Chemically flexible A2B2O7 oxides are attractive candidates for designing structure-specific functional materials by judicious substitution. However, modulating functionality by substitution is governed by the solubility limits of the substituent. Present work reports an a typical 10 mol % solubility of Y3+ in La2Ti2O7(LTO:10Y), substantially lower than 60 mol %, anticipated by cationic radius ratio guidelines (rA/rB) for A2B2O7. Systematic experimental and theoretical investigations have been performed to justify this limited solubility. The solubility of Y3+ in La2Ti2O7 was verified by XRD at the bulk scale and via an Eu probe at the polyhedral level. Whereas XRD shows phase segregation beyond 10 mol % Y3+, the 0.5 mol % Eu3+-codoped LTO:10Y sample showed typical Eu3+ emissions, advocating structural homogeneity. However, the corresponding excitation spectrum revealed that insertion of Y3+ in LTO enhanced the energy transfer by the titanium-oxygen polyhedral network, [TiO6]8- → Eu3+. These observations were rationalized through density functional theory (DFT) calculations, which unveiled yttrium's preference for a low-coordination La site that substantially modifies adjacent TiO6 polyhedra and influences the energy transfer. Combined experimental and theoretical studies propose that yttrium's preference for a lower coordination number and a shorter/stronger metal-oxygen bond renders site selectivity and simultaneous regulation of the TiO6 network, limiting its solubility in La2Ti2O7. Thus, it provides supporting evidence for bonding-controlled substitution of yttrium in La2Ti2O7, rendering solubility lesser than that endorsed by radius ratio guidelines.

The thermophysical properties of the yttria stabilized zirconia - magnesium oxide (YSZ-MgO) ceramic composite system are investigated to comprehend its potential for high-temperature applications. Single-component YSZ, single-component MgO and YSZ-MgO composite pellets with varying weight ratios (75:25, 50:50 and 25:75 wt%) were synthesized. SEM images revealed the formation of well-defined particles, with YSZ showing a single composition, while YSZ-MgO displayed a composite structure with distinguishable YSZ and MgO grains. HT-XRD confirmed that both YSZ and MgO exist in cubic phase in a wide temperature range of room temperature to 1000 degrees C. Additionally, all the YSZ-MgO composites remained biphasic throughout, indicating retention of immiscibility over the temperature range studied and demonstrating their high phase stability. The lattice thermal expansion behaviour of YSZ remained nearly identical across compositions, viz. in the range of similar to 10.6 x 10-6 K-1, suggesting that the composite formation does not significantly affect the inherent thermal expansion properties of YSZ. On the other hand, the lattice thermal expansion coefficient of MgO is found to be similar to 5% lesser in the composites. Concurrently, the bulk linear thermal expansion varied with composition with the value increasing with increasing MgO content. Specifically, compared to single-component YSZ, the bulk linear thermal expansion coefficient for the YSZ-MgO composites exhibited an increase by similar to 13%-27%. The YSZ-MgO composites exhibited an increased thermal conductivity of 2.8 Wm-1K-1 and 4.7 Wm-1K-1, at room temperature, for 25 and 50 wt% MgO respectively compared to 1.2 Wm-1K-1 for single-component YSZ. These findings highlight the thermal stability of YSZ-MgO composites, thus indicating their potential application in high-temperature environments, including nuclear reactors.

The study reports structural and electrical evolution in La3+/Mn3+ cosubstituted BaTiO3, with compositions LaxBa1-xMnxTi1-xO3 (x = 0.00-0.50) in search of lead-free energy storage materials. Solid-state synthesized samples were thoroughly characterized by XRD, Raman spectroscopy, XPS, SEM, AC-impedance, and P-E measurements. Structural analysis revealed a tetragonal-to-rhombohedral (T to R) phase transition with increasing substitution, accompanied by lattice distortion and reduced tetragonality. Raman spectroscopy could clearly delineate R-type modes in otherwise single-phasic (T) La0.05Ba0.95Mn0.05Ti0.95O3. XPS confirmed mixed valence states of Mn (Mn2+/Mn3+) and O-vacancies which influenced structural and electrical behavior. Introduction of 2 mol % La3+/Mn3+ led to doubling of dielectric permittivity, K (∼1205), relative to BaTiO3. This is attributed to plausible distortion in BaO8/TiO6 polyhedra caused by occupancy of the same lattice sites by ions of varying sizes and oxidation states. The composition La0.05Ba0.95Mn0.05Ti0.95O3 showed an almost frequency-independent K (∼400) and low dielectric loss (0.05). LaxBa1-xMnxTi1-xO3 (x ≥ 0.1) yielded lossy, conduction-dominated behavior consistent with defect-facilitated ion transport. Simultaneous occurrence of ferroelectricity and visible band gap (2.23 eV) in La0.02Ba0.98Mn0.02Ti0.98O3 proposes a potential ferroelectric-photovoltaic material. These results establish La/Mn codoping in BaTiO3 as an effective strategy to yield ferroelectrics, low-loss dielectrics, and conductors by composition-driven structural tailoring.

The current work involves the preparation, characterization, and application of zirconia-doped bimetallic oxide (CeZrO4-delta) as an efficient catalyst for the transesterification of ethylene carbonate (EC). In this study, we report fluorite CeZrO4-delta as a highly active, durable, and reusable catalyst for converting EC to dimethyl carbonate. The catalysts were prepared using a gel combustion method, followed by calcination, and then subjected to catalytic activity tests. The prepared catalyst was thoroughly characterized using various physicochemical techniques. Additionally, the catalyst can be recycled and reused up to six runs with minimal loss of reactivity. Both fresh and recycled catalysts were analyzed using several methods, including X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, Raman analysis, ICP-OES, and Brunauer-Emmett-Teller (BET) analysis. The use of earth-abundant, recyclable mixed-metal oxide catalysts highlights the environmentally benign nature of this approach.

ABSTRACT Rare earth niobates (RENbO 4 ) are structurally fascinating utilitarian compounds for high temperature applications. The pursuit of understanding the implications of RE 3+ ‐ionic size on its wide‐ranging properties motivated the synthesis and investigation of RENbO 4 (RE: La, Nd, Sm, Gd, Dy, and Y) by diffraction, spectroscopic, luminescence, and thermomechanical studies. Single‐phasic fergusonite ( I 2/ c ) structure with lattice parameters proportional to RE 3+ ‐radius, transform to tetragonal scheelite ( I 4 1 / a ) at transition temperatures ( T c ), inversely proportional to RE 3+ ‐size. Various crystal chemistry parameters such as monoclinic distortions, landau order parameters (𝜂) and spontaneous strain ( ε s ) decreased with temperature as the symmetrical scheelite structure is approached, but strain parameters behave rather differently. Longitudinal strain decreases but shear strain increases with RE 3+ ‐size, and hence the ε s exhibits a maximum. The lattice thermal expansion coefficients (LTE) showed anisotropic behavior along different crystallographic axes and decrease with decrease in RE 3+ ‐size. Continuity in Δl/l versus T , but a change in slope at T c in thermomechanical studies, indicates the second‐order nature of fergusonite–scheelite phase transition, which is also supported by variation of ε s versus 𝜂. Bulk thermal expansion coefficients for monoclinic structures exhibited a decrease from La to Y (14.5 ppm to 10.1 ppm), but a slight increase (9.6 ppm to 10.4 ppm) for the tetragonal. The knowledge of dependence of critical functionalities of RENbO 4 on RE‐size provides a key to design functionality‐specific compounds.

Chemically flexible A2B2O7 oxides are attractive candidates for designing structure-specific functional materials by judicious substitution. However, modulating functionality by substitution is governed by the solubility limits of the substituent. Present work reports an a typical 10 mol % solubility of Y3+ in La2Ti2O7(LTO:10Y), substantially lower than 60 mol %, anticipated by cationic radius ratio guidelines (r A/r B) for A2B2O7. Systematic experimental and theoretical investigations have been performed to justify this limited solubility. The solubility of Y3+ in La2Ti2O7 was verified by XRD at the bulk scale and via an Eu probe at the polyhedral level. Whereas XRD shows phase segregation beyond 10 mol % Y3+, the 0.5 mol % Eu3+-codoped LTO:10Y sample showed typical Eu3+ emissions, advocating structural homogeneity. However, the corresponding excitation spectrum revealed that insertion of Y3+ in LTO enhanced the energy transfer by the titanium-oxygen polyhedral network, [TiO6]8- -> Eu3+. These observations were rationalized through density functional theory (DFT) calculations, which unveiled yttrium's preference for a low-coordination La site that substantially modifies adjacent TiO6 polyhedra and influences the energy transfer. Combined experimental and theoretical studies propose that yttrium's preference for a lower coordination number and a shorter/stronger metal-oxygen bond renders site selectivity and simultaneous regulation of the TiO6 network, limiting its solubility in La2Ti2O7. Thus, it provides supporting evidence for bonding-controlled substitution of yttrium in La2Ti2O7, rendering solubility lesser than that endorsed by radius ratio guidelines.

Lithium lanthanum titanium oxide (LLTO) is a promising solid electrolyte (SE) for solid-state batteries, owing to its excellent chemical and thermal stability, wide electrochemical window, and high ionic conductivity even at room temperature. However, the influence of lattice dynamics and local structural features on lithium transport remains poorly understood. In this study, we employ large-scale machine-learned molecular dynamics (MLMD) simulations alongside inelastic neutron scattering (INS) measurements to reveal the role of strongly anharmonic soft phonons in Li-ion diffusion. Unlike many other materials where soft phonons facilitate ion transport, we find that in LLTO, these phonons suppress Li diffusion by inducing tilt or rotational distortions in the lattice. These distortions constrict the bottlenecks that significantly hinder ionic conductivity. Our results show that stabilising these soft phonon modes and thereby restricting the oxygen dynamics, combined with the inherent anharmonicity of Li-related vibrations, can substantially enhance Li diffusion. Thus, in perovskite-based SEs, soft phonon modes and oxygen dynamics emerge as critical descriptors for designing advanced electrolytes. Additionally, our investigation of lattice thermal conductivity using the Green-Kubo formalism reveals glass-like thermal transport behaviour, arising from the disordered structure and extremely anharmonic soft modes.

This study investigates the radiation tolerance of yttria-stabilized zirconia (YSZ)-magnesium oxide (MgO) ceramic composites with varying MgO concentrations (0-50 wt%), subjected to 400 keV Kr2+ ion irradiation at ambient temperature. The focus is on understanding the response of composites vis-a`-vis single-component material viz. YSZ in the ballistic collision regime. Scanning electron microscopy (SEM) revealed an increase in the surface roughness along with the formation of gaps between YSZ-MgO and/or MgO-MgO grains after irradiation, likely due to grain shrinkage. X-ray diffraction (XRD) and Raman spectroscopy measurements demonstrated that YSZ-MgO composites exhibit superior radiation tolerance compared to YSZ alone with a noticeable reduction in the radiation induced microstructural damage with increasing MgO concentration. A noticeable increase in strain was estimated upon irradiation in single-component YSZ, while the strain was comparatively lower in YSZ-MgO (75-25 wt%) and negligible in YSZ-MgO (50-50 wt%). X-ray absorption near edge structure (XANES) measurements did not indicate any change in the oxidation state of Zr ions post-irradiation in any of the samples. Extended X-ray absorption fine structure (EXAFS) analysis revealed that changes in co-ordination number, bond length and local atomic disorder after irradiation were significantly lower in the composite samples compared to YSZ. This enhanced radiation tolerance of the composites is attributed to the presence of heterointerfaces in the composites, which act as more efficient defect sinks than grain boundaries in homogenous YSZ. Consequently, defects generated during irradiation are more effectively annihilated in the composites. Furthermore, the quantity of heterointerfaces increases with increasing MgO concentration, leading to greater radiation resistance in the composites with higher MgO concentrations.

Rare-earth perovskites possess structural features conducive to co-existence of interesting functionalities. This study establishes structural tunability of B-site tailored GdFeO3 and its implications. Isovalent introduction of In3+ at B-site by hybrid synthesis approach yielded GdInxFe1-xO3 (0.0 <= x <= 1.0) system. The synthesis-route adopted could enable stabilization of metastable C-type and hexagonal (H) polymorphs that eventually led to thermodynamically stable phases in H (hexagonal), O (orthorhombic) and biphasic (H + O) phases. Gradual evolution of phases with respect to temperature as well as composition were studied with XRD, HT-XRD and Raman spectroscopy. Density functional theory was employed to explain prevalence of wide biphasic-field and it was attributed to non-favourable energetics of Fe3+ at trigonal-bipyramidal site in H-polymorph. The system exhibits structure and composition-dependent electrical behaviour and tunable band gap. Detailed study highlighted a very low leakage current(I) and low dielectric loss in In3+-rich polymorphs(H). Typically, GdInO3 shows I of 4 x 10(-9) A/cm (2) , high dielectric constant (epsilon) of 106 with a stable loss of 0.009. The energy storage performance showed decrease in recoverable E-density (W-rec) and increase in energy storage efficiency with In3+-content. Optimum properties were observed for equimolar composition, GdIn0.5Fe0.5O3 (W-rec= 560 mJ/cm(3); eta = 82 %). An intriguing observation is effect of structure on visible light-catalysed degradation of methylene blue with Opolymorphs showing excellent photodegradation ( 99 % dye/180 min) while H-polymorphs performing abysmally. This is explained based on band gaps, surface charges and plausible difference in generation of photo- induced charge carriers.

Polycrystalline samples of nominal composition BiFe0.5Co0.5O3 were prepared by solid state reaction, nitrate decomposition as well as gel-combustion procedures, and characterized by powder XRD studies. The XRD studies indicated formation of sillenite type cubic (I23) phase in all the cases while having few additional weak peaks accountable to spinel type phase. It was observed that the sample prepared by gel-combustion show better crystallinity and phase purity compared to other methods. Powder neutron diffraction studies carried out at ambient and 7 K on the sample prepared by gel-combustion indicated that the studied sample has coexisting Fe3O4 and Co3O4 along with the sillenite type phase with composition Bi25FeO40. Additionally, the ferromagnetism observed in the sample is attributed to the ferrimagnetic spinel phase. Further the lattice contraction on lowering temperature or increasing pressure was concluded from the low temperature neutron diffraction studies and in situ high pressure XRD studies in DAC using synchrotron radiation source. The lattice shows only minor (similar to 1 %) decrease in unit cell volume while cooling from ambient to 7 K, whereas it shows an appreciable contraction (similar to 16 %) on increasing the pressure up to 21.5 GPa. The coefficient of average volume thermal expansion in the temperature range of RT to 973 K is found to be 47.1 x 10(-6) K-1. Also, the sillenite phase shows stability up to 21 GPa, the maximum pressure of this study and does not show any pressure induced amorphization as commonly observed in Bi2O3 and its other related compounds. The analyses of the pressure evolution of unit cell parameters by using a 3rd order Birch-Murnaghan EOS indicated the bulk modulus (B-0) of 55(4) GPa and its pressure derivative (B0 ') 8.4(7), and linear modulus (M-0) 122(18) GPa and its pressure derivative (M0 ') 47(9). The observed low value of bulk modulus is in accordance with its loosely packed structure with active lone pair on Bi3+.

High entropy oxides provide an exciting avenue to obtain superior functionalities. However, stabilizing high entropy oxides containing equimolar components is a challenge in structures that are highly sensitive to the size of constituting ions. Hexagonal ABO3 (P63cm) is one such structural class that shows improper ferroelectricity due to non-centrosymmetric placement of ions. The motivation for this work was to stabilize a high entropy YInO3-based hexagonal composition, which has not been reported earlier, and its impact on electrical properties. Tailoring synthesis conditions yielded single-phasic hexagonal polymorphs for YInO3, Y(In0.5Mn0.5)O3, Y(In0.33Mn0.33Fe0.33)O3, and Y(In0.25Mn0.25Fe0.25Ga0.25)O3. Sharp XRD peaks with very broad Raman modes and decrease in the grain size support a single hexagonal phase with strong randomization. Entropy stabilization was established by positive enthalpy of formation determined by Calvet-calorimetry. These hexagonal polymorphs have differential thermal expansions, with a/b-axes showing double expansion compared to c-axis, which is attributed to unbuckling of BO5 layers that provides a buffer in the c-direction. Interestingly, as the B-site randomizes, BO5 polyhedra become more regular, accompanied by an increase in the B-Oplanar-B angle, which increases local symmetry and tends to reduce inherent polarization. Y(In0.25Mn0.25Fe0.25Ga0.25)O3 exhibits a low dielectric loss of ∼0.0085 and an ultra-low leakage current of 5.2 × 10-10A/cm2 (upto 150 °C), an order of magnitude improvement over YInO3.

Silicate frameworks exhibit diverse structural responses under extreme conditions, which are strongly influenced by hydration. Here, we present a comparative high-pressure synchrotron X-ray diffraction study of Na2ZrSi2O7 and its hydrated analogue Na2ZrSi2O7·H2O up to 30 GPa, combined with electronic structure calculations. At ambient conditions, both phases share the same primary building units (PBUs: [ZrO6] and [SiO4]) but differ in secondary building units (SBUs, M2T4 vs M2T6). Under compression, Na2ZrSi2O7 undergoes a phase transition near 15 GPa, while the hydrated phase remains stable throughout the pressure range. The anhydrous compound exhibits a higher bulk modulus (B0 = 77.1 GPa) and less anisotropic compression compared with those of the hydrated phase (B0 = 66.3 GPa). Distinct deformation mechanisms are observed: the anhydrous framework accommodates pressure through [ZrO6] octahedral distortion, whereas the hydrated framework compresses via [Si2O7] group tilting. Electronic structure calculations indicate band gap widening with pressure in both phases; notably, Na2ZrSi2O7 shows a direct-to-indirect band gap transition, whereas the hydrated phase retains a direct gap. These results reveal how hydration-driven topological modifications at the SBU scale dictate the pressure-induced structural evolution, phase stability, and electronic properties of zirconosilicate frameworks.

In response of swift heavy ion (100 MeV I9+) irradiation, the irradiation-induced disordering in nonstoichiometric pyrochlore composition (Nd1.8Zr2.2O7.1) was compared to that of stoichiometric composition Nd2Zr2O7. Both compositions were prepared through auto gel-combustion followed by sintering under the identical conditions. Systematic analysis of the compositions before and after irradiation was performed with X-ray diffraction (XRD), Raman spectroscopy, and plane-view high-resolution transmission electron microscopy (HRTEM) techniques. Irradiation caused pyrochlore to amorphous phase transformation was observed in both compositions except the slower rate of amorphization in Nd1.8Zr2.2O7.1. The amorphization was achieved as a consequence of isolated disordered track overlapping at higher ion fluence with the estimated track diameter 2.73 +/- 0.05 and 3.46 +/- 0.30 nm for Nd1.8Zr2.2O7.1 and Nd2Zr2O7, respectively, employing the framework of single-ion impact model to XRD results. HRTEM micrographs also revealed the less prevalence of irradiation-induced amorphization in Nd1.8Zr2.2O7.1 with the observed irradiation-induced modified track region composed of defect-rich pyrochlore structure, anion-deficient fluorite structure, and amorphous domains; with the diameter of 3.0 +/- 1.0 nm and 5.0 +/- 1.0 nm in Nd1.8Zr2.2O7.1 and Nd2Zr2O7, respectively. The preexisting anion-deficient fluorite structure in Nd1.8Zr2.2O7.1 helps in its epitaxial growth as recovered structure from melted ion track during irradiation-induced rapid cooling.

We present the investigations on atomic dynamics and Li+ diffusion in crystalline and amorphous Li2Si2O5 using quasielastic (QENS) and inelastic neutron scattering (INS) studies supplemented by ab-initio molecular dynamics simulations (AIMD). The QENS measurements in the amorphous phase of Li2Si2O5 show a narrow temperature window (700 < T < 775 K), exhibiting significant quasielastic broadening corresponding to the fast Li+ diffusion and relaxation of SiO4 units to the crystalline phase. Our INS measurements clearly show the presence of large phonon density of states (PDOS) at low energy (low-E) in the superionic amorphous phase, which disappear in the non-superionic crystalline phase, corroborating the role of low-E modes in Li+ diffusion. The frustrated energy landscape and host flexibility (due to random orientation and vibrational motion of SiO4 polyhedral units) play an essential role in diffusing the Li+. We used AIMD simulations to identify that these low-E modes involve a large amplitude of Li vibrations coupled with SiO4 vibrations in the amorphous phase. At elevated temperatures, these vibrational dynamics accelerate the Li+ diffusion via a paddle-wheel like coupling mechanism. Above 775 K, these SiO4 vibrational dynamics drive the system into the crystalline phase by locking SiO4 and Li+ into deeper minima of the free energy landscape and disappear in the crystalline phase. Both experiments and simulations provide valuable information about the atomic level stochastic and vibrational dynamics in Li2Si2O5 and their role in Li+ diffusion and vitrification.

In this manuscript, gel-combustion synthesis of Al5BO9:xTb(3+) (x = 0.0%, 0.05%, 0.1%, 0.2% and 1.5%) phosphor along with the detailed structural characterizations using a host of techniques such as XRD, SEM, EDS, IR, EXAFS and PL etc. has been reported. XRD analysis confirmed the phase pure formation and also the nanocrystalline nature of the materials. Detailed EXAFS analysis explained the oxidation state and the coordination behaviour of Tb3+ ion in the Al5BO9 matrix. PL study showed that the material can be a potential green light emitting phosphor. Thermoluminescence (TL) study revealed the presence of a wide shoulder peak and a broad dosimetry peak situating at 551 K. Net TL response from B-10 and B-11 enriched Al5BO9:0.1%Tb3+ thin pellets showed prolonged linearity within the thermal neutron fluence range of 3.2 x 10(10) to 1.6 x 10(11) n/cm(2). Also, the maximum fading of the TL signal is only 9% during the storage period of 112 days. These indicates that the developed material can be a potential candidate for dosimetry applications involving high intensity slow neutron beams. The TL glow curve was deconvoluted which revealed the presence of five individual peaks whose kinetic parameters viz. activation energy (E), order of kinetics (b) and frequency factor (s) were evaluated using both glow curve deconvolution and Chen's peak shape method and the results were found to be in good agreement.

We investigated the impact of Li stoichiometry and host flexibility on Li+ diffusion processes in LiAlGeO4 at the microscopic level using quasielastic neutron scattering (QENS) and ab initio molecular dynamics (AIMD) simulations. Using sufficiently long AIMD trajectories, we could simulate the observed QENS signal and identify the localized dynamics of Li in crystalline LiAlGeO4. Such information is vital to identify the bottleneck of diffusion processes and design materials for battery application. Our AIMD simulations in LiAlGeO4 reveal that the Li+ conductivity can be significantly improved by manipulating the Li stoichiometry and/or host flexibility via amorphization. We determined that excess Li stoichiometry enhances the Coulomb repulsion of neighboring Li sites and softens the host structure to enable faster Li+ diffusion along the hexagonal c-axis. In the amorphous structure, random orientations of AlO4 and GeO4 polyhedral units create a wide distribution of intersite distances and significantly soften the host structure, greatly enhancing the Li+ diffusion. The simulations are used to understand the nature of diffusion, especially the role of the host structure, the possible hopping pathways, and the diffusion behavior in various structures of LiAlGeO4.

We have performed quasielastic and inelastic neutron scattering (QENS and INS) measurements from 300 K to 1173 K to investigate the Na-diffusion and underlying host dynamics in Na2Ti3O7. The QENS data show that the Na atoms undergo localized jumps up to 1173 K. The ab-initio molecular dynamics (AIMD) simulations supplement the measurements and show 1-d long-ranged diffusion along the a-axis above 1500 K. The simulations indicate that the occupancy of the interstitial site is critical for long-range diffusion. The nudged-elastic-band (NEB) calculation confirmed that the activation energy barrier is lowest for diffusion along the a-axis. In the experimental phonon spectra the peaks at 10 and 14 meV are dominated by Na dynamics that disappear on warming, suggesting low-energy phonons significantly contribute to large Na vibrational amplitude at elevated temperatures that enhances the Na hopping probability. We have also calculated the mode Gr\"uneisen parameters of the phonons and thereby calculated the volume thermal expansion coefficient, which is found to be in excellent agreement with available experimental data.

A near tissue equivalent (Z(eff) = 10.8) and wide bandgap (E-g = 5.95 eV) Al(5)Bo(9): 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 Al(5)Bo(9): Mn, Li revealed the dosimetry glow peak at 542 K, which was absent in undoped Al(5)Bo(9) 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 x 10(9)-3 x 10(11) n/cm(2) 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.

We have performed quasielastic neutron scattering (QENS) experiments up to 1243 K and ab initio molecular dynamics (AIMD) simulations to investigate the Na diffusion in various phases of NaAlSiO4 (NASO), namely, low-carnegieite (L-NASO; trigonal), high-carnegieite (H-NASO; cubic) and nepheline (N-NASO; hexagonal) phases. The QENS measurements reveal Na ions localized diffusion behavior in L-NASO and N-NASO, but long-range diffusion behavior in H-NASO. The AIMD simulation supplemented the QENS measurements and showed that excess Na ions in H-NASO enhance the host network flexibility and activate the AlO4/SiO4 tetrahedra rotational modes. These framework modes enable the long-range diffusion of Na across a pathway of interstitial sites. The simulations also show Na diffusion in Na-deficient N-NASO through vacant Na sites along the hexagonal c-axis.

Long lived sealed radioactive sources are used for the energy calibration and efficiency determination of counting systems used in the nuclear sector. Using a sulphate bath, a facile electrochemical method was developed by electrodeposition of 54Mn on 5 mm (φ) stainless steel substrates for the preparation of 54Mn sources for such uses. Inactive sources prepared under suitable experimental parameters characterized by XRD revealed that manganese is deposited in oxide form. SEM and EDS analyses of electrodeposited surfaces confirmed uniform distribution of elements and the absence of fractures, flaws, and spatial variations. Cyclic voltammetry (CV) scans provided information about the electrochemical processes involved in the deposition process. Uniform distribution of radioactivity on surface of source was ascertained by autoradiography. Swipe tests of the encapsulated sources confirmed negligible removable surface contamination. The 54Mn sources containing up to 185KBq of 54Mn on stainless steel discs were prepared. These sources along with other longer lived sources were supplied to various users as a package of radiation sources for characterization of gamma counting systems over a wide energy range.