Magnetic and Electrical Properties of Ordered 112-type Perovskite LnBaCoMnO5+\delta (Ln = Nd, Eu)

Investigation of the oxygen-deficient 112-type ordered oxides of the type LnBaCoMnO5+\delta (Ln = Nd, Eu) evidences certain unusual magnetic behavior at low temperatures, compared to the LnBaCo2O5+\delta cobaltites. One observes that the substitution of manganese for cobalt suppresses the ferromagnetic state and induces strong antiferromagnetic interactions. Importantly, NdBaCoMnO5.9 depicts a clear paramagnetic to antiferromagnetic type transition around 220 K, whereas for EuBaCoMnO5.7 one observes an unusual magnetic behavior below 177 K which consists of ferromagnetic regions embedded in an antiferromagnetic matrix. The existence of two sorts of crystallographic sites for Co/Mn and their mixed valence states favor the ferromagnetic interaction whereas antiferromagnetism originates from the Co3+-O-Co3+ and Mn4+-O-Mn4+ interactions. Unlike the parent compounds, the present Mn-substituted phases do not exhibit prominent magnetoresistance effects in the temperature range 75-400K.Comment: 23 pages including figure

A comparative study of the electron- and hole-doped compositions of single crystalline Nd1−xCaxMno3Nd_{1-x}Ca_{x}Mno_{3} (x = 0.6 and 0.4) by Brillouin scattering

In order to understand the differences between the nature of the electron- and the hole-doped compositions of rare earth manganates, properties of single crystals of $Nd_{1-x}Ca_{x}MnO_{3}$ with x = 0.6 and 0.4 have been investigated. In the electrical resistivity measurements, the electron-doped (x = 0.6) composition shows no effect of magnetic field unlike the hole-doped (x = 0.4) composition, but both exhibit similar current-induced changes. Brillouin scattering studies show that the x = 0.6 and 0.4 compositions show softening of the modes on cooling the samples towards charge-ordering transitions. The strength of coupling between the $e_{g}$ orbitals and the elastic strain is considerably larger in the hole-doped composition containing a larger population of $Mn^{3+}$ ions

Temperature-dependent Brillouin scattering studies of surface acoustic modes in Nd0.5Sr0.5MnO3

Brillouin scattering experiments are carried out to study the surface acoustic waves in Nd0.5Sr0.5MnO3 as a function of temperature in the range of 40–300 K covering the metal-insulator and charge-ordering phase transitions. The surface modes include surface Rayleigh wave, pseudo-surface acoustic wave (PSAW) and high velocity PSAW. The observed softening of the sound velocities for the surface modes below paramagnetic to ferromagnetic transition, Tc is related to the softening of the C44 elastic constant. The subsequent hardening of the sound velocity below the charge ordering transition temperature Tco is attributed to the coupling of the acoustic phonon to the charge ordered state via long range ordering of the strong Jahn–Teller (JT) distortion

Synthesis, structure, CO oxidation, and H2 production activities of CaCu3−xMnxTi4−xMnxO12 (x = 0, 0.5, and 1.0).

Synthesis of nanocrystalline pristine and Mn-doped calcium copper titanate quadruple perovskites, CaCu3−xMnxTi4−xMnxO12 (x = 0, 0.5, and 1.0) by modified citrate solution combustion method has been reported. Powder X-ray diffraction patterns attest the phase purity of the perovskite materials. Average particle sizes of all the materials obtained from the Scherrer's formula are in the range of 55–70 nm. The specific surface areas for all the perovskites obtained from BET isotherms are found to be low as expected for the condensed oxide systems and fall in the range of 13–17 m2 g−1. Transmission electron microscopy studies show a reduction in particle size of CaCu3Ti4O12 with increase in Mn doping. Ca and Ti are present in +2 and +4 oxidation states in all the materials as demonstrated by X-ray photoelectron spectroscopy analyses. Cu2+ gets reduced in CaCu3Ti4O12 with higher Mn content. Mn is observed to be present only in +3 oxidation state. All the materials have been examined to be active in CO oxidation as well as H2 production from methanol steam reforming. CaCu3Ti4O12 with ~14 at.% Mn is found to show best catalytic activities among these materials. A comprehensive analysis of the catalytic activities of these perovskites toward CO oxidation and H2 production from MSR reveal the cooperative activity of copper-manganese in the doped perovskites and it is more effective at lower manganese content

InN Nanocrystals, Nanowires, and Nanotubes

Indium nitride has attracted increasing attention in the last few years because of its properties of potential value in optoelectronic devices and other technologies

Facile synthesis of CuCr2O4/CeO2 nanocomposite: A new Fenton like catalyst with domestic LED light assisted improved photocatalytic activity for the degradation of RhB, MB and MO dyes

Here, we report the findings on CuCr2O4/CeO2 (CCO/CeO2) nanocomposite as a new heterogeneous Fenton like catalyst for the degradation of rhodamine B (RhB), methylene blue (MB) and methyl orange (MO) under domestic LED light irradiation. An extensive characterization of the samples were performed using several physicochemical techniques. A careful monitoring of photo-activities reveals the best performance of 10%CCO/CeO2 showing complete degradation of 10 ppm RhB, MB and MO dyes within 15, 20 and 30 min, respectively, in presence of 4 mM of H2O2. The visible light absorption of CeO2 is enhanced by CCO. The radical trapping and coumarin fluorescence probe methods suggest the generation of radical dotOH in the catalytic pathways. A comprehensive analysis of radical dotOH generation in presence and in absence of LED irradiation is presented to underscore both the Fenton like reactions of the nanocomposite system. Importantly, the nanocomposite catalyst shows encouraging recycling behavior through an intermediate heat treatment. The Fenton like catalytic behavior of marginally active CeO2 is dramatically enhanced in presence of CCO in the nanocomposite due to larger creation of oxygen vacancy. Finally, a plausible explanation of this novel catalytic behavior based on band bending across the junction of the two semiconducting oxides has been presented

Anatase TiO2 decorated CuCr2O4 nanocomposite: A versatile photocatalyst under domestic LED light irradiation

The rutile and anatase polymorphs of TiO2 are the most extensively studied photocatalyst materials with the efficient absorption in the violet to near ultra violet region of the electromagnetic spectrum, which boost tremendous research endeavors in increasing the photocatalytic activity of TiO2 under visible light sources through rational modifications. Here, we report the astonishing performance of CuCr2O4(CCO)/anatase-TiO2 nanocomposite as a Fenton like catalyst with potential impact for sustainable design and environmental protection. All the materials were thoroughly characterized by several physico chemical techniques. CCO/TiO2 nanocomposite obtained by heat-treatment at 400 °C is found to exhibit high performance towards degradation of azo dyes like methylene blue (MB), rhodamine B (RhB) and methyl orange (MO), antibiotics like tetracycline hydrochloride and norfloxacine, and a promising Pt-free candidate for photoelectrocatalytic oxygen evolution reaction under domestic light emitting diode (LED) light irradiation. CCO/TiO2 shows high recycling activity and chemical stability. Under domestic visible LED light irradiation, the electrons are photoexcited from the conduction band of CCO to that of TiO2 resulting in enhanced charge separation eventually facilitating the catalytic performance of the nanocomposite. TiO2 plays two primordial roles, firstly, it acts as an electron receiver to improve the charge separation in the nanocomposite and secondly, it participates in the Fenton like reaction

Citrate combustion synthesized Al-doped CaCu3Ti4O12 quadruple perovskite: synthesis, characterization and multifunctional properties

The facile synthesis of the Al-doped CaCu3Ti4O12 quadruple perovskite, a well-known and vastly studied material for various technological applications, using the modified citrate combustion route along with structural, microstructural, and X-ray photoelectron spectroscopic (XPS) characterization and magnetic, dielectric and electrical properties has been investigated and reported here. The possible applications of the material as a Schottky barrier diode (SBD) in optoelectronic devices and as a catalyst in methanol steam reforming (MSR) reaction for hydrogen generation, hitherto unreported in the open literature, have also been explored. The compound is crystallized in the cubic body centered Im[3 with combining macron] space group and the particle size is found to be in nanodimension with rather narrow size distribution. The enhanced resistivity could be attributed to the grain boundary effect, and consequently, it exhibits better performance as a SBD compared to the undoped sample. Desired cationic composition with expected valence states within the probe range is confirmed by XPS analysis. A better catalytic activity towards MSR is noticed for the Al-doped CaCu3Ti4O12 compared to the undoped composition. These new findings, namely MSR activity and applicability in the Schottky device, have highlighted further the multifunctional nature of the material in energy related issues and would thus be of interest to the materials community searching for functional materials

Facile synthesis of CuCr2O4/BiOBr nanocomposite and its photocatalytic activity towards RhB and tetracycline hydrochloride degradation under household visible LED light irradiation.

Here we report the development of CuCr2O4/BiOBr nanocomposite photocatalysts for the first time to serve the purpose of rhodamine B (RhB) and tetracycline hydrochloride (TC-HCl) degradation using household visible light emitting diode (LED) light. In this nanocomposite, sol-gel combustion made spherical shaped CuCr2O4 nanoparticles are decorated on BiOBr plates in single pot via precipitation method using cetyltrimethylammonium bromide (CTAB) as the Br source as well as the template. The present investigation highlights a significant advancement to tackle the challenge of visible light induced photocatalytic degradation of harmful organic dye RhB and antibiotic-pollutant TC-HCl. The 20%CuCr2O4/BiOBr nanocomposite exhibits high degradation activity for both RhB (96.0% in 15 min) and TC-HCl (96.7% in 300 min) in presence of LED light with good recycling characteristics. Detailed structural and optical characterization using XRD, BET, FESEM, TEM, HRTEM, EDX, XPS, UV−Vis DRS, PL spectroscopy and Raman spectroscopy have been carried out prior performing photocatalytic activity tests. The structural as well as optical data have revealed a significant improvement in visible light absorption of BiOBr in presence of CuCr2O4. Based on energy band modification at the heterojunction of nanocomposite materials and their radical trapping ability, a plausible mechanistic path of photocatalytic degradation is presented