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To address the structural stability of host materials for immobilizing radioactive actinides in nuclear waste management applications, the present study is focused on the effect of various concentrations of Nd substitution on structural properties of synthetic zircon (Nd x Zr 1-x SiO 4-x/2). To achieve this, both pure and Nd-substituted zircon powders were prepared using the solid-state synthesis route. Rietveld refinement of X-ray Diffraction (XRD) data was employed to investigate the impact of various Nd substitutions on the phase composition of the zircon (ZrSiO 4) crystal structure. This refined data was then utilized as input for the analysis of X-ray absorption spectroscopy (XAS) data. The results were further supported by observations from Raman spectroscopy, which indicated the substitution of Zr by Nd. In this work, we present an analysis of both regimes of XAS i.e. X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. Qualitative analysis of XANES data suggests that disorder in the samples increases with higher levels of Nd doping. Additionally, EXAFS analysis around Zr absorption edge also confirms an increased disorder in the system with higher Nd doping levels. However, EXAFS fitting around Nd edge indicated that disorder induced changes are more prominent and Nd–O bond is elongated as compared to Zr–O bond. This disorder in the system escalates at a Nd concentration of 10 atomic % (at %). An important finding of this study is the phase composition analysis using Rietveld refinement of XRD data. While XAS provided an insight into the changes in the local structure, the overall crystal structure remained unaffected even at a high doping of 10 at %. This work provides a comprehensive local structure analysis on this system. Such analysis would help in understanding the structural stability of the system and to determining the maximum loading of actinides in the host zircon for potential nuclear waste management applications. XRD and EXAFS data of representative sample with Nd doping in Nd x Zr 1-x SiO 4-x/2. [Display omitted] • Nd substitution effect on structural properties of Nd x Zr 1-x SiO 4-x/2 was studied. • Samples were synthesized using high temperature solid state synthesis route. • Phase composition of Nd x Zr 1-x SiO 4-x/2 was obtained from Rietveld refinement. • First ever report on local structural analysis by XANES and EXAFS. • These techniques revealed disorder in local structure at higher Nd doping. [ABSTRACT FROM AUTHOR]

5–15 mol % UO 3 loaded zinc iron phosphate glass was prepared by melt quench process. The solubility of UO 3 in ZnIP was determined by XRD and was found to be below 15 mol %; beyond which separation of UP 2 O 7 compound was observed. Mössbauer spectroscopy unraveled the ratio of Fe (II)/Fe(III) and was found to decrease from 0.071 (ZnIP) to 0.029. EXAFS studies unraveled the prevalence of two type of coordination for U–O (i.e U–O 1 and UO 2) and Fe–O (Fe–O 1 and Fe–O 2) in the ZnIP glass matrix, whereas a single chemical environment for Zn–O in the same glass matrix. [ABSTRACT FROM AUTHOR]

Hf (1- x) Y x O 2 (x = 0, 0.10, 0.15, 0.20) epitaxial thin films on YSZ(100) substrate were prepared at different oxygen (O 2) partial pressures (100, 70, 30, and 10 sccm) by pulsed laser deposition. The effect of oxygen partial pressure on crystalline and local structure was investigated using X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) and X-ray absorption spectroscopy (XAS). The surface composition was determined by X-ray photoelectron spectroscopy. The XRD and FTIR studies reveal that undoped HfO 2 thin films remain in monoclinic phase, and the Hf 0.85 Y 0.15 O 2 & Hf 0.80 Y 0.20 O 2 films stabilize in cubic phase at all oxygen pressures, whereas the structure of Hf 0.90 Y 0.10 O 2 films changes from orthorhombic to cubic as oxygen pressure reduces from 100 sccm. The XAS at Hf-L 3 edge and O K-edge shows the changes in bond distances, disorder and hybridization. In monoclinic HfO 2 films the Hf–O bond distance and disorder increases and Hf–Hf bond decreases as the O 2 partial pressure decreases, whereas disorder in doped films shows anomalous behaviour. The oxygen vacancies are evident from both XAS and photoluminescence studies. The results enlighten a deeper understanding of phase change, local structure, optical properties and pave a way to stabilize and identify different technologically important HfO 2 phases for dielectric and ferroelectric applications. • The surface composition of thin films was calculated using XPS technique. • The spectroscopic investigation of phase transformation using FTIR and SXAS technique for Y doped HfO 2 epitaxial thin films deposited at different oxygen partial pressure. • The XRD and FTIR results show that the undoped HfO 2 film is single phase monoclinic at all oxygen partial pressures, whereas Hf 0.90 Y 0.10 O 2 crystal structure is orthorhombic at 100 sccm O 2 partial pressure and cubic at all other pressures. • Hf 0.85 Y 0.15 O 2 & Hf 0.80 Y 0.20 O 2 films remains in cubic phase at all oxygen partial pressures. • The TEM results show epitaxial nature of film, and support the XRD, FTIR and XPS result. • The soft X-ray absorption spectroscopic (SXAS) results confirm the modification in the local electronic structure because of change in crystal structure as well as oxygen partial pressure. • The extended x-ray absorption fine structure (EXAFS) results show that the bond distance and local structure disorder are dependent upon the crystal phase as well as on the oxygen partial pressure. • The photoluminescence areal intensity shows strong dependence on local structure disorder. [ABSTRACT FROM AUTHOR]

In the present work, ionoluminescence (IL) properties of chemically synthesized Mn2+ activated BaMgAl 10 O 17 (BAM) nanophosphors using swift heavy ions (120 MeV Ag9+) is reported under different ion fluence. X-ray diffraction was performed to reveal the structural information of the prepared materials. The oxidation state of the doped Mn ions in BAM was elucidated by X-ray absorption near edge measurements of Mn K-edge and results show that the Mn ions are in divalent state. Initially, the prepared nanophosphors were subjected to photoluminescence (PL) measurement for different doping concentration. Finally, the pellets of the nanophosphors were subjected to IL measurement at room temperature and at a low temperature about 77 K. The PL/IL spectra show a broad band ranging from 470 nm to 610 nm with centered at 521 nm which is attributed to the luminescence centers activated by Mn2+ ions corresponding to 4T 1 →6A 1 transition, responsible for green emission. The PL/IL intensity increases with increase in the doping percentage of Mn ions up to 5% followed by concentration quenching of the luminescence. On the other hand, IL intensity decreases exponentially with increasing ion fluence for all the doping percentage and saturates at higher fluence. It is also observed that the rate of reduction in in the IL is more pronounced at low temperature. • Ionoluminescence (IL) properties of Mn2+ activated BAM nanophosphors are reported. • XANES of Mn K-edge indicates divalent nature of Mn ions. • Green emission due to 4T 1 → 6A 1 transition of Mn2+ ions. • IL intensity decreases with ion fluence. • The rate of reduction in the IL intensity is more pronounced at low temperature. [ABSTRACT FROM AUTHOR]

Abstract We report the structural and optical properties of ternary α-(Ga x Cr (1- x)) 2 O 3 with 0 ≤ x ≤ 0.45 which is synthesized by solid state reaction method. Single phase with space group R-3c is obtained for the gallium composition range of 0 ≤ x ≤ 0.45 and further increase in Ga concentration results in appearance of secondary C 2/ m phase corresponds to Ga 2 O 3. Variations in the in-plane ’ a’ and out of plane ’ c’ lattice parameters shows a clear daviation from the Vegard's law with the bowing parameters of −0.0510 Å and 0.0305 Å respectively. Extended X-ray absorption fine structure (EXAFS) spectroscopy shows larger values of Ga-O bond lengths, which elucidate the deviation in lattice parameters from the Vegard's law and immisibility of Ga in Cr 2 O 3 lattice. Diffuse reflectance spectroscopy (DRS) confirms a blue shift of 0.5 eV in the band gap of α-(Ga x Cr (1- x)) 2 O 3. It has also observed that Cr 3d level shifted towards the O 2p level in the valence band which has been reconfirmed by photo electron spectroscopy. The observed shift indicates enhancement of mixing between these levels which can leads to further delocalization of hole states in the valence band responsible for p-type conduction in the α-Cr 2 O 3. These results suggest that ternary α-(Ga x Cr (1- x)) 2 O 3 (0 ≤ x ≤ 0.45) can be useful in the field of UV transperant electronics and photodetectors. Highlights • Synthesis of α-(Ga x Cr (1- x)) 2 O 3 (0 ≤ x ≤ 0.45) by solid sate reaction method. • Deviation of lattice parameters from the Vegard's law and immiscibility of Ga is discussed. • Tunability of ∼0.5 eV in the bandgap of α-Cr 2 O 3 as a function of Ga composition. • Enhancement in the mixing of Cr d and O 2p states in the valance band. [ABSTRACT FROM AUTHOR]

The structure of WO 3 -TeO 2 glasses containing 15, 20 and 25 mol% WO 3 are studied by neutron diffraction (ND), high energy X-ray diffraction (XRD) and X-ray Absorption Near Edge spectroscopy (XANES). The short-range structural properties of glasses i.e. Te O and W O speciation, coordination number distributions, bond-lengths, and the O Te O, O W O and O O O bond angle distributions in the glass network are determined by the Reverse Monte Carlo (RMC) simulations of the ND and XRD data. RMC technique successfully determined all partial pair correlation functions and the coordination number distributions revealed that glass network consists predominantly of TeO 4 and WO 4 units with small amounts of triangular, penta and hexa co-ordinated units. The average W O and Te O bond lengths are in the ranges: 1.69–1.75 ± 0.01 Å and 1.99–2.00 ± 0.01 Å respectively. Both W O and Te O correlation peaks are asymmetrical, that indicate a distribution of their bond lengths in the respective structural units. The O-Te-O bond angle distribution has a peak at 107 ± 2°. Similarly the O-W-O bond angle distribution has a peak at 108 ± 5°. On increasing the WO 3 concentration from 15 to 25 mol%, the average Te O coordination number decreases from 3.80 to 3.61 ± 0.02 due to the structural transformation: TeO 4  → TeO 3 , similarly the W O coordination also decreases and is in the range: 3.79–3.67 ± 0.02. XANES studies found that the oxidation state of Te and W ions in the glasses are 4 + and 6 + respectively. [ABSTRACT FROM AUTHOR]

Layered oxide material LiNi x Mn y Co z O 2 is emerging out as promising cathode for new generation of Li-ion batteries, especially as power sources for electric vehicles and plug-in hybrid vehicles. In this work, structural and electronic changes occurring in LiNi x Mn y Co z O 2 (LNMC) cathode materials during charge/discharge cycle of the battery is studied over a wide composition range using in-situ X-ray diffraction (XRD) and in-situ X-ray absorption spectroscopy (XAS) techniques. While in-situ XRD measurements decipher the overall structural changes during the charging/discharging cycles, in-situ element specific XAS measurements reveal site specific information on electronic and local structural changes. It has been found that for the LNMC samples the major charge compensation at the metal site during charging or Li ion de-intercalation is achieved by oxidation of Ni2+ ions without significant change in the oxidation state of Co or Mn ions. It is also found that local structure around Ni undergoes reversible change during charging and discharging cycles whereas local structure around Co or Mn sites show no significant change. Moreover, it has been found that local structural changes at Ni sites in the samples with higher Ni concentrations are much less compared to that in the samples with lower Ni concentrations during charging/discharging cycles, the result being corroborated by ab-initio theoretical simulations also. This is a new finding and would have significant implications in determining the optimum composition of LNMC electrodes of Li ion batteries for commercial applications. • LiNi x Mn y Co z O 2 electrodes have been prepared with four compositions with low to high Ni. • Li ion batteries have been prepared using LNMC as cathode material and Li foil as anode. • Operando XAS measurements show major charge compensation happens at Ni sites only. • Operando XAS and XRD show structural changes in samples with higher Ni are much less. • The results have been corroborated by DFT simulations. [ABSTRACT FROM AUTHOR]

The solid-solution formation mechanism and defect dynamics in U 1- x Ce x O 2±δ solid solutions have been investigated by means of X-ray diffraction (XRD) analysis, Raman spectroscopy, and X-ray absorption near-edge structure (XANES) spectroscopy. Diffraction studies have revealed the formation of single-phase solid solutions with a fluorite-type structure at x ≤ 0.2 and a single-phase fluorite-type structure with broadened diffraction peaks, attributed to inhomogeneity in the O/M ratio, at 0.3 ≤ x ≤ 0.8 under reducing conditions. Oxidizing conditions result in the formation of single-phase solid solutions with fluorite-type structure at x ≥ 0.4. Upon the formation of Ce3+ in solid solutions at x ≤ 0.2 under reducing conditions, charge neutrality is achieved through oxygen vacancy creation and formation of higher oxidation states of uranium through a charge compensation mechanism. Lattice parameter–composition relationships for fluorite-type phases synthesized under oxidizing conditions show a decrease in lattice parameters as compared to their stoichiometric counterparts due to the oxidation of U4+ to U5+/U6+. XANES studies provide direct experimental evidence of the presence of Ce3+ in solid solutions, despite synthesis under oxidizing conditions. [Display omitted] • Detailed phase relations reported in U 1−x Ce x O 2±δ system under reducing and oxidizing conditions. • Presence of multivalent cations in F-type solid solutions at x ≤ 0.2 (reduced samples) suggested by lattice parameter trend. • Retention of F-type structure at x ≥ 0.4 in oxidizing conditions despite presence of combination of oxidation states. • Defect dynamics and solid solution formation mechanism elucidated by conjunction of XRD, Raman spectroscopy and XANES. • Presence of Ce3+confirmed by XANES in air-synthesized U 1-x Ce x O 2+δ. [ABSTRACT FROM AUTHOR]

We present a detailed study on post synthesis annealing effects on luminescence as well as electronic and structural properties of pure and Terbium doped (5 wt%) CePO 4 nanowires (NWs) prepared using green synthesis chemical route. The formation of nanowire was confirmed from transmission electron microscopy and small angle X-ray scattering measurements, revealing elongated nanowire shape with monoclinic crystal structure in agreement with X-ray diffraction observations. Photoelectron spectroscopy data analysis showed that samples annealed under air consist of only Ce4+ oxidation state, while those annealed under N 2 environment showed the presence of mixed Ce4+ and Ce3+ oxidation states. However, this Ce4+ oxidation state has not propagated inside the bulk of NWs as seen from X-ray absorption spectra around Ce L III absorption edge. The photoluminescence measurements revealed significant differences between the samples annealed in air and N 2 flow respectively. Post synthesis annealing under N 2 flow helped to suppress the contribution of Ce4+ oxidation state in photoluminescence. The overall results are beneficial from the luminescent device point of view and form a basis for advance studies. • Pure and Tb:CePO 4 nanowires were prepared using green synthesis chemical route. • Elongated nanowires (diameter: ∼5–10 nm, length ∼60–100 nm) were observed. • PES showed a dominating presence of Ce4+ oxidation state on the surface. • Interior (bulk) of the samples consist only Ce3+ oxidation state as seen from XAS. • PL intensity enhanced when surface Ce4+ contribution was suppressed by N 2 annealing. [ABSTRACT FROM AUTHOR]

Pure, Co doped and (Co, Cu) co-doped ZnO nanocrystals have been prepared by wet chemical route at room temperature to investigate the effect of Cu doping in Co doped ZnO nanocrystals . The nanocrystals have initially been characterized by X-ray diffraction, FTIR, Raman, optical absorption and EPR spectroscopy and the results were corroborated with DFT based electronic structure calculations. Magnetic properties of the samples have been investigated by studying their magnetic hysteresis behavior and temperature dependence of susceptibilities. Finally the local structure at the host and dopant sites of the nanocrystals have been investigated by Zn, Co and Cu K edges EXAFS measurements with synchrotron radiation to explain their experimentally observed magnetic properties. [ABSTRACT FROM AUTHOR]

In this study, effect of Nd doping, as a dopant material on the structural, optical and electronic properties of lanthanum monazite structure has been studied. Pure and Nd:LaPO 4 powders with varying Nd concentrations were prepared via conventional high-temperature solid-state reaction method. Compositional information obtained using Energy dispersive X-ray spectroscopy showed that within the detection limit, no impurities were present in the samples. Oxidation states of the elements were confirmed from X-ray photoelectron spectroscopy (La and Nd) and X-ray absorption near edge structure studies (La). X-ray diffraction showed the formation of monoclinic crystal structure without any phase impurity. Fourier transform infra-red spectroscopic measurements confirmed the substitution of Nd in LaPO 4 matrix. We also report the first ever local structure analysis using Extended X-ray absorption fine structure which showed that the Nd atoms have successfully substituted La atoms in LaPO 4 matrix. The bandgaps were obtained from Diffuse reflectance UV-Visible spectroscopy. [Display omitted] • Nd doping effect on structural, optical, electronic property of LaPO 4 was studied. • XRD showed pure monoclinic crystal structure without any phase impurity. • First ever report on local structure by EXAFS showed La substitution by Nd atoms. • Oxidation states of elements were confirmed from XPS and XANES. • FTIR revealed presence of PO 4 tetrahedra without any other chemical impurity. [ABSTRACT FROM AUTHOR]

Undoped and various rare earth ion doped SrZrO 3 (SZO) perovskite based phosphors have been synthesized using the gel-combustion technique employing citric acid as a fuel. The phase purity of the sample is confirmed by the X-ray diffraction (XRD) technique. It was observed that average particle size of perovskite particle was around 100 nm. In order to probe the local structure and symmetry around lanthanide ions in SrZrO 3 , detailed experimental investigation has been carried out. X-ray absorption near edge fine (XANES) measurements along with their respective emission spectroscopy confirm that on doping lanthanide ion; in cases they were found to get stabilized as trivalent species. Extensive time resolved emission spectroscopy (TRES) on doped samples shows that on doping Sm 3+ in SZO; an efficient energy transfer takes place and Sm 3+ ions are localized both in Sr and Zr positions of SZO. PL decay time shows the presence of two life time values in case of nanocrystalline SrZrO 3 :Sm 3+ : (i) Sm 3+ at Zr 4+ site ( τ =500 µs) and (ii) Sm 3+ at Sr 2+ site ( τ =1.2 ms) in the ratio of 3:1. Based on TRES for europium doped sample, it was inferred that, two different types of Eu 3+ ions were present in the SZO matrix. The first type was a long lived species present at relatively higher symmetric site of 'Sr 2+ ' and the second was a short lived species present at relatively lower symmetric 'Zr 4+ ' site which gets selectively excited at 296 nm. Dysprosium ion specifically occupies Zr 4+ site only in SZO. EXAFS studies supported the TRES results. [ABSTRACT FROM AUTHOR]

The modified sodium borosilicate glass was synthesized by incorporating CaO, TiO 2 and Al 2 O 3 to the primary glass forming constituents (SiO 2 , B 2 O 3 and Na 2 O) and on melting the mixture at 1373–1473K/3h by melt quench method. Uranium loaded analogues were synthesized by adding varying amounts of UO 3 (2,4,6 and 8 mol %) to the borosilicate glass forming reagents then on melting at 1373–1473K. The U-loaded matrices were characterized by XRD to ensure the formation of glass matrices. Solubility of uranium in sodium borosilicate glass has been investigated. Further, the glasses were characterized by X-ray photoelectron spectroscopy (XPS) to unravel the oxidation states of uranium in the modified glass composition. X-ray absorption spectroscopy (EXAFS) revealed the chemical environment of uranium in the glass matrix indicating the coordination number of U in glass. Image 1 • Modified borosilicate glass 47SiO 2 -24B 2 O 3 -17Na 2 O-9.5CaO-1.0Al 2 O 3 -1.5 TiO 2 was prepared. • 2–8 mol% of UO 3 in the form of U 3 O 8 was loaded to the modified borosilicate glass. • Above 6 mol% of UO 3 loading, Na 2 U 2 O 7 separated out from the glass unravelled by XRD studies. • XPS studies show the presence of U in two different oxidation states (U6+ and U4+). • EXAFS studies reveal a decrease in coordination of uranium in glass matrix on increasing uranium loading. [ABSTRACT FROM AUTHOR]