L. Fornaro

Crystallization as a way for inducing thermoluminescence in a lead borate glass

A great improvement in thermoluminescence response was found, for the first time, for crystallized samples of lead borate glass of composition 33% PbO and 67% B2O3 (% in mol); this response clearly increases with crystallization time. Glass–crystal transformation was characterized by thermal analysis and by scanning electron microscopy. Results indicate the studied lead borate glass–ceramic as a promising material for thermoluminescence dosimetric applications.

Nanoparticles for nucleation of heavy metal iodide films: Mercuric iodide and bismuth tri-iodide cases

Mercuric iodide and bismuth tri-iodide nanoparticles were synthesized by suspension in octadecene, from Hg(NO<inf>3</inf>)<inf>2</inf>. H<inf>2</inf>O and I<inf>2</inf>, and from Bi(NO<inf>3</inf>)<inf>3</inf>. 5H<inf>2</inf>O and I<inf>2</inf>, respectively. The best synthesis conditions were 2 hrs. at 60–70 ºC, followed by 10 min. at 95–110 ºC for mercuric iodide nanoparticles, and 4 hrs. at 80–110 ºC, followed by 10 min. at 180–210 ºC for bismuth tri-iodide ones. Nanoparticles were then washed and centrifugated with ether repeatedly. Compounds identity was confirmed by X-ray diffraction (XRD) and energy dispersive spectrometry (EDS). Nanoparticles were characterized by transmission (TEM) and scanning (SEM) electron microscopy. Disk-like and squared mercuric iodide nanostructures were obtained, 80–140 nm and 100–125 nm in size respectively. Rounded and rod-like bismuth tri-iodide nanoparticles, 30–500 nm in size were obtained. Acetonitrile and isopropanol suspensions of mercuric iodide nanoparticles, and acetonitrile suspension of bismuth tri-iodide nanoparticles exhibited peak maxima shifts in their UV-Vis spectra, as was reported for nanoparticles of other materials. It is the first time that mercuric iodide and bismuth tri-iodide nanoparticles are synthesized by the suspension method, although uniform shape and size distributions have not yet been obtained. They offer interesting perspectives for crystalline film nucleation, for improving current applications of these materials, as far as for opening new ones.

Influence of solvothermal synthesis conditions in BiSI nanostructures for application in ionizing radiation detectors

BiSI belongs to the A V B VI C VII chalcohalides group of compounds. These compounds show several interesting properties such as ferroelectricity, piezoelectricity along the c axis, and photoconductivity. Moreover, BiSI is a potential semiconductor material for room-temperature gamma and x-ray detection, given its band gap of 1.57 eV and its high density, 6.41 g cm−3. In this work we present BiSI nanostructures synthesized by the solvothermal method with the intention of using them for ionizing radiation detection. The solvent was varied to study its influence in morphology, particle size and size distribution. Three different conditions were tested, using either water, monoethylene glycol and a mixture of both solvents. Nanostructures were characterized by XRD to determine the phase obtained and reaction completeness; TEM was used to observe nanostructures morphology, size, size distribution and crystallinity; and finally FT-IR diffuse reflectance was used to study monoethylene glycol presence in the samples. Nanorods in the range of 100–200 nm width were obtained in all samples, but round nanoparticles of around 10 nm in diameter were also detected in samples synthesized only with monoethylene glycol. Samples synthesized in monoethylene glycol were used to fabricate pellets to construct detectors. The detectors responded to ionizing radiation and a resistivity in the order of 1013 Ω cm was estimated. This work proposes, to our knowledge, the first study of BiSI for its application in ionizing radiation detection.

Doped and undoped lead borate glass-ceramics as thermoluminescent detectors

Undoped and Ce and Eu doped glasses and glass ceramic materials with nominal composition 33 % PbO 67 % B2O3 (% in mol), were obtained by melting/quenching technique. Glass ceramics were obtained by subsequent crystallization of glass samples. Glass samples were characterized by Inductively Coupled Plasma (ICP), Differential Thermal Analysis (DTA), Fourier Transform Infrared Spectrometry (FTIR) and UV-Vis spectrometry. Glass-ceramics were characterized by X-Ray Powder Diffraction, and by measuring their therluminescence response as a function of 90Sr irradiation dose. from a lead borate glass intended for thermoluminescence dosimetry, as far as to study the effects that crystallization and Eu and Ce doping produce on their thermoluminescence response. PbB4O7 was found as the only crystalline phase in doped and undoped glass-ceramics. Ce-doping was found to give a narrower bandgap than Eu one, and also introduces new electronical states. Crystallization clearly increases the thermoluminescence response, while undoped material gives higher response up to 20 Gy, although Ce-doping gives linearity up to 35 Gy and a higher response above 20 Gy. Among the studied samples, lead borate glass-ceramics, Ce-doped and undoped, present the best performance and they are then promising materials for thermoluminescence dosimetric applications.