M. C. Caracoche’s research while affiliated with National University of La Plata and other places

... In effect, divalent and trivalent dopants introduce oxygen vacancies into the structure of HfO 2 which in turn, stabilize a high temperature phase of HfO 2 such as the cubic phase [5][6][7]. Some of the well-known dopants to stabilize the cubic phase of HfO 2 include CaO, CeO 2 , MgO and Y 2 O 3 [8]. In fact, the latter three crystallize into the fluorite cubic structure and when used as dopants, compel HfO 2 to stabilize also into its inherent fluorite cubic structure. ...

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Probing the electronic structure of HfO2 polymorphs with Electron Energy Loss Spectroscopy

... Different dopants are generally added to the PSZ solution to stabilize the composite system. Sol-gel method is one of the most adopted methods to develop doped cubic zirconia nanocrystalline powders [5][6][7]. However, the high cost of production makes it commercially unsuitable. ...

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Study on dielectric relaxation and current–voltage characteristics of Mn-doped ZrO2 nanocrystalline solid solution at and above room temperature

... However, there is no report of the thermal decomposition of (NH 4 ) 3 ZrF 7 in air. The thermal behavior of (NH 4 ) 2 ZrF 6 and NH 4 Zr 2 F 9 in air was analyzed but a great difference is observed [22][23][24][25], as listed in Table 1. For example, Yamada et al. [22] and Rodrfguez et al. [23] indicated that NH 4 ZrF 9 lost NH 4 F to form ZrF 4 at 347°C and then converted to ZrO 2 at 400 and 487°C, respectively. ...

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Thermal Decomposition of Ammonium Heptafluorozirconate in Air

... Though the proton-and deuteron-induced reactions are most accessible to the majority of modern cyclotrons, there are alternative routes utilizing helium-4 ions, neutrons, or helium-3 nucleus with comparable cross sections [75][76][77]. Alpha beams afford a particularly attractive reaction route using monoisotopic manganese targets via 55 Mn(α,n) 58m Co. The measured excitation functions are shown below in Figure 12a. ...

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Production, Purification, and Applications of a Potential Theranostic Pair: Cobalt-55 and Cobalt-58m

... Mocoroa studied isomeric ratios for the 133 Cs(d,2n) and 133 Cs(d,p) reactions in the 9.4-28.5 MeV energy range (Mocoroa et al., 1966). Natowitz measured 134m Cs/ 134g Cs isomeric and yield ratios in the 2.5-19.4 ...

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Excitation functions for(d,x)reactions on $^{133}$Cs up to $E_d = 40$ MeV

... Details of the atomic arrangements of materials of technological uses were studied using short range methods as extended X-ray absorption fine structure (EXAFS) [22] and the perturbed angular correlations (PAC) [23,24] techniques. In particular, PAC technique has proved to be an efficient tool in the investigation of the milling effect of the monoclinic zirconia by showing the quadrupole interactions of special atomic arrays through which the monoclinic phase transforms into the tetragonal form [25]. ...

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Phase evolution in the mechanochemical synthesis of stabilized nanocrystalline (ZrO2)0.97(Y2O3)0.03 solid solution by PAC technique

... This observation is contrary to what has been reported for structural-charge-compensating vacancies that are inherent to doped stabilized zirconias. 12,13,18 The DTA/TGA and XRD results can be correlated to some extent with the evolution of the structure of the Zr environments that are revealed in detail by the PAC experiments. This correlation can be performed despite the dissimilar thermal treatments of the experiments that have been conducted in this work (10°C/min in DTA/TGA, at least 2 d at each temperature in in situ PAC measurements and after annealing at increasing temperatures in XRD). ...

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Zirconium Oxide Structure Prepared by the Sol-Gel Route: I, The Role of the Alcoholic Solvent

... It is interesting to note that for HfF 4 ·3H 2 O we observe about 2/3 of a discrete signal and about 1/3 of the anisotropy is lost rapidly [8]. A previous study [13] of this compound did not quote A eff 22 , but the spectra looked like ours and started with about −15% anisotropy which, compared to assumed A eff 22 = −23.0(1)% as in [4], would also give about 2/3 of the total anisotropy for the discrete component. ...

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A Comparative Time Differential Perturbed Angular Correlation Study of the Nuclear Quadrupole Interaction in HfF4·HF·2H2O Using 180mHf and 181Hf(β–)181Ta as Nuclear Probes: Is Ta an Innocent Spy?

... The agreement of orientations of the principal systems and the values of angle from the relation of Casabella et al (1959) and the assumptions involved enable us to state that the first assumption is not so critical, as the molecule of NbCls possesses m and 2/m symmetries. In GaCI a dimer (Peterson and Bridenbaugh 1969; Satyanandam 1974 ) also, the results are in good agreement, although the true symmetry of the molecule is "i. In conclusion, the high value of ~7 and the low value of the NQR frequency in NbCI 5, which are the general characteristics of an ionic compound, and the agreement of the various calculated quantities from the point-charge model, with the experimental frequency and the predicted values of the other NQR parameters are consistent with the ionic nature of NbCI 5. ...

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Electric field gradients in niobium pentachloride dimer

... It is probably the cubic phase stabilized by a small amount of impurities [6]. The characteristic hyperfine parameters for this phase have been reported for different aliovalent impurities and typical values are in the following ranges: ω Q = 90-100 Mrad/s, Á 1 = 0.75-1 and ı 1 = 5-15% [7][8][9]. This phase contains many oxygen vacancies, which produce a nonzero EFG at the probe site. ...

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PAC study of HfO 2 nanofilms grown on Si substrates