• D KUMAR

Articles written in Bulletin of Materials Science

• Oxygen incorporation duringin situ growth of YBCO films on both sides of substrates

Oxygen out-diffusion during cooling and heating ofin situ grown {ie685-1} (YBCO) films in low oxygen pressure used during growth by pulsed laser deposition was studied in the temperature range 700−450°C usingin situ resistance measurements. Results indicate that irrespective of the number of cooling and heating cycles seen by the films, full oxygenation of the films can be realized by the final cooling from the growth temperature in 500 torr oxygen pressure. This result has been successfully used to sequentially grow high quality YBCO films on both sides of LaAlO3 substrates. These films have been used for the fabrication of X-band microstrip resonators with superconducting ground plane.

• Investigation of dielectric relaxation in dipolar liquids from conductivity measurement

Conductivity (σ$_{ijk}$’s) measurement method is proposed to investigate dielectric relaxation in ternary polar–nonpolar mixture of N,N-dimethyl formamide (DMF)(j) with pyridine(k) or acetonitrile(k) dissolved in p-xylene (i) at various weight fractions (w$_{jk}$’s) and temperature under different bands (S, C, X and Ku) of microwave field applying Debye’s dielectric model. Ratio of slopes of imaginary σ$_{ijk}$″ vs. w$_{jk}$ with real σ$_{ijk}$′ vs. w$_{jk}$ of complex conductivity σ$_{ijk}$* as well as linear slope of σ$_{ijk}$″ vs. σ$_{ijk}$′ are used to predict τ$_{jk}$’s (relaxation time) and μ$_{jk}$’s (dipole moments). Variousmolecular associations are also identified from the meaningful interactions among polar–nonpolar molecules in terms of τ$_{jk}$ and μ$_{jk}$. Molecular dynamics or molecular environment surrounding the polar molecules DMF, pyridine or acetonitrileis extensively studied with the help of estimated thermodynamic energy parameters. The existence of Debye relaxation mechanism in polar–nonpolar mixture is authenticated by the estimated Debye factor. Microwave sensor development is also ascertained from various dielectric parameters like permittivity, conductivity and penetration depth under microwave field.

• # Bulletin of Materials Science

Volume 45, 2022
All articles
Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020