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Magnesium (Mg) alloys have a high strength/weight ratio, high dimensional stability, good machinability, and the ability to be recycled. However, their poor corrosion resistance in humid environments limits their usage for exterior aerospace components. This study aims to improve the corrosion resistance of two Mg alloys (AZ31B and AZ91) by using aluminum coatings. The latter have been deposited by a low pressure and temperature cold spray process. An aluminum powder (60 wt%) with a particle size ranging between 1 and 8 µm and nickel powder (40 wt%) with a particle size of about 70 µm were blended and used as feedstock powder. The coating thickness was about 240 μm. Its densification was achieved by the in-situ hammering effect of the nickel particles. The shot-peening effect also resulted in an enhanced coating hardness. The microstructure, mechanical properties, and corrosion resistance of the coatings have been investigated. They showed that the aluminum had a face centered cubic structure. Potentiodynamic polarization tests were performed along with a combination of materials characterization techniques to assess the corrosion resistance of the coatings when immersed in a 3.5 wt% NaCl solution for long durations. The results revealed that the corrosion resistance increased with the immersion time because of the formation of a protective oxide layer on the surface. These results were supported by elemental and structural analyses. This study shows that cold-sprayed aluminum coatings are a promising candidate for enhancing the corrosion resistance of AZ31B and AZ91Mg alloys compared to other thermal spray processes.

The tribo-mechanical properties of NiMoAl-Cr2AlC MAX phase composite coatings on stainless steel substrate have been investigated. NiMoAl with different amounts of Cr2AlC (10, 20, 50 and 100 wt.%) were prepared by turbo-mixing and deposited by High-Velocity Oxy-Fuel (HVOF) method on stainless steel substrate. The phase composition, microstructure, chemical composition, tribological and mechanical properties of the coatings were analyzed using x-Ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), Energy-Dispersive x-ray analysis (EDAX), pin-on-disk wear testing rig and nanohardness tester, respectively. The worn surfaces were analyzed by metallurgical optical microscope, FESEM and three-dimensional surface profiler to understand the wear behavior in detail. The addition of the Cr2AlC MAX phase in NiMoAl enhances the mechanical properties and reduces the surface roughness and porosity. NiMoAl-20 wt.% Cr2AlC and Cr2AlC coatings containing equal amounts of oxygen and carbon in the tribofilm show the low coefficient of friction (COF) and wear rate. The addition of the Cr2AlC MAX phase in the NiMoAl matrix up to 20 wt.% reduces the wear rate by one order of magnitude and enhances the coating life by 7000 twist fatigue cycles.

The aim is to deposit Ni-Mullite (70:30 wt%) coating on mild steel (MS) by high velocity oxy-fuel (HVOF) thermal spray process. The spraying conditions have been optimized to obtain an adherent coating of ∼110 µm thickness. The coated specimens of dimensions (20mmx20mm) had been subjected to atmospheric oxidation at different temperatures of 500°, 700°, 900° and 1000 °C. Oxidation was performed for durations of 5, 18, 30 and 45 h. The oxidized coatings have been characterized by X-Ray Diffraction (XRD) and Energy Dispersive Spectroscopy (EDAX). The oxidation rate has been studied in terms of mass gain with respect to time and temperature. It has been seen that till 700 °C, there is negligible change in the mass gain and the oxide layer thickness. Beyond 700 °C the mass gain and thickness of the oxide layer increases considerably upto a temperature of 1000 °C. The growth of the oxidized zone is seen to obey the parabolic law at high temperatures. Field Emission Scanning Electron Microscopy (FESEM) had been used to analyse the surface morphology. The as-coated specimen revealed the formation of porous nickel oxide with mullite particles distributed as fine nodular morphology. However, in oxidized specimens, formation of uniform grains containing aggregates of oxides of iron and that of wurtzite and haematite had been observed. This was also confirmed from EDAX analysis. The formation of iron oxide can be associated with the fact that iron diffuses outward to the surface resulting in oxide formation. This was reflected in the X-ray diffractogram as the highest intensity peaks in the oxidized specimen. This depicts that top surface has facilitated the oxidation of the base metal by the outward diffusion of iron atoms. Thus, to make this coating suitable for use at high temperatures, an interlayer that prevents interdiffusion of elements between the substrate and coating is required.

The aim of the present study is to develop thermally sprayable WC-12Co and WC-12Co-xAl2O3 (x = 10 and 15 wt.%) cermet coatings on steel substrate (SS 304) by high-velocity oxy fuel (HVOF) method. Influence of Al2O3 addition on the wear and corrosion behavior of WC-12Co coating has been studied. The microstructure and chemical composition of the coatings were analyzed using field emission scanning electron microscope (FESEM), and phase identification was carried out using x-ray diffraction (XRD) studies. The morphology of the coating appears as coarse granular structure. The XRD studies revealed the presence of hexagonal WC phase along with η-Co6W6C phase. It has been observed from the microhardness measurements, that the values gradually increase from 950 to 1300 HK with the addition of Al2O3 from 0 to 15 wt.%. The wear rate of WC-12Co-15Al2O3 (3.19 × 10−6 mm3/Nm) and WC-12Co-10Al2O3 (5.26 × 10−6 mm3/Nm) coatings was seen to be one order of magnitude lower than that of WC-12Co (2.9 × 10−5 mm3/Nm) coating. The polarization studies revealed that WC-12Co-15Al2O3 cermet coating showed superior corrosion protection than that of WC-12Co-10Al2O3 and WC-12Co coatings. This has been attributed to the gradual decrease in the porosity levels with an increase in Al2O3 content which is supported by morphology studies. The microhardness and wear behavior of WC-12Co-Al2O3 coatings are equivalent to those of hard chrome suggesting the possibility of its replacement.

Effect of thermal aging and chemical treatment on the physical properties of coir fiber was investigated. Coir fibers were treated with sodium hydroxide and glutaraldehyde for 2 h. The influence of alkali and aldehyde treatment on tensile strength and elongation at break was studied in detail. Enhancement in tensile strength of coir fiber was observed up to five days of aging at 50°C and further decreased. Thermal cross linking of cellulose present in the fiber may be the reason for the increase in tensile strength and thermal degradation due to the chain scission of cellulose reduced the tensile strength. Sodium-hydroxide-treated samples showed an increase in tensile strength and reduction in elongation at break. The removal of impurities such as waxy and fatty acid residues from the coir fiber by reacting with strong base solution improved the strength of fiber. Cross linking of cellulose with glutaraldehyde in the fiber reduced the elasticity and enhances the strength of the material. Scanning ...

Glasses with compositions xV(2)O(5) - (100 - x)0.8NaPO(3) - 0.2ZnO] (where 0.2

A manganese based spinel ferrite, chemically modified with polymethyl methacrylate (PMMA) and polyaniline (PANI) are synthesized and their composites are used as electromagnetic interference (EMI) shielding materials. X-ray diffraction studies show that the as-prepared manganese ferrite crystallizes in a cubic spinel structure. The particles are highly agglomerated and nanocrystalline as indicated by transmission electron microscopy. Manganese exists in +2 and +4 oxidation states and Fe in +2 and +3 oxidation states. Modified manganese ferrite and polyaniline composites in different weight ratios are evaluated for their EMI shielding properties. It is observed that composites containing the PMMA modified ferrite show enhanced total shielding effectiveness (SE T ) compared to those containing the unmodified ferrite in the X band frequency range (8-12 GHz). The optimized ratio of the PMMA modified ferrite and PANI demonstrates SE T values as high as �44 dB in the X band frequency range. © the Owner Societies.

Optically transparent hydrophobic and superhydrophobic coatings have been prepared using polyamide 12–SiO2 nanocomposite (NC) on glass substrates by the spin-coating method. The coatings have been optimized for their hydrophobicity and transparency. The transformation from hydrophobic to superhydrophobic is achieved with increase in roughness (Ra) which increases with SiO2 content. These coatings are highly transparent in the entire visible region (400–800 nm). The influence of layer thickness on water contact angle (WCA) and optical transmittance of the coatings has been studied. Field emission scanning electron micrograph (FESEM) shows the presence of SiO2 nanoparticles covered with polyamide homogenously on the surface and the particles are aggregated to form a rough structure. X-ray diffraction (XRD) patterns show that the polyamide losses its crystalline structure in the composite. The preparation procedure reported here is simple and eco-friendly. The dual nature of the coatings, that is, high transparency and superhydrophobicity in the entire visible region suggests for its potential usage in self-cleanings, wind screen and optoelectronic applications. Copyright © 2016 John Wiley & Sons, Ltd.

Cost effective and low temperature synthesis methods namely solution combustion and hydrothermal methods were used to prepare chromium incorporated nanocrystalline zinc ferrites. The effect of incorporation of low concentration Cr3+ ions on the structural, morphological, magnetic and transport properties of the zinc ferrite compounds were investigated. The crystalline nature and size variation with chromium content were valid from powder x-ray diffraction. Particles size and crystallite size variation were valid from scanning electron microscopy and transmission electron microscopy respectively. With the increase in chromium incorporation, the crystallite and particles sizes were decreased. Fourier transform infrared spectroscopy (FTIR) studies confirmed the presence of strong metal-oxygen bonds. The elastic properties of the materials in both the methods were estimated by FTIR studies. Magnetic properties namely saturation magentization, remanent magnetization and coercivity values were decreased with increase in Cr3+ ions concentration. The dielectric properties of the samples decreased with increase in the Cr3+ ions. The dielectric constant was observed to be of the order of 10(6) at low frequency and almost 1 at higher frequency range. The activation energy estimated using Arrhenius plots was of the order of 0.182 eV and 0.368 eV respectively for the compounds prepared by solution combustion and hydrothermal methods. The emission spectra of the samples excited at 344 nm were reported using photoluminescence (PL) spectroscopy. Further, the approximate energy band gap(E-g) was estimated from PL studies. The E-g of the materials were lie in the range of 2.11-1.98 eV. (C) 2015 Elsevier B.V. All rights reserved.

One-dimensional (1D) zinc oxide (ZnO) hexagonal rods have been successfully synthesized by surfactant free hydrothermal process at different temperatures. It can be found that the reaction temperature play a crucial role in the formation of ZnO uniform hexagonal rods. The possible formation processes of 1-D ZnO hexagonal rods were investigated. The zinc hydroxide acts as the morphology-formative intermediate for the formation of ZnO nanorods. Upon excitation at 325 nm, the sample prepared at 180 °C show several emission bands at 400 nm (∼3.10 eV), 420 nm (∼2.95 eV), 482 nm (∼2.57 eV) and 524 nm (∼2.36 eV) corresponding to different kind of defects. TL studies were carried out by pre-irradiating samples with γ-rays ranging from 1 to 7 kGy at room temperature. A well resolved glow peak at ∼354 °C was recorded which can be ascribed to deep traps. Furthermore, the defects associated with surface states in ZnO nano-structures are characterized by electron paramagnetic resonance.

CdSiO 3 :Eu 3+ (0.5–5 mol%) nanophosphors were synthesized using oxalyl di-hydrazide fuel by solution combustion technique for the first time . The structural, thermo and photoluminescent properties were studied. The average particle size was estimated from transmission electron microscopy (TEM) studies and found to be in the range 20–30 nm. The values were in good agreement with Scherer’s method and Williamson–Hall plots. Scanning electron microscope (SEM) showed highly porous, fluffy and many agglomerated particles. Photoluminescence (PL) CdSiO 3 :Eu 3+ (0.5–5 mol%) shows emission peaks at 577, 596, 612, 659 and 706 nm which were assigned to 5 D 0 → 7 F j (j = 0, 1, 2, 3, 4) transition respectively. It was observed that PL intensity increases up to the concentration 4 mol% Eu 3+ . Thermoluminescence (TL) studies were carried out on CdSiO 3 :Eu 3+ (1–5 mol%) nanophosphor by exposing to γ-rays (1–6 kGy) and UV (5–25 min) respectively. The TL intensity was found to be highest in 1 mol% Eu 3+ concentration. Further, effect of different gamma (1–6 kGy) and UV (5–25 min) exposure was studied on CdSiO 3 :Eu 3+ nanophosphor. Simple well resolved glow peak at ∼178 °C was recorded for both the exposures. The TL intensity at 178 °C increase linearly with increase in the γ-dose. However, in UV exposed samples the TL glow peak intensity increase up to 10 min and thereafter the peak intensity decreases with further increase in exposure time. The effect of heating rate (β) and fading characteristics for γ and UV were studied in CdSiO 3 :Eu 3+ (1 mol%). The kinetic parameters ( E , b , s ) were estimated using different theoretical methods.

ZnO:Eu (0.1 mol%) nanopowders have been synthesized by auto ignition based low temperature solution combustion method. Powder X-ray diffraction (PXRD) patterns confirm the nanosized particles which exhibit hexagonal wurtzite structure. The crystallite size estimated from Scherrer’s formula was found to be in the range 35–39 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies reveal particles are agglomerated with quasi-hexagonal morphology. A blue shift of absorption edge with increase in band gap is observed for Eu doped ZnO samples. Upon 254 nm excitation, ZnO:Eu nanopowders show peaks in regions blue (420–484 nm), green (528 nm) and red (600 nm) which corresponds to both Eu 2+ and Eu 3+ ions. The electron paramagnetic resonance (EPR) spectrum exhibits a broad resonance signal at g = 4.195 which is attributed to Eu 2+ ions. Further, EPR and thermoluminescence (TL) studies reveal presence of native defects in this phosphor. Using TL glow peaks the trap parameters have been evaluated and discussed.

Rod like structures of hexagonal Y(OH) 3 :Ni 2+ and cubic Y 2 O 3 :Ni 2+ phosphors have been successfully synthesized by solvothermal method. X-ray diffraction studies of as-formed product shows hexagonal phase, whereas the product heat treated at 700 °C shows pure cubic phase. Scanning electron micrographs (SEM) of Y(OH) 3 :Ni 2+ show hexagonal rods while Y 2 O 3 :Ni 2+ rods were found to consist of many nanoparticles stacked together forming multi-particle-chains. EPR studies suggest that the site symmetry around Ni 2+ ions is predominantly octahedral. PL spectra show emission in blue, green and red regions due to the 3 T 1 ( 3 P)→ 3 A 2 ( 3 F), 1 T 2 ( 1 D)→ 3 A 2 ( 3 F) and 1 T 2 ( 1 D)→ 3 T 2 ( 3 F) transitions of Ni 2+ ions, respectively. TL studies were carried out for Y(OH) 3 :Ni 2+ and Y 2 O 3 :Ni 2+ phosphor upon γ-dose for 1–6 kGy. A single well resolved glow peaks at 195 and 230 °C were recorded for Y(OH) 3 :Ni 2+ and Y 2 O 3 :Ni 2+ , respectively. The glow peak intensity increases linearly up to 4 kGy and 5 kGy for Y(OH) 3 :Ni 2+ and Y 2 O 3 :Ni 2+ , respectively. The kinetic parameters such as activation energy ( E ), frequency factor ( s ) and order of kinetics ( b ) were estimated by different methods. The phosphor follows simple glow peak structure, linear response with gamma dose, low fading and simple trap distribution, suggesting that it is quite suitable for radiation dosimetry.

MgSrAl10O17:Cr3+ powder phosphor has been synthesized by a solution combustion method at furnace temperature of 500 °C in a short time (

Manganese-doped LaMgAl11O19 powder has been prepared by an easy combustion method. Powder x-ray diffraction and scanning electron microscopy have been used to characterize the as-prepared phosphor. The electron paramagnetic resonance (EPR) spectrum of LaMgAl11O19:Mn2+ phosphor exhibits six-line hyperfine structure centered at g ≈ 1.973. The number of spins participating in resonance (N) and the paramagnetic susceptibility (χ) for the resonance signal at g ≈ 1.973 have been calculated as a function of temperature. The photoluminescence spectrum exhibits green emission at 516 nm, which is attributed to 4T1 → 6A1 transition of Mn2+ ions. From EPR and luminescence studies, it is observed that Mn2+ ions occupy Mg2+ sites and Mn2+ ions are located at tetrahedral sites in the prepared phosphors.

Gd1.96−xYxEu0.04O3 (x = 0.0, 0.49, 0.98, 1.47, 1.96 mol%) nanophosphors were synthesized by propellant combustion method at low temperature (400 °C). The powder X-ray diffraction patterns of as formed Gd1.96Eu0.04O3 showed monoclinic phase, however with the addition of yttria it transforms from monoclinic to pure cubic phase. The porous nature increases with increase of yttria content. The particle size was estimated from Scherrer’s and W–H plots which was found to be in the range 30–40 nm. These results were in well agreement with transmission electron microscopy studies. The optical band gap energies estimated were found to be in the range 5.32–5.49 eV. PL emission was recorded under 305 nm excitation show an intense emission peak at 611 nm along with other emission peaks at 582, 641 nm. These emission peaks were attributed to the transition of 5D0 → 7FJ (J = 0, 1, 2, 3) of Eu3+ ions. It was observed that PL intensity increases with increase of Y content up to x = 0.98 and thereafter intensity decreases. CIE color co-ordinates indicates that at x = 1.47 an intense red bright color can be achieved, which could find a promising application in flat panel displays. The cubic and monoclinic phases show different thermoluminescence glow peak values measured under identical conditions. The response of the cubic phase to the applied dose showed good linearity, negligible fading, and simple glow curve structure than monoclinic phase indicating that suitability of this phosphor in dosimetric applications.

CaTiO3:Sm3+ (1-11 mol%) nanophosphors were successfully synthesized by a low temperature solution combustion method LCS]. The structural and morphological properties of the phosphors were studied by using Powder X-ray diffractometer (PXRD), Fourier transform infrared (FTIR), X-ray photo electron spectroscopy (XPS), scanning electron microscope (SEM) and transmission electron microscopy (TEM). TEM studies indicate that the size of the phosphor is similar to 20-35 nm. Photoluminescence (PL) properties of Sm3+ (1-11 mol%) doped CaTiO3 for NUV excitation (407 nm) was studied in order to investigate the possibility of its use in White light emitting diode (WLED) applications. The emission spectra consists of intra 4f transitions of Sm3+, such as (4)G(5/2) -> H-6(5/2) (561 nm), (4)G(5/2) -> H-6(7/2) (601-611 nm), (4)G(5/2) -> H-6(9/2) (648 nm) and (4)G(5/2) -> H-6(11/2) (703 nm) respectively. Further, the emission at 601-611 nm show strong orange-red emission and can be applied to the orange-red emission of phosphor for the application for near ultra violet (NUV) excitation. Thermoluminescence (TL) of the samples irradiated with gamma source in the dose range 100-500 Gy was recorded at a heating rate of 5 degrees C s(-1). Two well resolved glow peaks at 164 degrees C and 214 degrees C along with shouldered peak at 186 degrees C were recorded. TL intensity increases up to 300 Gy and thereafter, it decreases with further increase of dose. The kinetic parameters namely activation energy (E), frequency factor (s) and order of kinetics were estimated and results were discussed in detail. (C) 2014 Elsevier B.V. All rights reserved.

A series of Eu3+ (1–6 mol%) activated YAlO3 nanophosphors have been synthesized by a low temperature solution combustion method using ODH fuel. The structural, morphological, thermo and photoluminescent properties are studied. Powder X-ray diffraction patterns indicate that the phosphors are orthorhombic phase of YAlO3 with small traces of Y3Al5O12 phase. Scanning Electron micrographs show the crystallites are fused together to form dumbbell shape. Transmission Electron micrograph shows the crystallites are nano size in the range 30–45 nm. Photoluminescence studies of Eu doped YAlO3 showed orange red emission (CIE co-ordinates x = 0.645, y = 0.353) due to the 5D0→7Fj (j = 0, 1, 2, 3, 4) transitions of Eu3+ ions. The concentration quenching occurs at x = 5 mol%. YAlO3:Eu3+ (5 mol%) exhibit two thermoluminescence (TL) glow peaks around 229 and 324 °C respectively. TL response with different γ-doses show a good linear response and low fading suggesting that Eu3+ activated YAlO3 is suitable for radiation dosimetry applications. The kinetic parameters (E, b, s) are estimated using peak shape method and discussed in detail.

Thermally stable superhydrophobic coatings have been prepared using Polyvinylidene fluoride (PVDF)Multiwalled carbon nanotubes (MWCNTs) by spray coating method. The effects of MWCNT (0 – 66 wt%) and temperature (300 to 623 K) on wettability have been studied. A transformation from hydrophobic to superhydrophoic state was achieved with increase of CNT content. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) studies reveal that with increase in CNT content, -phase of PVDF decreases suggesting that MWCNT has strong effect on the phase separation of PVDF. Field emission scanning electron microscopy (FESEM) studies show that the coatings have rough surface with porous structure. With increase in CNT content the protrusion like structures decreased reaching micro/nano scales. The coatings were thermally stable upto 573 K exhibiting superhydrophobicity and thereafter transformed to superhydrophilic state at 623 K. Energy dispersive X-ray spectroscopy (EDXS) analysis show the absence of fluorine after annealing at 623 K suggesting decomposition of PVDF. X-ray photoelectron spectroscopy (XPS) of C1s and F1s core levels in as-deposited PVDFMWCNT coating show the presence of CF2 related species. Concentration of fluorine drastically decreases after heat treatment of the coating at 350 C. The main advantage of the present method is feasibility for application over large area and the coatings are stable upto 573 K.

The structural, magnetic and dielectric properties of nano zinc ferrite prepared by the propellant chemistry technique are studied. The PXRD measurement at room temperature reveal that the compound is in cubic spinel phase, belong to the space group Fd − 3m. The unit cell parameters have been estimated from Rietveld refinement. The calculated force constants from FTIR spectrum corresponding to octahedral and tetrahedral sites at 375 and 542 cm −1 are 6.61×10 2 and 3.77×10 2 N m −1 respectively; these values are slightly higher compared to the other ferrite systems. Magnetic hysteresis and EPR spectra show superparamagnetic property nearly to room temperature due to comparison values between magnetic anisotropy energy and the thermal energy. The calculated values of saturation magnetization, remenant magnetization, coercive field and magnetic moment supports for the existence of multi domain particles in the sample. The temperature dependent magnetic field shows the spin freezing state at 30 K and the blocking temperature at above room temperature. The frequency dependent dielectric interactions show the variation of dielectric constant, dielectric loss and impedance as similar to other ferrite systems. The AC conductivity in the prepared sample is due to the presence of electrons, holes and polarons. The synthesized material is suitable for nano-electronics and biomedical applications.

A simple and inexpensive combustion method was used to prepare Fe3+ doped YAlO3 perovskite within few minutes at low temperature (400 ± 10 °C). This might be useful in lowering the cost of the material. The final products were well characterized by various spectroscopic techniques such as PXRD, SEM, TEM, FTIR and UV–Visible. The average crystallite size was estimated from the broadening of the PXRD peaks and found to be in the range 45–90 nm, the results were in good agreement with the W–H plots and TEM. The crystallites show dumbbell shape, agglomerated particles with different size. The TL glow curves of 1–5 kGy γ-irradiated YAlO3:Fe3+ (0.1 mol%) nanopowder warmed at a heating rate of 3 °C s−1 records a single glow peak at ∼260 °C. The kinetic parameters namely activation energy (E), order of kinetics (b) and frequency factor (s) were determined at different gamma doses using the Chens glow peak shape method and the results were discussed in detail. The photoluminescence spectra for Fe3+ (0.1–0.9 mol%) doped YAlO3 records the lower energy band at 720 nm (4T1 (4G) → 6A1 (6S)) and the intermediate band located at 620 nm (4T2 (4G) → 6A1 (6S)) with the excitation of 378 nm. The higher energy band located at 514 nm was associated to 4E + 4A1 (4G) → 6A1 (6S) transition. The resonance signals at g values 7.6, 4.97, 4.10, 2.94, 2.33 and 1.98 were observed in EPR spectra of Fe3+ (0.1–0.9 mol%) doped YAlO3 recorded at room temperature. The g values indicate that the iron ions were in trivalent state and distorted octahedral site symmetry was observed.

A series of red light emission phosphors of Sr 2 SiO 4 :Eu 3+ (1–5 mol%) and Sr 2 SiO 4 :Eu 3+ :M + (M + = Na + , K + and Li + ) were prepared through simple low temperature solution combustion method and their luminescence properties were studied. The powder X-ray diffraction (XRD) results revealed the formation of highly crystalline Sr 2 SiO 4 :Eu 3+ nanophosphor having an average particle size 45–60 nm and strain was measured to be (2.4–3.1) × 10 3 . The SEM pictures of Sr 2 SiO 4 :Eu 3+ and Sr 2 SiO 4 :Eu 3 + : M + showed porous in nature and irregular shaped particles. The phosphors can be effectively excited by the light of 395 nm and show the characteristic emission peaks assigned to transitions of 5 D 0 → 4 F J ( J = 0, 1, 2, 3, 4). The excitation and emission spectra indicate that the phosphors can be effectively excited by UV (∼395 nm) light which emits an intense red light peaked at ∼614 nm. The Eu 3+ concentration quenching mechanism was verified to be multipole–multipole interaction and critical energy transfer distance ( R C ) was 16.43 nm. The effects of different concentration of Eu 3+ and charge compensations on luminescence properties were discussed. The highest PL intensity was recorded for 4 mol% Eu 3+ ions. Further, Li + (0.03) has the best charge compensation effect followed by Na + and K + respectively. The γ-induced studies showed three glow peaks at 211, 163 and 243 (shouldered peaks) respectively at a warming rate of 5 °C s −1 . The glow peak intensity at 163 °C increases linearly up to 3 kGy and after that it decreases. Up to 3 kGy, the phosphor was quite useful for radiation dosimetry.

Thermoluminescence properties of YAlO3:Dy3+ nanophosphor prepared by a low temperature solution combustion (SC) method using oxalyl dihydrazide as a fuel were studied and the results were compared to bulk phosphor prepared by solid state (SS) synthesis. Powder X-ray diffraction patterns confirm the orthorhombic phase of SC and SS methods. Rietveld refinement was used to estimate the cell parameters of undoped and Dy3+ doped YAlO3. Scanning electron micrographs reveal dumbbell shape particles. Electron paramagnetic resonance spectra of YAlO3:Dy3+ nanophosphors were studied at 293 K, 77 K and 10 K. Thermoluminescence responses of SC and SS prepared phosphor were studied using gamma irradiation in the dose range 0.1-6 kGy at a warming rate of 1 degrees C s (1) at room temperature (RT). The optimized concentrations of Dy3+ ions in YAlO3 was found to be 3 mol%. The trapping parameters (i. e. activation energy, frequency factor, order of kinetic) of all the individual peaks of the glow curves have been analysed by using Chen's method. The low fading and linear response in the wide range (0.1-1 kGy) suggests the possibility of usage of SC prepared phosphor in dosimeter applications. (C) 2013 Elsevier B. V. All rights reserved.

For the first time, CdSiO3:Tb3+ (1–9 mol%) nanophosphor were prepared by solution combustion method using oxalyl dihydrazide (ODH) as a fuel. Monoclinic phase formation was confirmed by powder X-ray diffraction. The average crystallite sizes calculated by Debye–Scherrer formula, Williamson–Hall (W–H) plot and Transmission electron microscopic studies were in the range of 28–40 nm. The scanning electron microscopic images confirm the porous nature of the samples. The photoluminescence (PL) emission spectra shows the characteristic Tb3+ ion peaks at 488, 542, 584 and 622 nm corresponding to 5D4 → 7FJ (J = 3, 4, 5 and 6) transitions for all the compositions excited at 270 nm. The maximum PL intensity was observed for 7 mol% of Tb3+ ions. The critical energy transfer distance was found to be 12.18 Ǻ. The quenching was observed with increase in concentration of Tb3+ may be due to dipole–dipole interaction. The chromaticity co-ordinates of all the phosphors were well located in green region. A well resolved Thermoluminescence (TL) glow peak at 150 °C was observed in all the UV exposed samples. The maximum TL intensity was observed for 9 mol% of Tb3+ doped samples. The variation of UV exposure (1–15 min) on TL glow curves of CdSiO3:Tb3+ nanophosphor showed sub-linear behavior supported by track interaction model (TIM).

The nano ZnFe2O4 compound was prepared by eco-friendly hydrothermal method. The characterization of the sample for its structure, morphology and composition were done by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), dynamic light scattering, Fourier transform infrared spectroscopy, zeta surface profiler and UV–Visible spectroscopy studies. The PXRD measurement reveals that the compound shows spinel cubic phase belong Fd 3 ¯ m (227) space group. Morphology of the compound from SEM and surface profile shows nearly spherical agglomerated particles with well defined grains and grain boundaries. The material shows the semiconducting behavior with Eg of 2.3 eV at room temperature (RT). The variation in the magnetic ordering was observed for wide range of temperature. The compound behaves like a soft magnetic material with ferrimagnetic at various temperatures except at RT. Both magnetic and EPR studies supports the superparamagnetic behavior of the the sample. The DC conductivity, dielectric and AC conductivity behavior of the 1000 °C pellets sintered for 2 h shows good frequency dependent transport properties. The present study facilitate in selecting the suitable materials for the nanoelectronics and spintronic applications.

Despite being a particularly good emitter, use of divalent Eu has been seriously limited. This is because severe reducing environments or special hosts are needed during synthesis of divalent Eu containing phosphors. In this work we stabilize Eu in its 2+ state (in CaAl2O4) using an open-air solution combustion reaction. The impact of fuel (F) to oxidizer (O) molar ratios (F/O = 0.5-2.0) on luminescence properties is explored. Chromaticity of Eu:CaAl2O4 depends sensitively on the F/O ratio. In general, higher F/O inhibits Eu3+ and promotes Eu2+ formation, which in turn improves the quality of the blue phosphor. EPR spectra show inhomogeneous broadening effects with the increase in F/O ratio, which suggests that disorder creation is promoted when F/O is increase. This is also confirmed by an increase in emission line width in PL spectra, when F/O is increased. (C) 2013 Elsevier B.V. All rights reserved.

We present a simple route for synthesis of Y2O3 for both photoluminescent (PL) and thermoluminescent (TL) applications. We show that by simply switching the fuel from ethylene di-amine tetracetic acid (EDTA) to its disodium derivative (Na-2-EDTA), we obtain a better photoluminescent material. On the other hand, use of EDTA aids in formation of Y2O3 which is a better thermoluminescent material. In both cases pure cubic nano-Y2O3 is obtained. For both the material systems, structural characterization, photoluminescence, thermoluminescence, and absorbance spectra are reported and analyzed. Use of EDTA results in nano Y2O3 with crystallite size similar to 10 nm. Crystallinity improves, and crystallite size is larger (similar to 30 nm) when Na-2-EDTA is used. TL response of Y2O3 nanophosphors prepared by both fuels is examined using UV radiation. Samples prepared with EDTA show well resolved glow curve at 140 degrees C, while samples prepared with Na-2-EDTA shows a glow curve at 155 degrees C. Effect of UV exposure time on TL characteristics is investigated. The TL kinetic parameters are also calculated using glow curve shape method. Results indicate that the TL behavior of both the samples follow a second order kinetic model. (C) 2013 Elsevier B.V. All rights reserved.

The effect of TiO 2 (5, 10 and 15 mg) nano-particles on optical, electrical and mechanical properties of Poly (vinyl alcohol) (PVA) films were reported. The un-doped PVA films showed high transmittance in the visible region, however with the increase of TiO 2 doping the transmittance has decreased. The films with sandwich structures of the type Al-PVA-Al and Al-PVA-TiO 2 -Al were fabricated to study its electrical properties. The current-voltage (I-V) characteristics show the leakage current density in PVA film slightly decreases with the addition of TiO 2 . The Raman spectrum shows characteristic scattering peaks of the PVA film at 1432, 1145, 920 and 852cm−1 and the peak observed at 637 cm−1 is attributed to anatase phase of TiO 2 . The mechanical properties of the films were improved substantially with the doping of TiO 2 nano-particles and the mechanism responsible for the improved strength is explained in detail.

The mechanical, thermal, and optical properties, along with the microstructure and electron paramagnetic resonance (EPR) spectra, have been studied for MgAl 2 O 4 :Cr 3+ spinel glass and glass–ceramics. The activation energy of the crystallization has been estimated from the differential scanning calorimetry (DSC) study using different models and is found to vary within 255–270 kJ/mol for the un-doped precursor glass. The microstructure of the glass–ceramics has been characterized using field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The TEM images demonstrate the presence of cubic crystals in the glass–ceramics of uniform size 10–15 nm. X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy reveal the presence of MgAl 2 O 4 spinel as the only crystalline phase, formed in the heat-treated glass–ceramics. The EPR spectrum of Cr 3+ doped glass sample exhibits a broad resonance signal with effective g = 1.97 whereas in glass–ceramic sample an additional weak resonance signal is observed at g = 3.83. The excitation spectrum exhibits two bands in the visible region. The emission spectrum exhibits an intense red emission at 690 nm which is characteristic of Cr 3+ ions caused by the spin-forbidden 2 E g → 4 A 2g transition. All the mechanical properties are found to have improved in the glass–ceramics when compared to glasses. A good combination of micro-hardness (∼6.0 GPa), high fracture toughness (∼5.0 MPa m 1/2 ), 3 point flexural strength (∼100 MPa) and elastic modulus (∼55 GPa) has been obtained for the glass–ceramic samples.

The present study aims to develop dense FeCoCrNi2Al high entropy alloy (HEA) coating of thickness ≅ 200 μm by high velocity oxy-fuel (HVOF) process. Studies on the microstructure and mechanical properties like microhardness, erosion resistance of the HVOF coated FeCoCrNi2Al HEA has not been reported by any investigator. An adherent coating has been deposited displaying a lamellar microstructure. The X-ray diffractogram of the coating revealed the formation of a major FCC and a minor BCC phase with small amount of oxide. The oxide phase was confirmed to be Al2O3 using Raman spectroscopy. The microhardness of the coating is found to be 600 ± 30 VHN with no crack formation upto a load of 1 kgf. The erosion resistance of the HEA coated steel was evaluated upto a temperature of 800 °C. The coating displays good erosion resistance and the depth of penetration of the erodent was well within the coating thickness with no delamination of the coating, thereby making it suitable for high temperature applications.

Structural, iono (IL) and thermoluminescence (TL) studies of Zn 2 SiO 4 :Sm 3+ (1–5 mol%) nanophosphor bombarded with swift heavy ions in the fluence range 3.91×10 12 –21.48×10 12 cm −2 have been carried out. The average crystallite sizes for pristine and ion irradiated for 3.91×10 12 ions cm −2 and 21.48×10 12 ions cm −2 were found to be 34, 26 and 20 nm. With increase of ion fluence, the intensity of XRD peaks decreases and FWHM increases. The peak broadening indicates the stress induced point/clusters defects produced due to heavy ion irradiation. IL studies were carried out for different Sm 3+ concentrations in Zn 2 SiO 4 by irradiating with ion fluence of 15.62×10 12 ions cm −2 . The characteristic emission peaks at ∼562, 599, 646 and 701 nm were recorded by exciting Si 7+ ions in the fluence range 3.91×10 12 –21.48×10 12 ions cm −2 . These peaks were attributed to 4 G 5/2 → 6 H 5/2 (562 nm), 4 G 5/2 → 6 H 7/2 (599 nm), 4 G 5/2 → 6 H 9/2 (646 nm), and 4 G 5/2 → 6 H 5/2 (701 nm) transitions of Sm 3+ . The highest emission was recorded at 3 mol% of Sm 3+ doped Zn 2 SiO 4 . TL studies were carried out for 3 mol% Sm 3+ concentration in the fluence range 3.91×10 12 –21.48×10 12 ions cm −2 . Two TL glow peaks at 152 and 223 °C were recorded. The kinetic parameters ( E , b , and s ), were estimated using Chen's peak shape method. Simple glow curve structure (223 °C), highly resistive, increase in TL intensity up to 19.53×10 12 ions cm −2 , simple trap distribution makes Zn 2 SiO 4 :Sm 3+ (3 mol%) phosphor highly useful in radiation dosimetry.

Glass of the composition 23B 2 O 3 –5ZnO–72Bi 2 O 3 – x CuO (where, x =0.0003, 0.0012 and 0.003 at%, in excess) were prepared by a melt-quench technique. The effects of the copper ions on the structural and optical properties of ZnO–Bi 2 O 3 –B 2 O 3 glass matrix were analyzed using various spectroscopic techniques. The infrared spectra showed the presence of some bands that are assigned to vibrations of Bi–O bonds from BiO 6 octahedral units and B–O bonds from BO 3 and BO 4 units. The electron paramagnetic resonance spectra revealed the presence of Cu 2+ ions in the glass structure in an axially distorted octahedral environment. The number of Cu 2+ ions participating in resonance and its paramagnetic susceptibility has been evaluated. The UV–vis spectra show a broad absorption band at 785 nm and another band at 438 nm which are due to d-d transitions of Cu 2+ ions. These glasses are found to exhibit visible and near infrared luminescence bands centered at 548 and 652, and 804 nm when excited at 400 and 530 nm, respectively. The luminescence centers are supposed to be caused by the lower valence state of bismuth, such as Bi 2+ and Bi + ions, generated during in-situ redox reactions.

Nanocrystalline Ca 2 SiO 4 :Eu 3+ (1–5 mol%) phosphors have been prepared by solution combustion process using DFH as a fuel which is less temperature compared to solid state route. The powders were well characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Fourier Transform Infra-Red (FTIR) spectroscopy. PXRD results confirm the β-Ca 2 SiO 4 phase upon calcination at 950 °C for 3 h. SEM micrographs indicate that the product is highly porous and agglomerated particles. Thermoluminescence (TL) studies have been carried out with γ-irradiation in the dose range 1–6 kGy. Two TL glow peaks are recorded at ∼439 and ∼536 K for all the Eu 3+ concentrations (1–5 mol%), the highest TL glow peak intensity was recorded for 4 mol% Eu 3+ . The 439 K glow peak increases linearly with γ-dose whereas, 536 K glow peak follows sublinear. The kinetic parameters ( E , b , s ) have been estimated from different methods. Further, 439 K TL glow peak show good linearity, hence it is quite useful in radiation dosimetry. The PL spectra consists of series of peaks at 565–580, 590, 613–618, 652–681 nm respectively upon excited at different excitation wavelengths. These peaks are attributed to the transitions 5 D 0 → 7 F 0 , 5 D 0 → 7 F 1 , 5 D 0 → 7 F 2 , 5 D 0 → 7 F 2 , 5 D 0 → 7 F 3 and 5 D 0 → 7 F 4 respectively. The chromaticity co-ordinates of the Eu 3+ activated samples are located in white light and hence the phosphor is highly useful for white LED’s.

CoFe 2 O 4 nanoparticles were prepared by solution combustion method. The nanoparticle are characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). PXRD reveals single phase, cubic spinel structure with Fd 3 ¯ m (227) space group. SEM micrograph shows the particles are agglomerated and porous in nature. Electron paramagnetic resonance spectrum exhibits a broad resonance signal g =2.150 and is attributed to super exchange between Fe 3+ and Co 2+ . Magnetization values of CoFe 2 O 4 nanoparticle are lower when compared to the literature values of bulk samples. This can be attributed to the surface spin canting due to large surface-to-volume ratio for a nanoscale system. The variation of dielectric constant, dielectric loss, loss tangent and AC conductivity of as-synthesized nano CoFe 2 O 4 particles at room temperature as a function of frequency has been studied. The magnetic and dielectric properties of the samples show that they are suitable for electronic and biomedical applications.

The Y2O3:Ho3+ powder phosphors have been prepared by using low temperature combustion method. Powder X-ray diffraction, scanning electron microscope and transmission electron microscopy techniques were used to characterize the as-prepared phosphor. The UV–Vis-NIR absorption, excitation and emission studies have been performed and the phenomenological Judd–Ofelt intensity parameters which are critically important in calculating the radiative properties and stimulated emission crosssection have been calculated by using Judd–Ofelt theory. Based on the calculated values of the inter electronic parameter, covalency and bonding parameter the bonding between the Ho3+ ions and surrounding oxygen atoms have been found to be covalent in nature. The color purity has also been verified by using the chromaticity diagram. The analysis shows that the Y2O3:Ho3+ phosphor may be used for producing the green light emitting diodes and display applications.

Calcium titanate (CaTiO3) nanophosphors were synthesized by three different routes namely solution combustion (SC), modified solid-state reaction (MSS) and solid-state (SS) methods. Rietveld refinement studies revealed the presence of an orthorhombic structure with traces of CaCO3. The crystallite sizes were found to be in the 43-45 nm range. TEM studies also confirm the nano size with well crystalline nature. EPR spectrum for SS method exhibits a broad resonance signal at g = 2.027 is attributed to TiO6](9-) center, whereas in MSS sample the resonance signals are attributed to surface electron and hole trapping sites. The TL behavior has been investigated for the first time using gamma-irradiation. TL glow peak at 169 degrees C were recorded in CaTiO3 prepared by SC, MSS and SS methods. The trapping parameters such as activation energy (E) and order of kinetics (b) were estimated using peak shape method and results are discussed in detail. (C) 2013 Elsevier Ltd. All rights reserved.

YAlO3:Ni2+ (0.1 mol%) doped nanophosphor was synthesised by a low temperature solution combustion method. Powder X-ray diffraction (PXRD) confirms the orthorhombic phase of yttrium aluminate (YAlO3) along with traces of Y3Al5O12. Scanning Electron microscopy (SEM) shows that the powder particles appears to be spherical in shape with large agglomeration. The average crystallite sizes appeared to be in the range 45-90 nm and the same was confirmed by transmission electron microscopy (TEM) and Williamson-Hall (W-H) plots. Electron Paramagnetic Resonance (EPR) and photoluminescence (PL) studies reveal that Ni2+ ions are in octahedral coordination. Thermoluminescence (TL) glow curve consists of two peaks with the main peak at similar to 224 degrees C and a shouldered peak at 285 degrees C was recorded in the range 0.2-15 kGy gamma-irradiated samples. The TL intensity was found to be increasing linearly for 224 degrees C and 285 degrees C peaks up to 1 kGy and thereafter it shows sub-linear (up to 8 kGy) and saturation behavior. The trap parameters namely activation energy (E), order of kinetics (b), frequency factor (s) at different gamma-doses were determined using Chens glow peak shape and Luschiks methods then the results are discussed in detail. Simple glow peak structure, the 224 degrees C peak in YAlO3:Ni2+ nanophosphor can be used in personal dosimetry. (C) 2012 Elsevier B.V. All rights reserved.

α-Fe(2)O(3) nanoparticles were synthesized by a low temperature solution combustion method. The structural, magnetic and luminescence properties were studied. Powder X-ray diffraction (PXRD) pattern of α-Fe(2)O(3) exhibits pure rhombohedral structure. SEM micrographs reveal the dumbbell shaped particles. The EPR spectrum shows an intense resonance signal at g≈5.61 corresponding to isolated Fe(3+) ions situated in axially distorted sites, whereas the g≈2.30 is due to Fe(3+) ions coupled by exchange interaction. Raman studies show A(1g) (225 cm(-1)) and E(g) (293 and 409 cm(-1)) phonon modes. The absorption at 300 nm results from the ligand to metal charge transfer transitions whereas the 540 nm peak is mainly due to the (6)A(1)+(6)A(1)→(4)T(1)(4 G)+(4)T(1)(4 G) excitation of an Fe(3+)-Fe(3+) pair. A prominent TL glow peak was observed at 140°C at heating rate of 5 °Cs(-1). The trapping parameters namely activation energy (E), frequency factor (s) and order of kinetics (b) were evaluated and discussed.

Nano-ceramic phosphor CaSiO 3 doped with Pb and Mn was synthesized by the low temperature solution combustion method. The materials were characterized by Powder X-Ray Diffraction (XRD), Thermo-gravimetric and Differential Thermal Analysis (TG-DTA), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The Electron Paramagnetic Resonance (EPR) spectrum of the investigated sample exhibits a broad resonance signal centered at g=1.994. The number of spins participating in resonance (N) and its paramagnetic susceptibility (I�) have been evaluated. Photoluminescence of doped CaSiO 3 was investigated when excited by UV radiation of 256 nm. The phosphor exhibits an emission peak at 353 nm in the UV range due to Pb 2+. Further, a broad emission peak in the visible range 550-625 nm can be attributed to 4T 1� 6A 1 transition of Mn 2+ ions. The investigation reveals that doping perovskite nano-ceramics with transition metal ions leads to excellent phosphor materials for potential applications. © 2012 Elsevier Ltd and Techna Group S.r.l.

An intense infrared emitting MgSrAl 10 O 17 :Er 3+ phosphor co-doped with Yb 3+ , Ba 2+ and Ca 2+ ions have been prepared by a solution combustion method. Phase purity of the derived compounds was confirmed by X-ray diffraction technique. The vibrational properties of MgSrAl 10 O 17 phosphor was studied by Fourier transform infrared spectroscopy. The broad and strong infrared emission of Er 3+ ions at around 1.53 μm was observed upon excitation at 980 nm. Effect of co-doping with the Yb 3+ , Ba 2+ and Ca 2+ ions on the infrared luminescence intensity of Er 3+ ions and the mechanism responsible for the variation in the infrared intensity have been discussed. The results indicate that these materials may be suitable for the optical telecommunication window and wavelength division multiplexing applications.

This work reports the preparation of CdSiO3:Sm3+ (1–7 mol%) nanophosphors by a low temperature solution combustion method. For the first time the effect of NaF flux on the crystallization behavior, morphology, and thermoluminescence property of 5 mol% Sm3+ doped CdSiO3 has been investigated. The nanopowders are well characterized by powder X-ray diffraction (PXRD), Fourier Transform Infra-Red (FT–IR), and scanning electron microscopy (SEM). PXRD results indicate that the powder calcined at 800 °C for 2 h has monoclinic phase. SEM results show that the powder is highly porous and the pore size and shape can be modified by the addition of NaF flux. Addition of NaF could lead to formation of particle type morphology and the increase in wt% of NaF changes crystallinity and phase. The thermoluminescence glow curves for 2–6 wt% NaF in CdSiO3:Sm3+ show a single, well resolved glow peak at 126, 130 and 150 °C, respectively. But for the sample prepared with 8 wt% of NaF flux shows two glow peaks at 148 and 220 °C. With the addition of NaF flux, TL intensity can be effectively enhanced.

This work explores the preparation of nanocrystalline Ce 3+ (1–9 mol%) doped CdSiO 3 phosphors via solution combustion process and its thermoluminescence (TL) behavior upon UV and swift heavy ion irradiation. The nanopowders were well characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infra-Red (FTIR) spectroscopy. PXRD results confirm monoclinic phase upon calcination at 800 °C for 2 h. SEM micrographs indicate that the powder is highly porous and agglomerated. The TEM images show that the powder consists of spherical shaped particles of size ∼15–60 nm. The TL studies were carried out with 100 MeV Si 7+ ions in the fluence range 3×10 11 –3×10 13 ions cm −2 as well as with UV exposed in the range 1–70 min. It is observed that in UV exposed samples, the glow curve structure is simple and TL intensity increases up to 20 min UV dose and after that it decreases. The trap parameters were analyzed using glow curve deconvolution and peak shape method and results are discussed in detail.

Nd2O3:Co2+ (1–4 mol%) nanophosphors (15–25 nm) have been prepared via low temperature solution combustion method. Scanning electron micrograph (SEM) shows that the product is highly porous in nature. The stokes line in the Raman spectrum at ∼2000 cm−1 is assigned to Fg mode and the anti-stokes lines are assigned to a combination of Ag + Eg modes. With increase of Co2+ concentration, the intensity of Fg mode decreases, whereas the combination of Ag + Fg modes completely disappears. Electron paramagnetic resonance (EPR) spectrum exhibits two resonance signals with effective g values at g = 2.25 and g = 2.03. Thermoluminescence (TL) response of Nd2O3:Co2+ nanopowders with γ dose 0.23–2.05 kGy was studied. The activation energy (E) and frequency factor (s) are estimated using Chen's glow peak shape method and obtained to be in the range 0.45–1.67 eV and 1.8 × 104 to 4.0 × 1012 s−1, respectively. It is observed that the TL glow peak intensity at 430 K increases linearly with γ dose which is suitable for radiation dosimetry.

Red light emitting cubic Y1.95Eu0.05O3 nanophosphors have been synthesized by a low temperature solution combustion method using ethylene diamine tetra acetic acid (EDTA) as fuel. The systematic studies on the effect of calcination temperature on its structural, photoluminescence (PL), and thermoluminescence (TL) properties were reported. The crystallinity of the samples increases, and the strain is reduced with increasing calcination temperature. SEM micrographs reveal that samples lose their porous nature with an increase in calcination temperature. PL spectra show that the intensity of the red emission (611 nm) is highly dependent on the calcination temperature and is found to be 10 times higher when compared to as-formed samples. The optical band gap (E-g) was found to reduce with an increase of calcination temperature due to reduction of surface defects. The thermoluminescence (TL) intensity was found to be much enhanced in the 1000 degrees C calcined sample. The increase of PL and TL intensity with calcination temperature is attributed to the decrease of the nonradiative recombination probability, which occurs through the elimination of quenching defects. The trap parameters (E, b, s) were estimated from Chen's glow peak shape method and are discussed in detail for their possible usage in dosimetry.

CdSiO 3 :Co 2+ (1–7 mol %) nanophosphors have been prepared via solution combustion method with post calcination at 800 °C for 2 h for the first time. The formation of expected monoclinic phase was investigated by Powder X-ray diffraction (PXRD) measurements. The effect of different fluxes like NaF, NaCl, NH 4 F and NH 4 Cl on the crystallinity, phase and morphology of CdSiO 3 was investigated in detail. The crystallinity of the samples can be greatly enhanced by using fluxes rather than increasing the calcination temperature. Scanning electronic micrograph (SEM) image shows that the powder morphologies are highly influenced by flux addition. The addition of 2 wt% of fluxes would drastically enhance the crystallinity when NaCl, NH 4 F and NH 4 Cl fluxes are used. A well resolved single thermoluminescent glow peak at ∼170 °C was recorded for all the samples. Among all the halide fluxes, NaCl flux was found to be the potential one in enhancing the TL peak intensity along with crystallinity.

A series of Pr(3+) (1-9 mol%) doped CdSiO(3) nanophosphors have been prepared for the first time by a low temperature solution combustion method using oxalyldihydrizide (ODH) as a fuel. The final product was characterized by Powder X-ray diffraction (PXRD), Fourier Transform Infrared Spectroscopy (FTIR), scanning electron microscopy (SEM), and UV-Vis spectroscopy. The average crystallite size was calculated using Debye-Scherrer's formula and Williamson-Hall (W-H) plots and found to be in the range 31-37 nm. The optical energy band gap (E(g)) of undoped for Pr(3+) doped samples were estimated from Tauc relation which varies from 5.15-5.36 eV. Thermoluminescence (TL) properties of Pr(3+) doped CdSiO(3) nanophosphor has been investigated using γ-irradiation in the dose range 1-6 kGy at a heating rate of 5 °C s(-1). The phosphor shows a well resolved glow peak at ∼171 °C along with shouldered peak at 223 °C in the higher temperature side. It is observed that TL intensity increase with increase of Pr(3+) concentration. Further, the TL intensity at 171 °C is found to be increase linearly with increase in γ-dose which is highly useful in radiation dosimetry. The kinetic parameters such as activation energy (E), frequency factor (s) and order of kinetics was estimated by Luschiks method and the results are discussed.

YAlO(3):Cr(3+) (0.1 mol%) nanophosphor has been synthesized by low temperature solution combustion method. The X-ray diffraction studies reveal an orthorhombic structure. Transmission electron microscopy reveals that the particles are spherical in shape with nano-size ~40-65 nm. Electron paramagnetic resonance (EPR) spectrum shows a resonance signal with effective g value at g=1.978 which can be attributed to the exchange coupled Cr(3+) ion pairs in weakly distorted sites. The photoluminescence spectrum shows an intense doublet at 677 nm and 694 nm (R lines) assigned to spin-forbidden (2)E(g)→(4)A(2)(g) transition of Cr(3+) ions. EPR and PL studies reveal that the Cr(3+) ions occupy Al(3+) sites in YAlO(3). The interesting feature reported in this work concerns the linearity with gamma dose in the wide range (0.1-6 kGy). Prominent TL glow peaks at 226 °C and 346 °C were observed for both γ and UV-rays respectively. It is observed that the peaks at 226 °C and 346 °C eventually show a linear response up to 5 kGy which makes them a candidate for high dose dosimetry of ionizing radiation. The kinetic parameters namely activation energy (E), order of kinetics (b), frequency factor (s) of undoped and Cr doped samples were determined using Chens glow peak shape method and the results are discussed in detail.