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Nuclear energy generation technology is critically linked with the safe disposal of radioactive waste. In this context, iron phosphate glass (IPG) is gaining predominance as nuclear waste vitrification matrix that necessitates a thorough study on the effect of the loading of various nuclear fission waste materials in it. In this study, the effect of the loading of Nd3+ (which acts as a surrogate for radioactive curium (Cm)) and Ru4+ (which is a fission product of 235U) in IPG has been assessed. The optimum loading of Nd3+/Ru4+ leading to the formation of homogenous melt has been ascertained via powder X‐ray diffraction and scanning electron microscopy techniques. The modification in the Fe3+/Fe2+ ratio in IPG and the consequent change in its average coordination number with Nd3+/Ru4+ loading has been deduced from the Mössbauer studies. Local structure analysis has been done using X‐ray absorption spectroscopy at Nd/Ru/Fe K‐edge (as applicable) for all the single and co‐loaded IPG samples. All the co‐loaded samples show enhanced glass stability and glass forming ability compared to unloaded IPG which has been ascertained via detailed thermal studies. The variation in IPG network structure on the addition of Nd2O3 and RuO2 has been ascertained through spectroscopic techniques like Fourier transform infrared (FTIR) and Raman. The base glass and a few representative homogenous single and co‐loaded IPG samples have been irradiated with 4.5 MeV proton beam to simulate the hosting of radioactive elements and the radiation effect on glass structure has been ascertained using FTIR and Raman spectroscopies. The suitability of IPG as nuclear waste vitrification matrix for Nd3+ and Ru4+ is established through all the above analyses. [ABSTRACT FROM AUTHOR]

A near tissue equivalent (Zeff = 10.8) and wide bandgap (Eg = 5.95 eV) Al5BO9: Mn, Li nanophosphor was synthesized by facile gel‐combustion (GC) method, and structural characterizations were performed by XRD, infra‐red, transmission electron microscopy, energy‐dispersive spectra, diffuse reflectance UV–visible spectra, and PL studies. Thermoluminescence (TL) study of Al5BO9: Mn, Li revealed the dosimetry glow peak at 542 K, which was absent in undoped Al5BO9 indicating the importance of Mn dopant. The highest TL response was obtained for the lowest studied dopant concentration (0.1 mol% Mn) that was attributed to the concentration quenching phenomenon. The material is highly reusable with low fading (<10%) up to 110 days. TL response for both thermal neutron and gamma radiations showed excellent linearity within 5 × 109–3 × 1011 n/cm2 and 30–5000 Gy, respectively. These studies suggested promising potential of Al5BO9: Mn, Li nanophosphor in clinical neutron dosimetry and food irradiation dosimetry applications. Based on the variation of calcination temperature, strategy toward dual application, namely, radiation dosimeter and red‐light emitting phosphor of the material was established. For a better understanding of the TL process, various kinetic parameters like activation energy (E), order of kinetics (b), and frequency factor (s) were evaluated using different methodologies, and the results were found to be in good agreement. [ABSTRACT FROM AUTHOR]

The radiation-resistant response of BaTiO3 in the tetragonal and rhombohedral phases on exposure to 100 MeV Ag7+ ion irradiation was investigated by in situ X-ray diffraction (XRD) at room temperature (300 K) and low temperature (25 K), respectively. This study revealed that the BaTiO3 in rhombohedral phase retained crystallinity up to an ion fluence of 1×1014 ions/cm2, whereas tetragonal phase amorphized at much lower fluence viz. 1×1013 ions/cm2. The in situ XRD along with Raman spectroscopy studies revealed that BaTiO3 in rhombohedral phase is more radiation resistant than that of tetragonal phase. The density functional theory ( DFT) calculations confirmed higher bond strength of rhombohedral phase as compared to tetragonal phase, which supported the experimental result of higher radiation stability of rhombohedral phase. The theoretical predictions on high-temperature phase will be of relevance to the nuclear waste applications. [ABSTRACT FROM AUTHOR]

Herein we report the structure, magnetic and dielectric properties of Y2CoMnO6 ( YCMO) and Y2NiMnO6 ( YNMO) prepared under various conditions. On annealing in inert atmosphere, YCMO sample shows a partial decomposition while YNMO remains unaffected. Both YCMO and YNMO samples show paramagnetic to ferromagnetic transition around 80 K, but only the magnetic properties of YCMO samples depend on the preparation conditions. YCMO samples show antiferromagnetic ground state in zero field and a metamagnetic transition at relatively low field (~2 T). Differences in the annealing environment do not destroy the initial antiparallel spin order in YCMO, but affect the critical fields of metamagnetic transition. The field-dependent magnetic properties indicated soft ferromagnetic nature of YNMO samples. The dielectric measurements show distinct frequency and temperature-dependent features in YCMO samples compared to YNMO samples. A large relative permittivity with ε׳ of about 104 is observed in both O2 and air-annealed YCMO samples. Multiple dielectric relaxations are observed in all the annealed YCMO and YNMO samples. [ABSTRACT FROM AUTHOR]

Barium sodium borosilicate glasses containing different amounts of uranium oxides were prepared by conventional melt quench method and investigated for their structural aspects by 29 Si and 11B MAS NMR technique combined with steady-state luminescence and lifetime measurements. Based on MAS NMR studies, it is confirmed that uranium ions act as network modifier up to 15 wt% and beyond which a separate uranium containing phase is formed. From the luminescence studies, it is inferred that uranyl species is in a highly distorted environment. For more than 15 wt% uranium oxide incorporation, weaker U-O-U linkages are formed at the expense stronger U-O-Si/B linkages, as suggested by the excited state lifetime value of the uranyl species as well as red shift in emission peak maximum. For glass samples containing more than 25 wt% uranium oxides, crystalline barium uranium silicate gets phase separated from glass matrix as confirmed by XRD studies. [ABSTRACT FROM AUTHOR]

A series of compositions with general stoichiometry Ca1− x Zr1− x Nd2 x Ti2 O7 has been prepared by high-temperature solid-state reaction of component oxides and characterized by powder X-ray diffraction and electron probe for microanalyses ( EPMA). The phase fields in CaZrTi2 O7- Nd2 Ti2 O7 system and distribution of ions in different phases have been determined. Four different phase fields, namely monoclinic zirconolite, cubic perovskite, cubic pyrochlore, and monoclinic Nd2 Ti2 O7 structure types are observed in this system. The 4M-polytype of zirconolite structure is stabilized by substitution of Nd3+ ion. The addition of Nd3+ ions form a cubic perovskite structure-type phase and thus observed in all the compositions with 0.05 ≤ x ≤ 0.80. Cubic pyrochlore structure-type phase is observed as a coexisting phase in the nominal composition with 0.20 ≤ x ≤ 0.90. Only a subtle amounts of Ca2+ and Zr4+ are incorporated into the perovskite-type Nd2 Ti2 O7 structure. EPMA analyses on different coexisting phases revealed that the pyrochlore and perovskite phases have Nd3+-rich compositions. [ABSTRACT FROM AUTHOR]

In this article, we report the structural phase transitions in Bi4 V2 O11 as observed from temperature-dependent Raman scattering and X-ray diffraction measurements. Four different types of highly disordered coordination polyhedra around the vanadium atoms with large dispersion of V-O bond lengths are observed in Bi4 V2 O11 at ambient temperature. The observed V-O bond lengths could be grouped into two categories, viz. shorter <1.7 Å and longer >1.7 Å. The Raman modes of Bi4 V2 O11 could be assigned to vibration of these bonds and V-O-V linkages. We could correlate the difference in degree of anharmonicity of the phonon modes with temperature to differences in V-O bond strength. The local structure of vanadium-oxygen network in Bi4 V1.8 Cu0.2 O10.7 was also obtained by similar studies. The effect of highly disordered anion sublattice in the doped compound is reflected in the broadening of the Raman modes. [ABSTRACT FROM AUTHOR]

Orthorhombic InVO4 was prepared by solid-state reaction method and characterized by powder X-ray diffraction and scanning electron microscopy. The frequency-dependent dielectric and conductivity properties were studied from 300 to 973 K by impedance spectroscopy. A significantly enhanced conductivity was observed at higher temperature whereas almost no conduction was observed below 723 K. Appreciable grain boundary conductivity was observed at higher temperature. The activation energies for grain and grain boundary conductivities are 0.87 and 1.28 eV, respectively. The relative permittivity of ~35 was observed in a wider range of frequencies and temperatures. The frequency dispersion dielectric studies indicated thermally activated hopping conduction process. The high temperature structural studies revealed no significant change in structural parameters except a gradual increasing trend in the unit cell parameters and amplitude of isotropic thermal parameters with increasing temperature. [ABSTRACT FROM AUTHOR]

Nanocrystalline La1− x Ca x CrO3 ( x = 0.25, 0.40, 0.50) powders were synthesized by gel-combustion process using aspartic acid as a fuel. Phase identification of the samples was carried out by powder X-ray diffraction. Pore distribution and microstructure of sintered pellets were investigated by small angle neutron scattering ( SANS) and scanning electron microscopy ( SEM). SANS and relative density measurement results indicate better sinterability for products with lower Ca2+ concentration. Four-probe direct current electrical conductivity of LaCrO3 with different Ca2+ concentrations was measured in the temperature range 350°C-1000°C in air as well as in hydrogen atmosphere. Linear behavior of Arrhenius plots of electrical conductivities in both air and hydrogen atmosphere indicates charge carrier transport is due to thermally activated hopping conduction of small hole-polarons. It was observed that the electrical conductivity decreased with increasing substitution of Ca2+ concentration instead of increasing small polaron concentration as expected. This trend in electrical conductivity is attributed to the neutralization of some small polarons due to formation of oxygen vacancies with increase in Ca2+ concentration. [ABSTRACT FROM AUTHOR]

The synthesis, characterization, and bulk and lattice thermal expansions of a series of compounds with general composition Cet-xYxO2-x/2 (0.0 ≤ x ≤ 1.0) are reported. The XRD pattern of each product was refined to learn the solid solubility limit and the homogeneity range. The solid solubility limit of YO1.5 in CeO2 lattice, under the conditions of slow cooling from 1400°C, is represented as Ce0.55Y0.45·O1.775 (i.e., 45 mol% of YO1.5). The subsequent compositions were biphase. There was no solubility of CeO2 into the lattice of YO1.5. The bulk thermal expansion measurements from ambient to 1123 K, as investigated using a dilatometer, revealed that the αi (293-1123 K) values, within the homogeneity range, decreased on increased Y3+ content. A similar trend was observed for average lattice thermal expansion coefficient, αn (293-1473 K), as investigated using high-temperature XRD. No ordered phases were obtained in this system under the used conditions. These studies on Ce1-xYxO2-x/2 (0.0 ≤ x ≤ 1.0) system can be used to simulate the phase relation and thermal expansion behavior of Pu1-xYxO2-x/2 (0.0 ≤ x ≤ 1.0), because CeO2 is widely used as a surrogate material for PuO2. [ABSTRACT FROM AUTHOR]

Investigates the formation of nanocrystalline calcia from calcite using transmission electron microscopy. Description of mechanisms facilitating the occurrence of crystallographic transformation; Indexation of diffraction rings; Production of a microstructure of oriented, elongated nanocrystals of calcia.

Orthorhombic InVO4 was prepared by solid-state reaction method and characterized by powder X-ray diffraction and scanning electron microscopy. The frequency-dependent dielectric and conductivity properties were studied from 300 to 973 K by impedance spectroscopy. A significantly enhanced conductivity was observed at higher temperature whereas almost no conduction was observed below 723 K. Appreciable grain boundary conductivity was observed at higher temperature. The activation energies for grain and grain boundary conductivities are 0.87 and 1.28 eV, respectively. The relative permittivity of ~35 was observed in a wider range of frequencies and temperatures. The frequency dispersion dielectric studies indicated thermally activated hopping conduction process. The high temperature structural studies revealed no significant change in structural parameters except a gradual increasing trend in the unit cell parameters and amplitude of isotropic thermal parameters with increasing temperature. [ABSTRACT FROM AUTHOR]