M A Ittyachen
Articles written in Bulletin of Materials Science
Volume 6 Issue 6 December 1984 pp 997-1000
The results obtained from etching experiments on the habit faces of NiMoO4·
Volume 15 Issue 4 August 1992 pp 349-353
Molybdate crystals doped with rare-earth ions are finding immense use as laser materials. Rare-earth mixed single crystals of samarium barium molybdate grown in silica gel are important for use in optical equipment and electronic and acoustic studies. These octahedral bipyramidal crystals of samarium barium molybdates are characterized by IR, EDAX and thermal analyses.
Volume 17 Issue 7 December 1994 pp 1447-1455
Sparingly soluble neodymium copper oxalate (NCO) single crystals were grown by gel method, by the diffusion of a mixture of neodymium nitrate and cupric nitrate into the set gel containing oxalic acid. Tabular crystal, revealing well-defined dissolution figures has been recorded. X-ray diffraction studies of the powdered sample reveal that NCO is crystalline. Infrared absorption spectrum confirmed the formation of oxalato complex with water of crystallization, while energy dispersive X-ray analysis established the presence of neodymium dominant over copper in the sample. X-ray photoelectron spectroscopic studies established the presence of Nd and Cu in oxide states besides (C2O4)2− oxalate group. The intensities of Nd (3
Volume 19 Issue 3 June 1996 pp 495-504
Praseodymium barium molybdate (PBM) single crystals grown by gel method, reveal multiple and isolated octahedral bipyramidal crystals as well as spherulites of PBM at different depths from the surface inside the gel. Oscillation X-ray diffraction pattern of the sample reveals that PBM is single crystalline in nature. Infrared absorption spectrum confirms the presence of molybdate (MoO4)2− ions in PBM, while the thermogravimetric analysis shows that PBM loses molybdenum oxide component around 420°C. Energy dispersive X-ray analysis establishes the presence of Pr, Ba and Mo in the sample. X-ray photoelectron spectroscopic studies of PBM establish the presence of Pr, Ba and Mo in their respective oxide states. An empirical structure has been proposed on the basis of these findings. The implications are discussed.
Volume 20 Issue 1 February 1997 pp 37-48
The mixed crystals of neodymium praseodymium oxalate are grown by the diffusion of a mixture of aqueous solutions of neodymium nitrate and praseodymium nitrate (as an upper reactant) into the set gel embedded with oxalic acid. By varying the concentration (by volume) of rare earth nitrates in the upper reactant, the incorporation of Nd and Pr in the mixed crystals has been studied. Tabular crystals with the well defined hexagonal basal planes are observed in the mixed crystals of varying concentrations. X-ray diffraction patterns of these powdered samples reveal that these mixed crystals are ‘isostructural’, while IR and FTIR spectra establish the presence of oxalate groups. TGA and DSC analyses show the correctness of the chemical formula for the mixed crystals, by the release of water molecules (endothermic) and of CO and CO2 (exothermic), with the rare earth oxides as the stable residue. X-ray fluorescence (XRF) and energy dispersive X-ray analyses (EDAX) establish the presence of heavy rare earth elements qualitatively and to a good extent quantitatively. X-ray photoelectron spectroscopic (XPS) studies confirm the presence of rare earth elements (Nd and Pr) as their respective oxides. The findings of these techniques of characterization are in excellent agreement with the proposed empirical structure for the mixed rare earth oxalates. The implications are discussed.
Volume 20 Issue 2 April 1997 pp 231-238
Thermodynamical feasibility study and the growth of layer structured transition metal dichalcogenide single crystals of WSe2, using iodine as transporting agent, has been reported in this paper. The characterization of the grown samples have been done by X-ray analysis.
Volume 20 Issue 8 December 1997 pp 1059-1068
Lanthanum samarium oxalate (LSO) single crystals are grown in silica gels by the diffusion of a mixture of aqueous solutions of lanthanum nitrate and samarium nitrate into the test tube having the set gel impregnated with oxalic acid. Tabular crystals of LSO having well defined hexagonal basal planes are observed at different depths inside the gel. LSO crystals grown by this method are colourless and transparent. Laue transmission X-ray diffraction pattern of LSO reveals well defined spots with two-fold symmetry along the horizontal axis. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) support that LSO loses water around 120°C, and CO and CO2 around 350–450°C. The infrared (IR) absorption spectrum of LSO establishes the presence of oxalate (C2 O4)2− ions. Energy dispersive X-ray analysis (EDAX) confirms the presence of La and Sm in the sample. X-ray photoelectron spectroscopic (XPS) studies of LSO confirm the presence of La and Sm in their respective oxide states. An empirical structure for LSO has been proposed on the basis of these findings.
Volume 21 Issue 5 October 1998 pp 375-380 Materials Preparation
Single crystals of lanthanum neodymium oxalate (LNO) are grown in sodium meta silicate gels, by the diffusion of a mixture of aqueous solutions of lanthanum nitrate and neodymium nitrate into the test tube having the set gel containing oxalic acid. The bluish pink coloured tabular crystals of LNO having well defined hexagonal basal planes appear either as ‘foggy’ or ‘clear’, the latter at the greater depths inside the gel. The colouration of LNO visually observed is evidenced in UV-visible spectrum, by the revelation of well pronounced characteristic peaks in the visible region (500–900 nm). X-ray diffraction (XRD) of powdered LNO is ordered, meaning crystalline in nature, besides its ‘isostructurality’ with similarly grown lanthanum samarium oxalate crystals. The single crystallinity of LNO is established by its oscillation XRD pattern. Thermogravimetric analysis (TGA) and differential scanning colorimetry (DSC) support that LNO loses water of crystallization around 120°C and CO and CO2 around 350–450°C, while the infrared absorption (IR) spectrum of LNO establishes the presence of oxalate (C2O4)2− ions. Energy dispersive X-ray analysis (EDAX) confirms the presence of La and Nd in the sample. X-ray photoelectron spectroscopic (XPS) studies of LNO establish the presence of La and Nd in their respective oxide states. An empirical structure for LNO has been proposed on the basis of these findings. The ‘smokiness’ in the foggy LNO crystal has been attributed due to the ‘gel inclusion’ during the growth process.
Volume 21 Issue 5 October 1998 pp 387-391 Materials Preparation
Single crystals of cerium oxalate are grown by the gel method. Ce(NO3)3 is allowed to diffuse into a gel in which oxalic acid is incorporated. Cerium oxalate crystals are formed by chemical reaction and the growth process is observed. Crystals are yellow-white in colour. Morphology and size of the crystals are highly influenced by the acidity of the feed solution. With 30% HNO3 long needle shaped, with 50% HNO3 thin hexagonal and with 100% HNO3, well developed crystals are obtained. Natural etch pits are observed on the grown crystals due to the presence of HNO3. Appearance of a single, large interfacial crystal is observed for 0·5 M cerium nitrate. IR spectrum confirms the presence of water molecules and carboxylic group. X-ray diffractogram gives well defined peaks. Peaks are indexed. Unit cell dimensions are determined. Thermal analysis of the samples done using TGA and DTA show the release of water molecules (endothermic) and of CO and CO2 (exothermic) with the rare earth oxide as stable residue.
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