Effect of crystal structure and cationic order on phonon modes across ferroelectric phase transformation in Pb(Fe0.5-xScxNb0.5)O3 bulk ceramics

Pb(Fe0.5-xScxNb0.5)O3 [(PFSN) (0 ≤ x ≤ 0.5)] multiferroic relaxors were synthesized and the temperature dependence of phonon modes across ferroelectric to paraelectric transition was studied. With varying Sc content from x = 0 to 0.25 the structure remains monoclinic and with further addition (x = 0.3 - 0.5) the structure transforms into rhombohedral symmetry. Structural refinement studies showed that the change in crystal structure from monoclinic to rhombohedral symmetry involves a volume increment of 34-36%. Associated changes in the tolerance factor (1.024 ≤ t ≤ 0.976) and bond angles were observed. Structure assisted B′-B″ cation ordering was confirmed through the superlattice reflections in selected area electron diffraction (SAED) pattern of Pb(Sc0.5Nb0.5)O3 (x = 0.5). Cation ordering is also evident from the evolution of Pb-O phonon mode in Raman spectra of compositions with rhombohedral symmetry (x ≥ 0.3). The high temperature Raman scattering studies show that the B-localized mode [F1u, ∼250 cm−1] and BO6 octahedral rotational mode [F1g, ∼200 cm−1], both originating from polar nano regions (PNRs) behave like coupled phonon modes in rhombohedral symmetry. However, in monoclinic symmetry they behave independently across the transition. Softening of B localized mode across the transition followed by the hardening for all compositions confirms the diffusive nature of the ferroelectric transformation. The presence of correlation between the B localized and BO6 rotational modes introduces a weak relaxor feature for systems with rhombohedral symmetry in PFSN ceramics, which was confirmed from the macroscopic dielectric studies

SIMULTANEOUS ESTIMATION OF DESLORATADINE AND MONTELUKAST IN BULK AND PHARMACEUTICAL FORMULATIONS BY RP-HPLC

A new, simple, precise, accurate and reproducible RP-HPLC method for Simultaneous estimation of Desloratadine and Montelukast in bulk and pharmaceutical formulations. Separation of Desloratadine and Montelukast was successfully achieved on a ECLEPSE XDB C8 (4.6 x 150mm, 5 mm, Make: Waters) or equivalent in an isocratic mode utilizing K2HPO4 buffer (pH: 8.6) Methanol (60:40%v/v) at a flow rate of 0.8 mL/min and elute was monitored at 261 nm, with a retention time of 2.485 and 3.800 minutes for Desloratadine and Montelukast. The method was validated and the response was found to be linear in the drug concentration range of 50 µg/mL to 150 µg/mL for Desloratadine and 50 µg/mL to 150 µg/mL for Montelukast. The LOD and LOQ for Desloratadine were found to be 2.759, 9.195 respectivly. The LOD and LOQ for Montelukast were found to be 2.9091, 9.6970 respectively. This method was found to be good percentage recovery for Desloratadine and Montelukast were found to be 100.00% and 100.00% respectively indicates that the proposed method is highly accurate. The specificity of the method shows good correlation between retention times of standard with the sample so, the method specifically determines the analyte in the sample without interference from excipients of tablet dosage forms. The method was extensively validated according to ICH guidelines for Linearity, Range, Accuacy, Precesion, Specificity and Robustness

Scandium induced structural transformation and B':B' cationic ordering in Pb(Fe0.5Nb0.5)O3 multiferroic ceramics

The current study explores non-magnetic Sc3+ induced structural transformation, evolution of local B-site cation ordering and associated effect on ferroelectric phase transition temperature Tmax (temperature corresponding to dielectric maxima) on increasing the atom percent of Sc substitution in [Pb(Fe0.5Nb0.5)O3 (PFN)] ceramics. In this regard, the phase pure Pb[(Fe0.5-xSc x)Nb0.5]O3 ceramics with x varying from 0 to 0.5 were synthesized through solid state reaction route. The detailed structural analysis through Rietveld refinement confirms the room temperature transformation from a monoclinic Cm to rhombohedral R3m structure at x = 0.3 mol. % of Sc. Absorption spectra studies show that there is a considerable increment in the bandgap at higher scandium content. Most interestingly, the Tmax exhibited an increment for lower scandium contents (x = 0.1 to 0.25) followed by a drop in Tmax (x = 0.3 to 0.5). Such anomalous behavior in Tmax is expected to arise due to the onset of B', B' local cation ordering beyond Sc content x = 0.25. The B-site cation ordering at and beyond x = 0.3 was also confirmed by the evolution of cation order induced Pb-O coupled vibrational mode in Raman scattering studies. In addition, the Mössbauer spectra of PFN (x = 0) and Pb(Fe0.4Sc 0.1Nb0.5)O3 (x = 0.1) are reported to verify the spin state and oxidation state of iron. The lattice distortion due to the radius ratio difference between a Sc3+ cation and Fe3+ cation in low spin state is responsible for the structural transformation, which in turn facilitates a B':B' cation ordering

Effect of crystal structure and cationic order on phonon modes across ferroelectric phase transformation in Pb(Fe0.5-xScxNb0.5)O3 bulk ceramics

Pb(Fe0.5-xScxNb0.5)O3 [(PFSN) (0 ≤ x ≤ 0.5)] multiferroic relaxors were synthesized and the temperature dependence of phonon modes across ferroelectric to paraelectric transition was studied. With varying Sc content from x = 0 to 0.25 the structure remains monoclinic and with further addition (x = 0.3 - 0.5) the structure transforms into rhombohedral symmetry. Structural refinement studies showed that the change in crystal structure from monoclinic to rhombohedral symmetry involves a volume increment of 34-36%. Associated changes in the tolerance factor (1.024 ≤ t ≤ 0.976) and bond angles were observed. Structure assisted B′-B″ cation ordering was confirmed through the superlattice reflections in selected area electron diffraction (SAED) pattern of Pb(Sc0.5Nb0.5)O3 (x = 0.5). Cation ordering is also evident from the evolution of Pb-O phonon mode in Raman spectra of compositions with rhombohedral symmetry (x ≥ 0.3). The high temperature Raman scattering studies show that the B-localized mode [F1u, ∼250 cm−1] and BO6 octahedral rotational mode [F1g, ∼200 cm−1], both originating from polar nano regions (PNRs) behave like coupled phonon modes in rhombohedral symmetry. However, in monoclinic symmetry they behave independently across the transition. Softening of B localized mode across the transition followed by the hardening for all compositions confirms the diffusive nature of the ferroelectric transformation. The presence of correlation between the B localized and BO6 rotational modes introduces a weak relaxor feature for systems with rhombohedral symmetry in PFSN ceramics, which was confirmed from the macroscopic dielectric studies

Development of cerium promoted copper-magnesium catalysts for biomass valorization: Selective hydrogenolysis of bioglycerol

The selective hydrogenolysis of bioglycerol to 1,2-propanediol was investigated over a series of Ce-promoted Cu/Mg catalysts, namely, Cu/Mg (1/9), Cu/Ce/Mg (1/1/5), Cu/Ce/Mg (1/3/5), and Cu/Ce/Mg (1/5/5) prepared by a coprecipitation method. The physicochemical properties of the synthesized catalysts were analyzed by XRD, Raman, BET, BJH, XPS, NH3- and CO2-TPD, and H2-TPR techniques. The XRD and BET surface area results indicated that addition of Ce to Cu/Mg sample remarkably inhibits the crystal growth of CuO and improves the specific surface area. More number of oxygen vacancy defects were found in the Cu/Ce3/Mg sample, as evidenced from Raman studies. The reducible nature of the Cu/Mg sample was significantly enhanced after the Ce-incorporation. The NH3- and CO2-TPD results show that the acid-base properties of the Ce-promoted Cu/Mg samples are highly dependent on the Ce-loading. Among the synthesized samples, the Cu/Ce3/Mg sample exhibited higher concentration and superior strength of acidic sites. The achieved activity order of various catalysts for glycerol hydrogenolysis is Cu/Mg < Cu/Ce1/Mg < Cu/Ce3/Mg < Cu/Ce5/Mg. The high surface area, higher concentration of acid sites, abundant oxygen vacancies, and remarkable reducibility are found to be the key factors for the observed superior performance of the Cu/Ce3/Mg catalyst. Notably, the Cu/Ce3/Mg catalyst could be used multiple times for glycerol hydrogenolysis without considerable loss of activity

Highly efficient continuous-flow oxidative coupling of amines using promising nanoscale CeO<inf>2</inf>-M/SiO<inf>2</inf> (M = MoO<inf>3</inf> and WO<inf>3</inf>) solid acid catalysts

The development of promising solid acid catalysts alternative to hazardous liquid acids is essential towards a sustainable chemical industry. This work reports the synthesis of nanostructured CeO 2 -MoO 3 /SiO 2 and CeO 2 -WO 3 /SiO 2 solid acids, along with CeO 2 -MoO 3 , CeO 2 -WO 3 and CeO 2 for continuous-flow oxidative coupling of benzylamine using O 2 as a green oxidant. A systematic physicochemical characterization has been undertaken using XRD, Raman, N 2 adsorption-desorption, TEM, NH 3 -TPD, and XPS techniques. It was found that the dispersion of CeO 2 -MoO 3 and CeO 2 -WO 3 species on the SiO 2 support leads to remarkable structural and acidic properties, due to the synergetic effect of the respective components. TEM analysis reveals the presence of highly dispersed WO 3 (0.8-1.2 nm) and MoO 3 (0.8-1 nm) nanoparticles in the synthesized catalysts. Among the various catalysts developed, the CeO 2 -MoO 3 /SiO 2 sample exhibited higher BET surface area (248 m 2 g -1 ), abundant oxygen vacancy defects, and large amounts of strong acidic sites. Owing to improved properties, the CeO 2 -MoO 3 /SiO 2 solid-acid showed a superior catalytic performance in the continuous-flow oxidative coupling of benzylamine: the obtained benzylamine conversions for 1 h are ∼11.8, 55, 70, 76, and 96%, respectively, for CeO 2 , CeO 2 -WO 3 , CeO 2 -WO 3 /SiO 2 , CeO 2 -MoO 3 , and CeO 2 -MoO 3 /SiO 2 catalysts. Importantly, the CeO 2 -MoO 3 /SiO 2 solid acid exhibited a remarkable steady performance in terms of benzylamine conversion (∼88-96%) and selectivity of N-benzylbenzaldimine product (∼96-97.8%) up to 6 h. The outstanding catalytic performance of CeO 2 -MoO 3 /SiO 2 solid acid coupled with the application of continuous-flow synthesis, economical benefits of the respective oxides, and eco-friendly oxidant is expected to bring new opportunities in the design of industrially-favourable chemical processes

Nanomechanical behavior of Pb(Fe0.5−xScxNb0.5)O3 multiferroic ceramics

Nanomechanical behavior of Pb(Fe0.5−xScxNb0.5)O3 [(PFSN) (0 ≤ x ≤0.4)] was investigated with systematic variation in Sc content to capture the effect of doping induced structural phase transition on mechanical properties. Reduced modulus initially decreased with increase in doping concentration up to 0.2% of Sc content and then showed increment with further addition of Sc. In situ nanoindentation has been carried out from room temperature to 140 °C to measure the variation in reduced modulus and hardness values with temperature in Pb(Fe0.5Nb0.5)O3 without Sc addition. Hardness and reduced modulus values of Pb(Fe0.5Nb0.5)O3 were found increase from 60 to 100 °C indicating the role of phase transition