Processing studies on varied shape-forming and densification of bulk ceramic superconductor, YBa_1·5Ca_0·5Cu₃O_7\t-\gd, are reported in this paper. Polyvinyl butyral-polyethylene glycol-trichloroethylene has been found to be the best binder-plasticizer-solvent system in plastic shape-forming. The effect of initial particle morphology on final densification has been the most sensitive single parameter as compared to compaction pressure and final sintering durations at ∼930°C. 1-2-3 powders of mean particle size ∼ 1·94 µm have yielded sintered densities ∼92% T.D. albeit with lower oxygen intake O_6·7.

Mechanochemically activated reactants were found to facilitate the synthesis of fine powders comprising 200–400 nm range crystallites of BaBi₄Ti₄O₁₅ at a significantly lower temperature (700 °C) than that of solid-state reaction route. Reactants (CaCO₃, Bi₂O₃ and TiO₂) in stoichiometric ratio were ball milled for 48 h to obtain homogeneous mixture. The evolution of the BaBi₄Ti₄O₁₅ phase was systematically followed using X-ray powder diffraction (XRD) technique. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to probe its structural and microstructural details. The electron diffraction studies established the presence of correlated octahedral rotations and associated long-range polar ordering. High-resolution TEM imaging nevertheless revealed structural inhomogeneities leading to intergrowth defects. Dense BaBi₄Ti₄O₁₅ ceramics with an average grain size of 0.9 𝜇m were fabricated using mechanochemically assisted synthesized powders at relatively low temperature (1000 °C). The effect of grain size on the dielectric and relaxor behaviour of BaBi₄Ti₄O₁₅ ceramics was investigated. Fine-grained ceramics (average grain size ∼ 0.9 𝜇m) showed higher diffusion in phase transition, lower temperature of phase transition, lower Vogel–Fulcher freezing temperature and higher activation energy for the polarization reversal than those for coarse-grained ceramics (average grain size ∼ 7 𝜇m) fabricated via the conventional solid-state reaction route.

Atomistic simulations of cracks with four different orientations in body-centered cubic single crystal iron are presented using molecular dynamics. Crystal orientation has considerable effect on the activation and evolution ofcrack propagation mechanisms. The results reveal that (a) crack-tip blunting depends on the crystallographic orientation, (b) continuous generation of dislocations form crack tip occurs for large crack-tip blunting, and (c) absence of deformation activities like dislocation generation, twin formation, etc. at the crack tip results in crack propagation in a brittle manner.

Chemical detection of toxic gases, such as greenhouse gases is still very important as a research topic. To design gas sensor detectors based on single-walled carbon nanotubes (SWCNTs) with high sensitivity and selectivity for the toxic environment is a continuous process. The aim is to detect NO$_2$ gas with better sensitivity. In the present work, the thin-film sensor is fabricated on SiO$_2$ substrate and it is functionalized with polyethylenimine (PEI). It has been established that PEI functionalized SWCNTs (F-SWCNTs) show high sensitivity towards strong electron-withdrawing particles. It was found that at room temperature, SWCNTs-PEI functionalized gas sensor exhibited a higher sensitivity of 37.00% as compared with bare SWCNTs gas sensor. The gas sensor has shown the repeatable response for the entire concentration range studied.The sensing properties and the PEI functionalization duration effects on the behaviour of SWCNTs-based gas sensors were demonstrated.

The present investigation focuses on understanding the structure–electric conductivity correlation in NASICON-type LiSn$_2$(PO$_4$)$_3$ (LSP) powders prepared via solid-state reaction method. LSP powders synthesized at different temperatures were characterized for their structural and electrical properties using lab source powder X-ray diffraction (XRD), high-resolution synchrotron X-ray diffraction (SXRD) and complex impedance spectroscopy. LSP powders prepared in 900–1000°C temperature crystallize in triclinic structure (space group, P $\bar{1}$) along with the small amount of SnO$_2$ (P4$_2$/mnm) impurity phase. Samples prepared at temperatures in 1050–1250°C range showed a mixed rhombohedral (R $\bar{3}$c) and triclinic structure with the fraction of the triclinic phase decreasing with an increase in calcination temperature. On further increase in the calcination temperature to 1300°C, LSP transformed to the rhombohedral structure. Moreover, temperature-dependent SXRD confirmed that the LSP powder exhibits a martensitic behaviour, where a pure triclinic structure transforms into a pure rhombohedral phase at 170°C and retains a partial rhombohedral phase on cooling back to room temperature. The highest value of conductivity was found to be ${\sim}$1.06 ${\times}$ 10$^{–6}$ Scm$^{–1}$ for the LSP powder with triclinic structure calcined at 900°C, with an associated activation energy of ${\sim}$0.24 eV. Rhombohedral LSP calcined at 1300°C exhibits the lowest conductivity and highest activation energy at room temperature ${\sim}$1.12 ${\times}$ 10$^{–8}$ Scm$^{–1}$ and ${\sim}$0.39 eV, respectively. This decrease in conductivity for the supposedly highconducting rhombohedral phase is attributed to the drastic increase in the fraction of the SnO$_2$ impurity phase, as confirmed by the XRD analysis.

The exploration of mechanical properties and formation of various crystal structures under the mechanically stressed condition has numerous uses for the design of engineering components for electronic instruments, automotive,aerospace, etc. In order to diagnose the stress–strain behaviour and growth coalescence of crystalline structures in singlecrystal iron during bi-axial tensile deformation, classical molecular dynamics (MD) simulation has been employed. Twostage atomistic structural transformations in single-crystal iron are observed. First-stage transformation corresponds to body-centred cubic (bcc) to face-centred cubic (fcc) crystal, whereas the second-phase transformation corresponds to fccto bcc. To gain further insights, multiple MD simulations have been performed by varying the strain rate of the tensile deformation. Common neighbour analysis, dislocation analysis and stress–strain analysis have been used to precisely characterize the simulation trajectories during simulations. Outcomes of our work will provide additional insights for improved design of engineering components.