An effective interionic potential calculation with long range Coulomb, charge transfer interaction, covalency effect, short range overlap repulsion extended, van der Waals interaction, and zero point energy effect is implemented to investigate the pressure dependent structural phase transition (ZnS-type (B3) to NaCl-type (B1) structure), and mechanical, elastic, and thermodynamic properties of silicon carbide (SiC). Both charge transfer interaction and covalency effect are important in revealing the pressure induced structural stability, Cauchy discrepancy, anisotropy factor, melting temperature, shear modulus, Young’s modulus, and Grüneisen parameter. We also present the results for the temperature dependent behaviors of normalized volume, hardness, heat capacity, and thermal expansion coefficient. SiC is mechanically stiffened and thermally softened as inferred from pressure (temperature) dependent elastic constant’s behavior. The Pugh’s ratio $\varphi =B_{\text{T}}/G_{\text{H}}$, the Poisson’s ratio ν, and the Cauchy’s pressure C₁₂–C₄₄ for SiC ceramic confirm its brittle nature.

In this study, bulk samples of multiferroic with compositional formula, BiFeO₃ and Bi_0.825A_0.175FeO₃ (A=La, Pb), were synthesized by solid state reaction route. X-ray diffraction (XRD) along with the Rietveld refinement revealed the distorted rhombohedral (R3c) structure for pristine BiFeO₃ and Bi_0.825La_0.175FeO₃ and tetragonal (P4/mmm) for Bi_0.825Pb_0.175FeO₃ ceramic. To support the structural results, bond length between atoms for both of the compounds was calculated. A change in Raman mode position in BiFeO₃ (BFO) has been observed with La and Pb substitution from Raman scattering measurements and also recommended a structural change with rare earth and metal ion substitution at Bi site. From the frequency dependent dielectric constant and dielectric loss plots, a decrease in dielectric values with increase in frequency was observed for both of the samples. For microelectronic devices, porous ceramics with lower value of dielectric constant are most useful. Thus, further studies are also needed to carefully tune the magnetoelectric properties and structural distortion after La/Pb substitution in BFO.

Ti doped hematite α-Fe_2-xTi_xO₃ (x = 0.0, 0.0206 and 0.0344) samples are synthesized using solid-state ceramic route technique. Single phase and corundum (Al₂O₃) type structure is revealed from the X-ray diffraction (XRD) pattern. On substitution of Ti at Fe site, all Raman active modes are shifted to higher wave numbers. An additional feature of E_u (LO) mode at about 660 cm^–1 is observed. The E_u mode frequency is decreased and pronounced systematically as a function of Ti doping, and it reaches a value of 658 cm^-1 for x = 0.0344. The coercivity H_c (remanence M_r) for x = 0.0, 0.0206 and 0.0344 are determined to be 995 Oe (0.44 emu/mg), 1404 Oe (0.00019 emu/mg) and 2023 Oe (0.00016 emu/mg), respectively. The larger coercivity for Ti doped samples can be attributed to their enhanced shape and magneto-crystalline anisotropy. The observed isomer shift (δ) from room temperature Mössbauer data clearly shows the presence of ferric (Fe³⁺) and Ti⁴⁺ ions illustrating strong ferromagnetic ordering up to x = 0.0206 in α-Fe_2-xTi_xO₃ hematite and weak ferromagnetic ordering of α-Fe_2-xTi_xO₃ for x = 0.0344.

We develop a theoretical model for quantitative analysis of temperature-dependent thermoelectric power of monovalent (Na) doped La_0.97Na_0.03MnO₃ manganites. In the ferromagnetic regime, we have evaluated the phonon thermoelectric power by incorporating the scattering of phonons with impurities, grain boundaries, charge carriers and phonons. In doing so, we use the Mott expression to compute the carrier (hole) diffusion thermoelectric power ( $S_{\text{c}}^{\text{diff}}$) using Fermi energy as carrier (hole)-free parameter, and $S_{\text{c}}^{\text{diff}}$ shows linear temperature dependence and phonon drag $S_{\text{ph}}^{\text{drag}}$ increases exponentially with temperature which is an artifact of various operating scattering mechanisms. It is also shown that for phonons the scattering and transport cross-sections are proportional to ω⁴ in the Rayleigh regime where ω is the frequency of the phonons. Numerical analysis of thermoelectric power from the present model shows similar results as those revealed from experiments.

Solid-state ceramic technique route is used for synthesizing Cr-doped haematite α-Fe_2-xCr_xO₃ (x = 0, 0.125, 0.50 and 1) samples. Single phase and corundum (Al₂O₃) type structure is revealed from the X-ray diffraction (XRD) patterns. The Raman spectra of α-Fe_2-xCr_xO₃ illustrate seven phonon modes. On substitution of Cr (x = 0, 0.125, 0.50 and 1) at Fe site, all Raman active modes are shifted to higher wave numbers. The coercivity and remanence of Cr-doped haematites increase as x increases. The increased coercivity and remanence for Cr-doped samples can be attributed to their enhanced shape and magneto-crystalline anisotropy. The observed isomer shift δ values from room-temperature Mössbauer data clearly show the presence of ferric (Fe³⁺) and Cr³⁺ ions illustrating strong ferromagnetic ordering up to x = 0.125 in α-Fe_2-xCr_xO₃ haematite and weak ferromagnetic ordering for α-Fe_2-xCr_xO₃ (x > 0.125) haematites.