• SONAL SINGHAL

      Articles written in Bulletin of Materials Science

    • Spin canting phenomenon in cadmium doped cobalt ferrites, CoCd𝑥Fe2−𝑥O4 (𝑥 = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), synthesized using sol–gel auto combustion method

      Sonal Singhal Sheenu Jauhar Kailash Chandra Sandeep Bansal

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      Synthesis of non-collinear (spin canted) ferrites having the formula, CoCd𝑥Fe2−𝑥O4 (𝑥 = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), has been carried out using the sol–gel auto combustion method. The ferrite samples show an interesting magnetic transition from Neel to Yafet–Kittel configuration, as the Cd2+ concentration is increased beyond 𝑥 = 0.4. The FT–IR spectra confirm the formation of the metal oxide bond as they exhibit two frequency bands in the range of ∼595 cm-1 and ∼450 cm-1, corresponding to the tetrahedral and the octahedral stretching vibrations of the metal oxide, respectively. The structural evolutions of the nanophase investigated using powder X-ray diffraction (XRD) technique show that the average crystallite size is ∼35 nm. The magnetic studies reveal that the saturation magnetization, 𝑀s, increases up to 𝑥 = 0.4 and decreases when the value of 𝑥 is > 0.4. It is proposed that the incorporation of Cd2+ ion takes place into the tetrahedral sites and up to 𝑥 = 0.4, Neel’s model is followed. But for 𝑥 > 0.4, canting of spins occurs, as explained by Yafet–Kittel (Y–K) model. The d.c. resistivity decreases as a function of temperature, indicating semiconducting nature of the ferrites and the positive value of Seebeck coefficient establishes 𝑝-type conduction behaviour for all the ferrite samples.

    • Effect of annealing temperature and CdCl$_2$ treatment on the photo-conversion efficiency of CdTe/Zn$_{0.1}$Cd$_{0.9}$S thin film solar cells

      SONAL SINGHAL AMIT KUMAR CHAWLA HARI OM GUPTA RAMESH CHANDRA

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      We report the effects of annealing in conjunction with CdCl$_2$ treatment on the photovoltaic properties of CdTe/Zn$_{0.1}$Cd$_{0.9}$S thin film solar cells. CdTe layer is subjected to dry CdCl$_2$ treatment by thermal evaporation method and subsequently, heat treated in air using a tube furnace from 400 to 500$^{\circ}$C. AFM and XRD results show improved grain size and crystallographic properties of the CdTe film with dry CdCl$_2$ treatment. This recrystallization and grain growth of the CdTe layer upon CdCl$_2$ treatment translates into improved photo-conversion efficiencies of CdTe/Zn$_{0.1}$Cd$_{0.9}$S cell. The results of dry CdCl$_2$ treatment were compared with conventional wet CdCl$_2$ treatment. Photo-conversion efficiency of 5.2% is achieved for dry CdCl$_2$-treated cells in comparison with 2.4% of wet-treated cell at heat treatment temperature of 425$^{\circ}$C.

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      Posted on October 12, 2020

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

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
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      Posted on July 25, 2019

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