J. Azorín

Preparation of CaSO4:Dy by precipitation method to gamma radiation dosimetry

This paper presents the results of the preparation and characterization of dysprosium-doped calcium sulfate (CaSO(4):Dy) phosphor, which was obtained by homogeneous precipitation from calcium acetate Ca(CH(3)COO(-))(2). Structural and morphological characteristics were studied using a scanning electronic microscope (SEM). The structure of all compounds was determined by X-ray diffraction method too. Thermoluminescence (TL) emission properties of CaSO(4):Dy under gamma radiation effects were studied. This phosphor powder presented a TL glow curve with two peaks (Tmax) centered at around of 180 and 300 degrees C, respectively. The TL response of CaSO(4):Dy as a function of gamma absorbed dose was linear in a wide range. Both emission and excitation spectra were also obtained. Results showed that this new preparation method of CaSO(4):Dy TL phosphor is less expensive, cleaner and safer than the conventional preparation method.

Thermoluminescence (TL) of europium-doped ZrO2 obtained by sol–gel method

This article reports the preparation and characterization of europium-doped zirconium oxide (ZrO2:Eu3+) formed by homogeneous precipitation from propoxyde of zirconium [Zr(OC3H7)4]. The alkoxide sol gel process is an efficient method to prepare the zirconium oxide matrix by the hydrolysis of alkoxide precursors followed by condensation to yield a polymeric oxo-bridged ZrO2 network. All compounds were characterized by thermal analysis and the X-ray diffractometry method. The thermoluminescence (TL) emission properties of ZrO2:Eu3+ under beta radiation effects are studied. The europium-doped sintered zirconia powder presents a TL glow curve with two peaks (Tmax) centered at around 204 and around 292 °C, respectively. TL response of ZrO2:Eu3+ as a function of beta-absorbed dose was linear from 2 Gy up to 90 Gy. The europium ion (Eu3+)-doped ZrO2 was found to be more sensitive to beta radiation than undoped ZrO2 obtained by the same method and presented a little fading of the TL signal compared with undoped zirconium oxide.

Effect of thermal treatment on TL response of CaSO4:Dy obtained using a new preparation method

We report the effect of thermal treatment on thermoluminescent (TL) sensitivity property of CaSO4:Dy obtained by a new preparation method at Instituto Nacional de Investigaciones Nucleares (ININ) of Mexico. Samples of phosphor powder were subjected to different thermal treatments respectively at 773, 873, 973 and 1,173K for 1h and then irradiated from 0.1 to 1,000 Gy gamma doses. Low energy dependence was analyzed too by irradiating with X-rays in the range of 16-145 keV. The results were normalized to the energy (1,252 keV) of (60)Co and they were compared with those obtained using the commercial dosimeters TLD-100. Also the kinetic parameters were determined by deconvolution of glow curve.

Preparation of luminescent nanocrystals started from amorphous zirconia prepared by sol–gel technique

This article reports the experimental results concerning the thermoluminescent (TL) and photoluminescent (PL) characteristics of nanopolicrystalline zirconium oxide (ZrO2) powder prepared by the conventional sol–gel method. Transmission electron miscroscopy and X-ray diffraction techniques were used for morphological and structural characterization of the compound. Thermal annealing processes for the precipitates were studied. It is observed that the crystalline structure and the crystallinity of the powders depend on the annealing temperature. For temperatures higher than 1000 °C, the material presents the monoclinic phase with an average crystalline grain size of 40 nm. The TL glow curve of the undoped ZrO2 has a simple structure with two prominent peaks at around 160 and 270 °C, with a small shoulder in the second peak. TL response of the ZrO2 as a function of beta-irradiation showed a wide range of the dose. Fading and reusability of phosphor were also studied. Measurements on PL show excitation and emission spectra.

Structural characteristics of nanocrystalline ZrO2 powder sol–gel derived to luminescent applications

Interest in nanocrystalline ceramics is increasing nowadays. Sol–gel is a low temperature method, which uses chemical precursors to produce ceramics and glasses with better purity and homogeneity than the conventional high-temperature processes. This new preparation method of nanophosphors has been recently strongly developed for producing high-efficiency luminescent devices. When producing ZrO2 it is important to retain a high degree of crystallization of ZrO2 and its possible correlation with the concentration of defects. The X-ray diffraction patterns of ZrO2 showed that the calcined material has a strongly monoclinic structure. The thermoluminescent glow curve of ZrO2 exhibited two peaks. Photoluminescence spectra of ZrO2 also were obtained.

An alanine-boron compound for thermal neutron fluence measurements. Part 1 synthesis and development

Abstract An alanine-boron compound was synthesized and chemically characterized to be used for thermal neutrons fluence measurements. The synthesis of the compound was made by reacting the amino acid alanine with boric acid in three different media: acidic, neutral and alkaline. Chemical analysis showed that the alkaline medium is favorable for the synthesis. This paper includes preliminary results of the use of the alanine-boron compound as a thermal neutron fluence detector. The technique used is the detection of the free radical yield upon thermal neutron irradiation by electron paramagnetic resonance (EPR).

Thermoluminescent response of CaSO4:Dy+PTFE induced by X-ray beams

The aim of the present work was to evaluate the feasibility of the utilization of CaSO4:Dy pellets for X-ray measurements in a general radiology department. Thermoluminescence (TL) response of CaSO4:Dy+PTFE was compared to the TL response of commercial LiF:Mg,Ti (TLD-100) samples. TL pellets were exposed to X-ray beam from X-ray machine CMR for clinical diagnosis purpose. The calibration curve of CaSO4:Dy+PTFE was obtained and it showed a linear response as a function of absorbed dose in air at the studied dose interval. Despite this fact, this material can be used for X-ray beams measurements if appropriate calibration procedures are performed.

Nanostructural processing of advanced thermoluminescent materials

The growing interest in transition ceramic nanoparticles doped with various elements is in constant increasing due to their size-dependent physical properties and its potential applications in thermo-luminescence dosimetry. Zirconium oxide (ZrO2) is a very important semiconductor material having a wide band gap with different interesting applications. Undoped zirconium oxide (ZrO2) and zirconium oxide doped with various elements (ZrO2:VD) have been prepared by thermal treatment of precursor sol–gel glasses. The dependence on annealing temperature and time has been analyzed. The structural analysis of the samples has been made by X-ray diffraction (XRD). The nanocrystals obtained had grain sizes ranging from 8 to 40 nm. Thermally Stimulated Luminescent glow curves were obtained and analyzed.

AN ALANINE-BORON COMPOUND FOR THERMAL NEUTRON FLUENCE MEASUREMENTS. PART 2: EPR RESPONSE

Abstract In a previous paper the synthesis in three different media (acidic, neutral and alkaline) of an alanine–boron compound to be used for thermal neutron fluence measurements was reported. The present work studies the electron paramagnetic resonance (EPR) signal response of the three preparations to thermal neutron irradiation (φ=5×107 n/cm2s). The following EPR signal parameters of the samples were investigated: peak-to-peak signal intensity vs. thermal neutron fluence Φ=φΔt; where Δt=1, 5, 10, 20, 40, 60, 80, 90, 100, 110 and 120 h, peak-to-peak signal intensity vs. microwave power, signal fading, repeatability, batch homogeneity and zero dose response. It is concluded that these new products could be used in thermal neutron fluence estimations.

Thermoluminescent characteristics of synthetic hydroxyapatite (SHAp).

This paper presents the experimental results of the thermoluminescent (TL) characteristics of synthetic hydroxyapatite (SHAp) obtained by the sol-gel method. For preparation of the SHAp powders, phosphorus pentoxide (P2O5) and calcium nitrate tetrahydrated (Ca(NO3)2-4H2O) were used. The powders obtained were submitted at different temperatures. The structural and morphological characterization were carried out using X-ray diffraction (XRD) and scanning electron microscopy techniques. TL glow curve exhibited two peaks centered at around 200 °C and 300 °C. TL response of SHAp as a function of gamma absorbed dose was linear over a wide dose range. Fading of the storage information in the samples irradiated was also studied. The experimental results show that the synthetic hydroxyapatite obtained by the sol-gel method may have used in gamma radiation dosimetry applications.