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A series of carbon-doped solid solutions of ceria bismuth oxide (CBO) were prepared by a solid solution method. Highly porous solid solutions crystallized in a fluorite phase and C-doped samples exhibited an enhanced band-gap and reduced lattice cell constants. Their photocatalytic activity was observed in terms of H2 and O2 production via water splitting. The maximum hydrogen production was observed for a 6% C-doped solid solution in methanolic solution, i.e. 5413.10 mmol H2 g−1 h−1 under 300 W Xe light irradiation. The 6% C-doped solid solution released maximum O2 (193.80 μmol O2 h−1 g−1) and H2 (323.00 μmol H2 h−1 g−1) from pure water under exposure to real sunlight due to the highly ordered atomic arrangement, high porosity, high crystallinity, low oxygen vacancies, and high OH-group concentration in the lattice.

A series of quadruple perovskites Ca1+xCu3-xTi4O12 was scanned by different spectroscopic and microscopic techniques. X-ray powder diffraction pattern analysis revealed that the system transformed from a monophasic (x = 0.0, 0.1 and 0.2) to biphasic (x = 0.5 and 1.0) on Ca2+ - substitution. The completely different grain morphology and the distinct signature of the UV–visible absorption band and Raman scattering peak reflect this finding well. The defects arise mainly because of the mismatch between ion and site radii. The results of positron annihilation spectroscopy to study the nature of the defects are consistent with the proposed defect-rich sample history. There are many vacancies-type defects, whose size and concentration could be characterized through the measured positron lifetimes and coincidence Doppler broadening. The results show that for x = 0.1 itself, a secondary phase may be formed. The structure-property and property-property correlations are studied.

Polycrystalline ceramic sample of novel lead manganese silicate (Pb2Mn2Si2O9: Kentrolite) was prepared by solid state reaction at 860°C. Structural, morphological, dielectric and magnetic properties of the prepared product were investigated using XRD, EDS & SEM, impedance spectroscopic and VSM techniques. Rietveld refinement of XRD and EDS & SEM analysis confirmed that stoichiometric Pb2Mn2Si2O9 crystallizes in the orthorhombic structure (space group P21221, No.: 18). Frequency dependence of impedance and optical absorption studies establishes semiconducting nature of Pb2Mn2Si2O9. Dispersion in the dielectric parameters is observed due to hopping of electrons between Mn3+↔Mn2+ and Pb2+↔Pb3+. Pb2Mn2Si2O9 displays paramagnetic character at 300K and, it undergoes multiple magnetic transitions at TN = ~67K and TG = ~17K. This compound exhibits Curie-Weiss (θP) = −70K and the best fitted μeff = 3.76μB/Mn ion shows close agreement with the magnetic moment of free Mn3+ ion. Further, this study unveils co-existence of in plane ferromagnetic order (high coercivity = ~1000Oe and low retentivity = ~0.05emu/g) and long range antiferromagnetic order in Pb2Mn2Si2O9 at low temperatures.

In this study, Zn1-xLixO (x = 0.02, 0.04, 0.06, 0.08 and 0.10) nanohexagons were prepared by sol-gel combustion route and characterized using standard techniques for understanding their crystallography, surface morphology, optical, photoluminescence and magnetic properties. Single phase wurtzite type hexagonal crystal structure of the synthesized Li doped ZnO nanoparticles was identified from the Rietveld profile refinement of the powder XRD patterns and HRTEM & SAED analysis. HRTEM micrographs and XRD peak profile analysis confirmed formation of highly crystalline Li doped ZnO nanohexagons (ZnO:Li NHs) with average crystallite size in the 20–40nm range. Formation of functional Zn(Li)–O bonds in ZnO:Li NHs was confirmed by FTIR. SEM micrographs of the prepared samples showed random shaped, uniform distribution and well dispersed grains of ZnO:Li NHs. All the ZnO:Li NHs absorbs significant light in the UV band and the band gap energy monotonically decreases with increasing Li concentration in ZnO:Li NHs. Photoluminescence spectra exhibited two characteristic emission bands in all the ZnO:Li NHs and the UV emission band showed red shifting with increasing Li concentration, which is ascertained with the optical absorbance spectrums. Visible band spectral analysis of the PL data revealed formation of neutral, mono, and divalent oxygen vacancies along with the other defects like Zn vacancy in the ZnO lattice by Li doping and synthesis mechanism. All the ZnO:Li NHs exhibited weak ferromagnetism at RT. Lattice defects and oxygen vacancies created by Li1+ ions in the host ZnO lattice play significant role in band gap narrowing, photoluminescence in orange-red region and weak ferromagnetic ordering in ZnO:Li NHs.

The current research focuses on the photocatalytic, sonocatalytic and sonophotocatalytic degradation of nigrosine dye with nitrogen-doped and undoped zinc oxide powders. The sonophotocatalytic degradation of dye was found to occur at a higher rate than during photo- or sonocatalytic processes. Nitrogen-doped and undoped zinc oxide powders were synthesized by a wet chemical method. Further, scanning electron microscopy (FESEM), electron dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), UV-VIS spectroscopy (UV-VIS) and transmission electron microscopy (TEM) were used for the characterization of N-doped ZnO. The kinetics of nigrosine degradation were also studied and the results indicated that the degradation kinetics of nigrosine followed the first-order kinetics. The rate constant and the percentage of degradation were found to be highest, 7.33 × 10−4 (s−1) and 92% respectively, for sonophotocatalytic process after 90 min of reaction. Due to an increase in the available surface area or active sites of the catalyst, a higher rate constant and degradation efficiency was observed in the sonophotocatalytic system than in the photocatalysis system.

Nanoparticles of pure ZnO and monovalent, divalent & trivalent doped Zn0.96T0.04O (T: Li+, Ca2+& Gd3+) were prepared by the nitrate-citrate based sol-gel method. Powder XRD, TEM and photoluminescence data analysis confirmed single phase formation of pure ZnO, Zn0.96Li0.04O, Zn0.96Ca0.04O and Zn0.96Gd0.04O nanocrystals in the wurtzite type hexagonal lattice with surface and intrinsic crystal defects. UV–Vis–NIR optical absorption measurement demonstrated significant optical light absorption in the visible and UV bands for all the samples. A photo absorption peak below 380 nm is observed in all the four samples. The band gap energies were estimated to be 3.03eV, 2.78eV, 2.90eV and 2.79eV for ZnO, Zn0.96Li0.04O, Zn0.96Ca0.04O and Zn0.96Gd0.04O respectively. Monovalent and trivalent doping in ZnO induces reduction in the band gap energy and increment in the refractive index. 325 nm excited photoluminescence spectrums of pure and doped ZnO samples displayed a peak in the UV region and a broad peak in the visible band. Ca, Li and Gd doping in ZnO leads to red shifting of the UV emission band by substantial decrement in the band-gaps. Deconvoluted PL data analysis attests presence of various types of defects in the ZnO lattice which leads to strong electronic emission in the visible band. Computed values of CCT were found to be below 4000 K in these nanocrystalline samples, which makes them suitable material for the household optoelectronic devices. This study suggests that monovalent (Li+) doping in ZnO is better choice for tuning the optical and photoluminescence properties for their possible utilization in light harvesting and energy conversion applications.

This article describes synthesis of superparamagnetic fcc-CaFe2O4 nanoparticles by a metal nitrate-citrate monohydrate sol–gel route and characterization using X-ray diffractometry, Raman spectroscopic, UV–Vis–NIR optical absorption spectroscopic, Mossbauer spectroscopy, dielectric and SQUID magnetometry measurements. Rietveld refinement of the X-ray diffraction pattern and observation of active A1 g, T2 g & Eg modes in the Raman spectrum confirmed formation of single phase CaFe2O4 nanoparticles in the spinel ferrite type fcc structure without impurity. Mossbauer and Rietveld data analysis revealed that nanocrystalline CaFe2O4 is dominantly an inverse ferrite in which 85% Ca atoms preferentially occupy the octahedral site in the fcc symmetry and the Fe ions are in high spin Fe+3 state. Nanocrystalline CaFe2O4 significantly absorbs optical light below 500 nm and the direct band gap energy is estimated to ~1.83 eV, which is higher than 1.26 eV reported for orthorhombic CaFe2O4. Temperature and field dependent magnetic studies showed that fcc-CaFe2O4 nanoparticles exhibit superparamagnetism at room temperature with high saturation magnetization of 1.07μB. The blocking temperature is ~53 K at 1000 Oe and ~72 K at 500 Oe clearly shows lowering of blocking temperature at higher magnetic field. Interestingly below the blocking temperature at 20 K, CaFe2O4 nanoparticles behave as non collinear soft-ferrimagnetic material with a saturation magnetization of 1.16 μB, coercivity of 150 Oe and remanence of 4.45 emu/g. The magnetic momenta of Fe+3 ions residing at the octahedral sub-lattice are canted at ~25 °.

Impact of hydrogenation on the structural, dielectric and magnetic properties of half-doped La0.5Ca0.5MnO3 manganate have been investigated. Polycrystalline sample of La0.5Ca0.5MnO3 was prepared through solid state reaction at ~ 1300 °C. Subsequently, the prepared sample was annealed at 600 °C for 6 h in a continuous flow of hydrogen gas in a tubular reduction furnace. Single-phase orthorhombic structure of the hydrogenated La0.5Ca0.5MnO3 in the space group Pnma was confirmed by Rietveld refinement of PXRD and FTIR analysis. SEM micrographs revealed well resolved grains of ~ 2 μm in a good crystalline sample. Hydrogenated La0.5Ca0.5MnO3 showed a sharp optical absorption peak in the UV range with a bandgap energy of 4.96 eV. Hydrogenation of La0.5Ca0.5MnO3 leads to significant reduction in the magnitude of dielectric constant and tangent loss at room temperature. Paramagnetic character of La0.5Ca0.5MnO3 at 300 K is retained upon the hydrogenation but the low temperature magnetic properties get modified dramatically. Temperature and field dependent magnetization measurements showed that hydrogenated La0.5Ca0.5MnO3 undergoes paramagnetic to antiferromagnetic transition at TN = ~ 110 K and in a disordered magnetic phase below 50 K. Systematic enhancements in the magnitude of saturation magnetization (Ms), coercivity (Hc), remanence (Mr) and squareness ratio at 50 K and 20 K indicate for the coexistence of antiferromagnetic and weak ferromagnetic order due to competitive magnetic exchange interactions between Mn3+ and Mn4+ ions. This study shows that hydrogenation plays key role in the modification of dielectric and magnetic properties of La0.5Ca0.5MnO3.

This article presents an in-depth study on the structural, morphological, electrical and magnetic characterizations of two new phases of apatite-type lanthanide silicates. Polycrystalline samples of neodymium and samarium–manganese silicates (Nd4MnSi3O13 and Sm4MnSi3O13) were synthesized using a high-temperature solid-state reaction route. Rietveld profile refinement of X-ray diffraction data and FTIR analysis revealed that Nd4MnSi3O13 and Sm4MnSi3O13 crystallize in the single-phase apatite-type hexagonal structure with P63/m space group. Scanning electron micrographs showed good crystallinity in the two silicate samples, and the average size of the grains is found to be in submicrons. Frequency dependence of dielectric constant and tanδ for Nd4MnSi3O13 and Sm4MnSi3O13 showed systematic decrement with frequency. DC conductivity studies are indicative of low activation energy and semiconducting nature of Nd4MnSi3O13 and Sm4MnSi3O13. At room temperature, both the silicates exhibit dominant paramagnetism; however, short-range one-dimensional ferromagnetic chains coexist in the paramagnetic state of Nd4MnSi3O13 and Sm4MnSi3O13.

The electronic structures of stoichiometric, single phase, coarse-grained CaCu3-xTi4-xFe2xO12 (x = 0.0, 0.1, 0.3, 0.5 and 0.7) polycrystalline ceramics have been investigated using powerful X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopic measurements, performed near Ti L3,2 and Ti K- edges, registered at 300 K. The absence of pre-edge structures in Ti L3,2 – edge are indicative of a departure from octahedral cubic symmetry, while the observed small increase in the intensity of absorption peaks has been attributed to increasing spin-orbital coupling with increasing Fe-content (x) in the system. The presence of a pre-edge feature in Ti K- edge spectra confirms the presence of octahedrally coordinated Ti4+ ions in the system. The EXAFS spectra measured at Ti K- edge indicate the first shell Ti—O bond distances to be nearly 1.56 A in the sample without Fe. With the increase in the Fe- concentration (x), the Ti-O distance shows a slight reduction. The second shell Ti-Ca bond distance comes out to be nearly 2.6 A which decreases with an increase in the Fe - concentration.

In this study, the correlation between the concentration of dopant ions and oxygen vacancy defect of Sm-doped CeO2 Nano-particles (NPs) were investigated systematically by X-ray diffraction (XRD), Ultraviolet–visible-Near Infrared spectroscopy (UV–Vis–NIR) and Surface-enhanced Raman spectroscopy (SERS). The nano-crystalline C e 1 − x S m x O 2 (x = 0.00, 0.02, 0.04, 0.06, 0.08 and 0.10) samples were synthesized using co-precipitation chemical route. The XRD measurements revealed that Sm3+ ions are successfully incorporated at the Ce4+ ion sites in the face centered cubic (fcc) lattice of CeO2 NPs. The high-resolution transmission electron microscopy (HRTEM) and Selected area electron diffraction (SEAD) patterns were analyzed to study the surface morphology, crystallinity, atomic structure of the samples. The average particle size calculated with TEM images was obtained in the range of 5–8 nm for C e 1 − x S m x O 2 samples for all the doping concentrations. The UV–Vis–NIR spectroscopy and Surface-enhanced Raman Spectroscopy were analyzed to investigate the optical properties and defect structure in these NPs. The UV–Vis–NIR spectroscopy measurements revealed that due to aggregation of particles the optical band gap energy was varied with fluencies of Sm3+ ions as well as due to particle size variations of NPs. Peak asymmetry and broadening of Raman active mode further ascribed the presence of oxygen vacancy (whether extrinsic or intrinsic), which were varied with the fluencies of Sm3+ ions in CeO2 NPs. This paper presented a systematic study on the fluencies of Sm doping in CeO2 nano-particle lattice to understand the role of vacancies, intrinsic and extrinsic oxygen vacancies and their effect on tailoring the structural and optical properties of doped CeO2 nano-particles for various applications like luminescent materials, oxygen transportation, catalysts, ultraviolet fuel cells, corrosion prevention etc.

We report, the effect of heat treatments slow cooling, rapid thermal cooling (quenching) and microwave-assisted heating, on structural, microstructural and J – E characteristics of CaCu3Ti4O12 polycrystalline ceramic. Rietveld refinement of X-ray data confirms the emergence of the mono-phasic cubic perovskite structure, diffraction line broadening and change in the relative intensity of diffraction peaks while scanning electron microscopy revealed completely different grain morphology. The observed modifications have been discussed in detail. The strong nonlinear J – E characteristics over the wide temperature range (300–823 K) indicated the existence of a Schottky-type electrostatic potential barrier at the grain boundaries. The parameters, nonlinear coefficient, threshold electric field, potential barrier height suggest suitability of the materials for low voltage varistor applications.

The present study reports the effect of Fe-doping on the structural, optical, magnetic and electronic properties of polycrystalline CeO2 (for 5 and 10% doping concentration of Fe-cation) samples synthesized by low-temperature solid-state reaction method. Rietveld refinement of the X-ray diffraction patterns establishes fluorite-type face-centred cubic structure of the Fe-doped CeO2 samples and also confirms successful incorporation of Fe ions in the CeO2 lattice. The UV–Vis–NIR absorption spectra displays reduce band gap energy with rising fluency of Fe-ions, which confirm red shifts in the Fe-doped CeO2 samples. The electronic structure of the pure CeO2 and Fe-doped CeO2 polycrystalline samples have been investigated by X-ray photoemission spectroscopy (XPS). The XPS spectra of Ce 3d reveals the reduction of Ce4+ to Ce3+ states Fe-doped CeO2 samples, which are well supported by the Fe 2p and O 1s spectra. Pure polycrystalline CeO2 displays diamagnetic behaviour at room temperature. Interestingly, 5% Fe-doped CeO2 sample displays S-shape hysteresis loop and establishes room temperature ferromagnetism, whereas, 10% Fe-doped CeO2 sample shows weak ferromagnetic behaviour. A decrement is observed in the magnetization on increasing the doping concentration. The possible reason for ferromagnetism in the Fe-doped CeO2 samples may be incorporation of oxygen vacancies, which are further discussed using F-centre exchange mechanism and double exchange interaction. These experimental findings offer potential opportunities for spintronics and optoelectronics applications by integrating them into device structures and evaluating their performance as a function of their material properties.

Understanding of origin of ferromagnetism in dilute magnetic oxides (DMO's) has become one of the most challenging research problems in condensed matter physics. Here we are reporting a detailed study of magnetic properties and electronic structure of two 5% Co-doped ZnO samples (the as-prepared sample Zn0.95Co0.05O and the hydrogenated sample Zn0.95Co0.05O:H). The as-prepared sample is found to be paramagnetic while through hydrogenation, we observed inducement of remarkable ferromagnetism in it. The H-mediated magnetic transition is accompanied by electronic structure modifications with no structural deviations. To get in-depth information into electronic structure correlations of the observed ferromagnetism, we have investigated their electronic properties in detail. For this purpose, we have employed the site-selective and element-sensitive X-ray-absorption spectroscopy (XAS) in the vicinity of the Cobalt L2,3 edge, the oxygen K edge, and the Zinc L3 edge using synchrotron radiation. The Co L2,3 edge spectra clearly show that Co dopants reside at the Zn sites for both these samples and that they are tetrahedrally coordinated with the ligand O atoms. Very minor changes are observed in the Zn L3 edge spectra. However, the O 1s edge spectra display dominant additional components in the ferromagnetic hydrogenated sample Zn0.95Co0.05O:H, not observed in the as-prepared non-magnetic sample Zn0.95Co0.05O. We conclude that the observed spectral features can be attributed to the presence of O vacancies and the hybridization of Co 3d states with O 2p vacancy states. These two factors together are likely to play important role in inducement of ferromagnetic ordering in this Co-doped ZnO system. However, which of these two weighs more in this mechanism, cannot be pinpointed and more studies are required in this regard.

This work is aimed to understand magnetic behavior at low temperature of nano particles of Zn0.5Co0.5Fe2O4 ferrite. The sample has been synthesized by using a Sol Gel method. Rietveld refinement of XRD data confirms the single-phase cubic spinel crystal structure with lattice constant a = 8.41 A. The average crystallite size ~30 nm has been determined by Debye-Sherer formula. The field emission scanning electron microscopy micrographs show the spherical nature of nanoparticles and energy dispersive X-ray measurement confirms the elemental composition in the sample. Also, the Mapping of the sample has been performed which shows the appropriate distribution of elements in the sample. Magnetic measurements have also been performed in variable applied magnetic field (up to 5 T) and temperature (up to 2 K). The zero field cooled, field cooled curves have been measured under the applied magnetic field 50, 100 and 500Oe. The competition between thermal and magnetic energy has been studied in detail. In addition, the M-H loop has been measured at different temperatures i.e. 300 K, 200 K, 120 K, 100 K, 50 K and 5 K, by applying a variable external magnetic field up to ±5 T. The M-H loop is observed continuously decreasing with increasing temperature. The Bloch’s law fitted in the saturation magnetization which gives Mo = 113.045emu/gm, T0 = 547.45 K and α B = 1.5. Also, the Kneller’s law fitted in variable coercivity with respect to temperature which suggests that the blocking temperature ~360 K (i.e. above the room temperature). Furthermore, the dM/dH peak height is increasing with increasing temperature which indicates the good magnetic state of the sample.

Polycrystalline sample of novel Cobalt-akermanite: Ca2CoSi2O7 was synthesized using solid state reaction method. Room temperature powder X-ray diffraction and dc-electrical conductivity studies confirmed good quality of the synthesized sample in single phase tetragonal structure with space group: P 4 21m. Low value of activation energy estimated from the dc-conductivity study indicates insulating behavior of this compound. Magnetic study showed a paramagnetic nature of Ca2CoSi2O7 at room temperature and antiferromagnetic nature below TN=5.6 K. In this compound weak ferromagnetism co-exist with antiferromagnetism below Neel temperature. Ca2CoSi2O7 displays magnetic field induced weak ferromagnetic transition around 7.4 K. Antiferromagnetic interactions occurs between the nearest neighbor Co2+ ions, as indicated by the negative sign of Weiss constant, θP=−22.7 K. Estimated value of the effective magnetic moment, μeff=4.75μB is found to be larger than the spin-only value of magnetic moment of Co2+ ion in the tetrahedral coordination having three unpaired electrons. These results, suggest that the orbital contribution to magnetic moment in this compound cannot be neglected and the electric polarization through spin dependent p-d hybridization can be expected in Ca2CoSi2O7.

We report here the impact of Gd substitution on structural, optical, photoluminescence and magnetic properties of Zn1−xGdxO (x = 0.02–0.10) nanocrystals. Rietveld refinement of PXRD patterns, SAED and FTIR analysis revealed that Zn1−xGdxO nanoparticles crystallize in single phase wurtzite type hexagonal symmetry. HRTEM & SEM analysis confirmed good crystallinity of Zn1−xGdxO nanocrystals with a wide size distribution in 10–40 nm range. Concentration of Gd3+ ions at the Zn site causes a systematic reduction in the average crystallite size of Zn1−xGdxO nanocrystals. UV-Vis-NIR and photoluminescence spectroscopic studies showed decrement in band gap energy and suppression of UV emission (391–416 nm) with Gd concentration in Zn1−xGdxO. Analysis of the visible band emission spectra demonstrated that 325 nm photoexcited Zn1−xGdxO nanocrystals emit light in the orange-red region due to formation of complex defects in the ZnO lattice. M-H curves of 2% and 4% Gd doped ZnO nanocrystals recorded at 300 K showed thin ferromagnetic hysteresis loop (almost equal Mr =~1.8 memu/g and Hc=~210 & ~136 Oe for 2% and 4% Gd doped ZnO respectively) at lower magnetic fields but in the high field range, the magnetization responded linearly with the applied magnetic fields and, thus establishes coexistence of paramagnetic and weak ferromagnetic ordering in 2% and 4% Gd substituted ZnO nanocrystals. The higher 6%, 8% and 10% Gd substituted ZnO nanocrystals are found to be paramagnetic at 300 K. At 5 K, all the samples showed S-shaped M-H curves with negligible coercivity & retentivity and the magnetization monotonically incremented (5–25 emu/g) with increasing Gd concentration in Zn1-xGdxO. Superparamagnetic clusters and antiferromagnetic states coexist in Zn1−xGdxO nanocrystals at 5 K. Magnetic and optical properties of Zn1−xGdxO nanocrystals are suitable for magneto-optoelectronic applications.

In the present work, photo-Fenton degradation of Sunset Yellow FCF under visible light was carried out by using copper loaded bentonite and hydrogen peroxide. The photocatalyst was prepared by loading copper ions on bentonite by wet impregnation method. The rate of photocatalytic degradation of dye was measured spectrophotometrically by measuring absorbance of the reaction mixture at regular time intervals. The effect of various parameters such as pH, concentration of dye, amount of photocatalyst, amount of H 2 O 2 and light intensity on the reaction rate has also been studied. Characterization of photocatalyst has been done by IR spectroscopy, scanning electron microscopy and X-ray diffraction. The Chemical Oxygen Demand (COD) of the reaction mixture has been determined before and after treatment. A tentative mechanism involving OH radical as an oxidant for degradation of dye has also been proposed. Involvement of OH radicals as an active oxidizing agent has been confirmed by using isopropanol and butylated hydroxy toluene (BHT) as radical scavengers. It has been observed that the rate of reaction is drastically reduced in the presence of these scavengers. The rate of reaction is much retarded by using BHT as compared with isopropanol.

Inspired by the ancient art work and recent scientific advances in inorganic blue pigments, we have synthesized polycrystalline ceramic samples of barium copper tetrasilicate (BaCuSi4O10) and strontium copper tetrasilicate (SrCuSi4O10) using solid state reaction route to understand their crystallography, magnetism and optical behaviour. Powder X-ray diffraction patterns confirmed single phase tetragonal crystal structure with space group P4/ncc for both the pigment samples. The unit cell lattice parameters and other structural parameters of these samples were determined using the Rietveld profile refinements of powder diffractograms. Both of these blue pigments show swift optical absorption below 300 nm and considerable absorption in the visible and infrared regions. The obtained values of band gap for BaCuSi4O10 and SrCuSi4O10 were found to be 3.61 and 3.52 eV respectively. Temperature and field dependent magnetization measurements are suggestive of paramagnetic state at room temperature and superparamagnetic state at low temperatures in both these compounds. The estimated values of effective magnetic moments were found to be 1.833 and 1.91 μB for BaCuSi4O10 and SrCuSi4O10 respectively. Interestingly these obtained values of magnetic moments are very close to the theoretical value of 1.73 μB for Cu2+ ion.

In this paper, we report on the influence of Li doping on the structural, morphological, electrical, optical and magnetic properties of Zn0.96−xMn0.04LixO (for x = 0.02, 0.03, 0.04) nanocrystals synthesized by a simple low-temperature co-precipitation method. Rietveld refinement of the XRD patterns confirmed single phase Wurtzite type hexagonal structure of the nanoparticles and expansion in the lattice cell volume with increasing content of Li. TEM images reveal formation of hexagon shaped nano-crystals and also show a good agreement with the crystallite size estimated from the XRD analysis. The I–V characteristics show that resistivity of the samples decreases with increasing Li concentration. The UV–Vis-NIR absorption studies show a reduction in optical energy band gap than that reported for pure ZnO which decreases gradually with increasing Li concentration, showing a qualitative agreement with the I-V characteristic results. Magnetization measurements show clear evidence of weak ferromagnetic ordering at room temperature, which increases with Li content. The observed ferromagnetism seems to show close correlation with the oxygen vacancy defects induced by Li doping.

This article reports on the oxygen vacancies and defects induced cooperative magnetism of 28nm (as prepared) and 74nm (annealed) sized nanocrystals of ZnO synthesized through sol- gel auto-combustion route. UV–Vis–NIR optical absorption and photoluminescence (PL) spectroscopic measurements showed marginal red shifting in the band gap energy and characteristic blue shift in the UV absorption peak position with the size reduction of ZnO nanocrystallites. PL analysis revealed that 28nm sized ZnO nanocrystals have higher number of oxygen vacancies and lower interstitial defects in comparison to 74nm (annealed) nanocrystals of ZnO. Both the sample display oxygen vacancy and defect mediated ferromagnetic behaviour at 300K but 28nm ZnO nanocrystals are better ferromagnetic in comparison to annealed ZnO nanocrystals. The annealed ZnO nanocrystals also showed considerable diamagnetic character. High field (±7 Tesla) magnetization measurements down to 5K and PL analysis establish presence, inter-conversion of oxygen vacancies and valence fluctuations in neutral, mono and divalent oxygen vacancies. The monovalent oxygen and zinc vacancies play important role in the mediation of d0 type cooperative magnetism in the ZnO nanocrystals.

We have investigated ferromagnetic and optical properties, local geometrical structure for Ce1-xPrxO2 (x = 0, 2, 4, 6 and 8% Pr doping) co-precipitation method-synthesized nanomaterials, which were hydrogenated subsequently. Dopant ion concentration, its valence state and effect of hydrogen annealing are correlated with oxygen vacancies and their role in magnetism is discussed with X-Ray diffraction, Raman spectroscopy and Magnetic measurements. The results support the fluorite structure formation for Pr-doped CeO2 nanomaterials without any impurity phase. Red shifting of band gap energy with increased Pr concentration can be seen in the absorption spectra. Raman active modes at ∼500-650 cm−1 confirm the formation of oxygen vacancies, varying with Pr4+/Pr3+ ions in the CeO2 lattice. A sharp peak at ∼3611 cm−1 in FTIR spectra broadens on interaction with H, due to combination of Hydrogen with adjacent Oxygen forming OH moiety within the CeO2 lattice. The magnetization results performed at room temperature confirm ferromagnetic signal for all the samples, with enhanced/reduced FM ordering for different Pr doping fluencies, explained by F-Centre exchange Mechanism with the formation of various complexes, Ce4+-Vo-Ce3+, Pr4+-Vo-Ce3+, or Pr3+ -Vo-Ce3+ in the CeO2 lattice. These nanomaterials are suitable for various applications e.g. Solid state electrolyte for fuel cells, UV blockers, photo-catalyst, magneto-optic devices and primarily for spintronics applications.

The CeO2-δ and Ce1-xNdxO2-δ (x = 0.02, 0.04 and 0.06) nanoparticles, synthesized by microwave assisted co-precipitation method have been investigated for structural, optical, electronic structure and magnetic properties using X-ray diffraction, transmission electron microscopy, Absorption spectroscopy, surface enhanced Raman spectroscopy, X-ray absorption spectroscopy (XAS), and SQUID magnetometer. TEM and XRD measurements indicate face-centred cubic fluorite structure of CeO2 with Fm-3m space group. The Raman spectroscopy indicates that all the Nd3+-doped CeO2 samples downward shifting of F2g band with introduction of oxygen vacancies. Further, band gap decrement has been observed with incorporation of Nd3+ ions in CeO2 lattice. The XAS spectra of Ce M − edge clearly indicate changed valence state of Ce ions from Ce4+ to Ce3+ with Nd3+ doping concentrations. The formation of oxygen vacancies is also confirmed with O K- and Nd M-edges XAS analysis. It is revealed that new complexes Ce3+-VO- Nd3+ and Ce4+- VO –Ce3+ have been introduced to support FM ordering through the development of F+-centres. Therefore, it can be concluded that oxygen vacancies play a prominent role in improving the ferromagnetic and various properties of these nanomaterials, to make them suitable for many applications as UV blocker, Photocatalyst, Spintronics and Optoelectronics applications.

The structural, optical and electronic structure properties of all the Zn1-xCoxO nanoparticles [x = 0.01, 0.03, and 0.05], synthesized using co-precipitation method have been studied using X-ray diffraction (XRD), Surface Enhanced Raman Spectroscopy (SERS), UV–Vis–NIR spectroscopy and X-ray Absorption Spectroscopy measurements. The XRD and SERS analysis have confirmed the formation of hexagonal wurtzite structure (space group C46v). UV–Vis–NIR spectra indicate the blue shifting of the absorbance edge and the band gap is found to decrease with doping. The electronic structure of undoped and Co-doped ZnO nanoparticles have been investigated using site selective and element sensitive X-ray absorption spectroscopy. From the XAS spectra at Zn L3,2, Co L3,2 and O K-edges we have found that Zn ions are in +2 valence state in undoped and Co-doped ZnO nanoparticles. From the XAS analysis it can be seen that proper incorporation of Co-ion in the host lattice take place in t2geg state Co+2 (d7) under tetrahedral symmetry and maintain the crystal symmetry with lattice distortion. The Co-ion doping in the ZnO nano-matrix leads to creation of various defects & oxygen vacancies, which results in the blue shift in band-gap energy makes them useful for various applications e.g. photocatalytic water splitting, hydrogen generation, spintronics and optoelectronics.

In this paper, the irreversible magnetic behavior of Ni0.5Co0.5Fe2O4 nano-ferrite has been discussed with varying the temperature. The nano-ferrite discussed in present work synthesized using sol gel technique. The formation of the phase of Ni0.5Co0.5Fe2O4 was confirmed using X-ray diffraction (XRD), and their Rietveld refinement shows it crystallized into cubic structure with lattice constant 8.3541 A under space group Fd 3 - m . The homogeneity and the morphology of the sample was analysed using FESEM along with EDAX measurement. The irreversibility of Ni0.5Co0.5Fe2O4 was studied in three modes ZFCW, FCC and FCW using field dependent magnetic measurements in temperature range of 2 K–300 K under the presence of 50 Oe. However, the magnetic hysteresis of sample was studied at different temperature T = 5 K, 50 K, 100 K, 120 K, 200 K, 300 K from varying the field upto ±5 Tesla. Further, the asymmetry observed in the magnetization and demagnetization curve gives the value of H m , which increased with lowering the temperature due to magnetic crystalline phase as well as the micro-strain of the sample. Finally, retentivity, coercivity and saturation magnetization of the present sample makes it a potential candidate for magnetic memory devices, magnetic resonance imaging, medical diagnosis applications.

This study explore the influence of 10% Li doping on the crystallography, cation distribution, morphology, optical and magnetic properties of middle range Cobalt–Zinc nanoferrites. Single-phase intrinsic quaternary Co0.4+xZn0.6-xFe2O4 (x = 0.0, 0.1 and 0.2) and 10% Li doped quinary Co0.4+xZn0.5-xLi0.1Fe2O4 (x = 0.0, 0.05 and 0.1) nanoferrites with average crystallite size in the 13–34 nm range were synthesized through sol-gel auto-combustion method. Rietveld profile refinement of the PXRD patterns, presence of fcc rings in the SAED patterns and observation of active Raman modes illustrated single phase formation of mixed spinel nanoferrites in the fcc structure without impurity. In these nanoferrites Zn2+ ions preferentially occupy the tetrahedral site and Co2+ & Li1+ ions occupy the octahedral site with total preference. Both intrinsic quaternary and Li doped quinary nanoferrites significantly absorbs optical light in the UV band. The band gap energy decreases with decreasing Zn concentration and Li doping in these nanoferrite leads to blue shift of more than 1eV in the band gap energy. Co0.4+xZn0.6-xFe2O4 (x = 0.1 and 0.2) and Co0.4+xZn0.5-xLi0.1Fe2O4 (x = 0.0, 0.05 and 0.1) nanoferrites exhibited S-shape ferrimagnetic hysteresis loops at 300 K, 200 K, 100 K & 20 K. The Co0.4Zn0.6Fe2O4 nanoferrite display superparamagnetism at 300 K with a blocking temperature at 183 K. Systematic enhancement in the saturation magnetization (Ms), coercivity (Hc), remanence (Mr) and squareness ratio with lowering the temperature in these nanoferrites revealed conversion of soft-ferrimagnetic to hard-ferrimagnetic character. 10% Li doping in these nanoferrites resulted in significant enhancements of the Hc, Mr and TB. Monotonic increase in the Ms, Hc, Mr and TB has also been observed with the decreasing Zn concentration in these nanoferrites. Rich magneto-optical properties of quinary Co0.4+xZn0.5-xLi0.1Fe2O4 (x = 0.0, 0.05 and 0.1) nanoferrites can find applications in the design and fabrication of magneto-optic and permanent magnet based devices.

Thin film deposition process invariably introduces compressive or tensile stress in the films. The stress in a film causes the wafer to warp whose curvature is estimated in a wafer fab using optical reflectance technique. Alternatively, the wafer curvature can also be measured using the high resolution XRD (HRXRD) Si(004) rocking curves. In this paper, the HRXRD technique was employed to evaluate the stress in PECVD and HDP SiN films deposited on blanket Si wafers (prime-grade material) which were subjected to different Xe ion-implant energy conditions. It will be shown that stress-matching in PECVD and HDP SiN can be achieved by tuning Xe implant energy. From the change in the width of Si(004) peak, a qualitative assessment regarding the quality of single crystal Si lattice will be presented which is not possible to measure with optical reflectance methods.

Ca1+xCu3-xTi4O12, x = 0.0, 0.1, 0.2, quadruple perovskite system has been investigated by means of energy dispersive analysis of X-rays, powder X-ray diffractometry, scanning electron microscopy, dc magnetization in zero-field and field-cooled modes (M(T) curves) and isothermal magnetization against magnetic field (M(H) loop) plots. The stoichiometric samples possess a single-phase crystal structure and coarse-grained microstructure. The cation distributions reveal that substituted Ca2+ ions have a strong preference for Aʹʹ - site. The M(T) curves of pristine composition exhibit reversible thermomagnetic characteristic with classic antiferromagnetic transition at TN ~ 25 K. On Ca2+ substitution, the compositions (x = 0.1 and 0.2) show coexistence of weak ferromagnetism and antiferromagnetism for T