O P Shrivastava
Articles written in Bulletin of Materials Science
Volume 23 Issue 6 December 2000 pp 515-520 Cements
Immobilization and solidification of hazardous cations like Cs137 and Sr90 are required while handling the radioactive waste of nuclear power plants. Efforts are on to find a fail proof method of safe disposal of nuclear wastes. In this context, various materials like borosilicate glass, zeolites, cements and synthetic rocks have been tried by several workers. This communication deals with the synthesis, characterization, cesium uptake capacity and leaching behaviour of synthetic alumina-substituted calcium silicate hydroxy hydrate, which are close to that obtained for the natural mineral,
Volume 27 Issue 2 April 2004 pp 121-126 Synthesis
Perovskite structure based ceramic precursors have a characteristic property of substitution in the ``A" site of the ABO3 structure. This makes them a potential material for nuclear waste management in synthetic rock (SYNROC) technology. In order to simulate the mechanism of rare earth fixation in perovskite, La𝑥 Ca1-𝑥TiO3 (where 𝑥 = 0.05) has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and La as starting materials. Solid state synthesis has been carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050°C. The ceramic phase has been characterized by its powder diffraction pattern. Step analysis data has been used to determine the structure of solid solution of lanthanum substituted calcium titanate. The SEM and EDAX analyses also confirm that the CaTiO3 can act as a host for lanthanum. X-ray data has been interpreted using CRYSFIRE and POWDERCELL softwares. The ℎ, 𝑘, 𝑙 values for different lattice planes have been generated from the experimental data. The lanthanum substituted perovskite crystallizes in orthorhombic symmetry with space group 𝑃 𝑛 𝑚 𝑎 (#62). Following unit cell parameters have been calculated: 𝑎 = 5.410, 𝑏 = 7.631, 𝑐 = 5.382. The calculated and observed values of corresponding intensities, 2𝜃, and density show good agreement. GSAS based calculation for bond distances Ti–O, Ca–O, La–O and bond angles Ti–O–Ca, Ca–O–Ca, La–O–Ti have been reported.
Volume 34 Issue 1 February 2011 pp 89-95
The perovskite ceramic phases with composition Ca1−𝑥Y𝑥TiO3+𝛿 (where 𝑥 = 0.1, 0.2 and 0.3; hereafter CYT-10, CYT-20 and CYT-30) have been synthesized by solid state reaction at 1050°C. The structure refinement using general structure analysis system (GSAS) software converges to satisfactory profile indicators such as Rietveld parameters: Rp, Rwp, RF2 and goodness of fit. The title phases crystallize at room temperature in the space group 𝑃𝑏𝑛𝑚 (#62) with 𝑎 = 5.3741(4) Å, 𝑏 = 5.4300(4) Å, 𝑐 = 7.6229(5) Å and 𝑍 = 4. Major interatomic distances, bond angles and structure factors have been calculated from the step analysis data of the compound. The crystal morphology has been examined by scanning electron microscopy. Energy dispersive X-ray (EDX) analysis of the specimens show that yttrium enters into the structural framework of CaTiO3. The particle size of the ceramic phases along major reflection planes ranges between 12 and 40 nm. The polyhedral (CaO8 and TiO6) distortions and valence calculations from bond strength data are also reported.
Volume 43, 2020
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