characteristics and the dosimetric properties under ionizing radiation of the lithium silicate (LSO) (LSO) phosphor. The structure of the synthesized material was determined by X-ray diffraction (XRD) method and Rietveld refinement method. The dosimetric properties of LSOLSO in the form of pellets were studied by thermoluminescence (TL) under the effect of different doses of γ-irradiation. The phosphor exhibited a TL emission curve with four TL peaks centered at 100, 182, 250 and 290 °C, with a light emission band centered at 385 nm. The TL dose-dependent γ-radiation dose response of the TL peak at 182 °C was linear in the low-dose region, from the order of mGy to 50 Gy. In addition, the phosphor exhibits lower fading, good reproducibility, and sensitivity of the order of commercial TLD-100 dosimeters.
Thermoluminescence and defect centers in β-CaSiO3 polycrystal
2020 - GONZALES-LORENZO, CARLOS D.; GUNDU RAO, T.K.; CANO, NILO F.; CARRERA, BETZABEL N.S.; ROCCAB, RENE R.; CUEVAS-ARIZACA, EDY E.; AYALA-ARENAS, JORGE S.; WATANABE, SHIGUEO
β: CaSiO3 polycrystal was synthesized by the devitrification method. The polycrystal exhibits three thermoluminescence (TL) peaks at 124 ºC, 250 ºC and 306 ºC. Electron paramagnetic resonance (EPR) spectroscopy was used to study the defect centers induced in the polycrystal by gamma irradiation and to identify the centers responsible for the TL process. Three defect centers contribute to the observed spectrum at room temperature. Center I with principal g-values 2.0135, 2.0094 and 2.0038 is attributed to O ion and the center appears to be the recombination center for 124 ºC, 147 ºC and 306 C TL peaks. Center II exhibiting an isotropic g-value of 2.00025 is identified as an Fþ-center (singly ionized oxygen vacancy). Fþ-center is also observed to be a recombination center for several TL peaks. Center III is assigned to a Ti3þcenter displaying an orthorhombic g- tensor with principal values g1 ¼1.9830, g2 ¼1.9741 and g3 ¼1.9046. This center is associated with 124 ºC and 147 ºC TL peaks. TL emission spectrum of β-CaSiO3 shows two emission bands at 370 and 520 nm.
Low dose radiation dosimetry using natural blue quartz crystal by TL technique
2018 - SILVA-CARRERA, BETZABEL N.; CANO, NILO F.; WATANABE, SHIGUEO