Anumeet Kaur | Searcharxiv

arXiv2019

Structural, Electrical, Magnetic and Impedance Behaviour of NdFeO3 Modified Ba0.7Sr0.3TiO3 Ceramics

NdFeO3 modified polycrystalline ceramics with composition (NdFeO3)0.1-(Ba0.7Sr0.3TiO3)0.9 (NFBST) ceramics have been synthesized via solid-state reaction route. The Rietveld refinement of the XRD data confirmed the existence of a tetragonal phase (P4mm) and a hexagonal phase (P63/mmc) in the prepared sample. The coexistence of phases has been also further confirmed from the Raman spectroscopy. The SEM image revealed dense microstructure with well packed grains of different sizes. At room temperature lossy P-E loop and weak ferromagnetism is observed in NFBST system. Complex impedance spectroscopy (CIS) as a function of frequency (100 Hz to 1 MHz) at different temperatures (RT to 700K) has been employed to study the electrical behaviour in NFBST ceramic. Two semicircular arcs in the Cole-Cole plot manifested the grain and grain boundary contribution in overall impedance. The detail complex modulus analysis and ac fitted conductivity data authenticated correlated barrier hopping CBH to be responsible for electrical as well as conduction phenomena in NFBST. Oxygen vacancies are responsible for relaxation and conduction processes in NFBST ceramics as divulged from the activation energy values estimated from electrical impedance, modulus, and conductivity data.

cond-mat.mtrl-sci↗

arXiv2019

Orbital hybridization induced band offset phenomena in NixCd1-xO thin films

We present the cationic impurity assisted band offset phenomena in NixCd1-xO (x= 0, 0.02, 0.05, 0.1, 0.2, 0.4, 0.8, 1) thin films and further discussed in the light of orbital hybridization modification. Compositional and structural studies revealed that cationic substitution of Cd2+ by Ni2+ ions leads to a monotonic shift in (220) diffraction peak, indicating the suppression of lattice distortion while evolution of local strain with increasing Ni concentration mainly associated to the mismatch in electro-negativity of Cd2+ and Ni2+ ion. In fact, Fermi level pinning towards conduction band minima takes place with increasing Ni concentration at the cost of electronically compensated oxygen vacancies, resulting modification in the distribution of carrier concentration which eventually affects the band edge effective mass of conduction band electrons and further endorses band gap renormalization. Besides that, the appearance of longitudinal optical (LO) mode at 477 cm-1 as manifested by Raman spectroscopy also indicate the active involvement of electron-phonon scattering whereas modification in local coordination environment particularly anti-crossing interaction in conjunction with presence of satellite features and shake-up states with Ni doping is confirmed by X-ray absorption near-edge and X-ray photoelectron spectroscopy studies. These results manifest the gradual reduction of orbital hybridization with Ni incorporation, leading to decrement in the band edge effective mass of electron. Finally, molecular dynamics simulation reflects 13% reduction in lattice parameter for NiO thin film as compared to undoped one while projected density of states calculation further supports the experimental observation of reduced orbital hybridization with increasing Ni concentration.

cond-mat.mtrl-sci↗