• A A DAKHEL

Articles written in Bulletin of Materials Science

• Physicochemical, structural and induced ferromagnetic properties of Co–In-codoped CdO synthesised via Cd chloride: significant effect of post-treatment hydrogen

Nanoparticle solid solution powders of cadmium oxide doped with different concentrations of cobalt and indium ions were synthesised by solvothermal method through CdCl$_2$·H$_2$O precursor route. The objective of the present work is to study and develop conditions necessary to create stable room-temperature ferromagnets (RTFMs) in transparent conducting oxide (TCO) CdO for applications in the field of dilute magnetic semiconductors (DMSs). To achieve this aim, cobalt (Co$^{2+}$) dopant ions were used as a source of stable FM, while In$^{3+}$ dopant ions supply free electrons that enhance the electronic medium of interaction. The electronic medium in the host CdO lattice,which carries the long-range spin–spin ($S.S$) exchange interaction between localised Co$^{2+}$ (3d) spins of dopant ions, was further developed by annealing in hydrogen gas (hydrogenation). The crystalline structure of the powder samples was investigated by the X-ray diffraction (XRD) method. The optical absorption properties were studied by diffuse reflection spectroscopy (DRS). Magnetic measurements reveal that the Co–In-codoped CdO powder has FM properties superimposed on paramagnetic (PM) behaviour. However, annealing in hydrogen atmosphere strongly boosts the created FMso that the saturation magnetisation increases $\sim$90 times. Physical explanations and discussion are given in the article. Thus, it is proved that the magnetic properties could be tailored to TCO CdO by Co-doping and post-treatment under H$_2$ atmosphere.

• Comparative study of structural, optical and magnetic properties of Fe–Pt, Fe–Cu and Fe–Pd-codoped WO$_3$ nanocrystalline ceramics: effect of annealing in hydrogen atmosphere

Tungsten oxide(W-oxide) nanoparticles doped and codopedwith different transition-metal (TM) ions (Fe, Pt, Cu and Pd) were synthesized by hydrochloric acid-assisted precipitation. The synthesized powders were characterized by X-raydiffraction (XRD), diffuse reflectance spectroscopy (DRS) and magnetic characterization methods. The room temperature (RT) monoclinic (P21/n) structure founded for pristine WO$_3$ nanopowder was converted into orthorhombic (Pbam) structure by Fe-doping, while codoping, (Fe–Pt) and (Fe–Cu) preserved the P21/n space group (SG) structure. It was found that thehydrogenation of the synthesized doped-samples corroded the crystallites without changing the crystalline SG structure. Moreover, controllable room temperature ferromagnetic (RT-FM) properties were created by hydrogenation of the codoped W-oxide samples. The oxygen vacancies-mediated ferromagnetic (FM) interaction could be responsible for the observed FM. The relative highest RT-FM energy was created with hydrogenated Fe–Pd codopedW-oxide. Therefore, Fe–Pd-codoped W-oxide nanopowder could be considered as a potential candidate for many applications involving partial FM properties,such as catalysts and optical phosphors.

• Influence of incorporation of carbon on the transparent conducting properties of CdO thin films

Thin films of CdO incorporated with different amounts of carbon element have been deposited on glass substrates by using the vacuum thermal evaporation method aiming at improving their transparent conducting (TC) properties. Thestructural and opto-electrical properties of the host CdO films were systematically studied. X-ray diffraction and optical investigations confirmed the inclusion of C species in the CdO lattice. The obtained results were explained through theoccupation of interstitial positions and structural vacancies of the host CdO lattice by C species. It was observed that the inclusion of carbon into the CdO lattice blue-shifted the optical band gap by $\sim$5−7%, which was attributed to the Moss–Burstein (B–M) effect. The electrical studies showed that the carrier mobility increased steadily with the increase in the C% inclusion level, so that with 5 wt% it attained $\sim$7.5 times the carrier mobility in un-doped CdO. Therefore, the present study showed that the prepared host CdO–C films have controllable TC degenerate semiconducting properties, which could berequired in different optoelectronic applications.

• Bulletin of Materials Science

Volume 44, 2021
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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