• RICHA TOMAR

      Articles written in Bulletin of Materials Science

    • Microwave dielectrics: solid solution, ordering and microwave dielectric properties of $(1−x)$Ba(Mg$_{1/3}$Nb$_{2/3}$)O$_3$−$x$Ba(Mg$_{1/8}$Nb$_{3/4}$)O3 ceramics

      YOGITA BISHT RICHA TOMAR PULLANCHIYODAN ABHILASH DEEPA RAJENDRAN LEKSHMI M THIRUMAL

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      The effect of Ba(Mg$_{1/8}$Nb$_{3/4}$)O$_3$ phase on structure and dielectric properties of Ba(Mg$_{1/3}$Nb$_{2/3})O$_3$ was studied by synthesizing $(1−x)$Ba(Mg$_{1/3}$Nb$_{2/3}$)O$_{3}$−$x$Ba(Mg$_{1/8}$Nb$_{3/4}$)O$_3$ ($x = 0,$ 0.005, 0.01 and 0.02) ceramics. Superlattice reflections due to 1:2 ordering appear as low as 1000$^{\circ}$C. Ba(Mg$_{1/3}$Nb$_2/3}$)O$_3$ forms solid solution with Ba(Mg$_{1/8}$Nb$_{3/4}$)O$_3$for all ‘$$x’ values studied until 1350$^{\circ}$C. Ordering as confirmed by powder X-ray diffraction pattern, Raman study andHRTEM. Ceramic pucks can be sintered to density $>$92% of theoretical density. Temperature and frequency-stable dielectricconstant and nearly zero dielectric loss ($\tan \delta$) were observed at low frequencies (20 MHz). The sintered samples exhibit dielectric constant ($\epsilon_\tau$) between 30 and 32, high quality factor between 37000 and 74000 GHz and temperature coefficient of resonant frequency ($\tau_f$ ) between 21 and 24 ppm$^{\circ}$C$^{−1}$.

    • Chromium-doped Y$_{0.50}$Gd$_{0.50}$BO$_3$ as an excellent photocatalytic and magnetic material

      PANKAJ GUPTA RICHA TOMAR N B SINGH

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      Crystalline chromium-doped Y$_{0.50}$Gd$_{0.50}$BO$_3$ with vaterite structure was synthesized by the calcination of gel from the reaction of yttrium borate, gadolinium borate, boric acid and propylene oxide at 900°C for 4 h. Orthoborates containing 10 and 20 mol% chromium-doped samples were successfully obtained and characterized by various techniques. Photoluminescent studies were performed for the doped samples. The optical bandgap of chromium-doped samples falls in the visible region making the material more viable for photocatalytic activities. The sample was used as a photocatalyst for photodegradation of methylene blue dye. Y$_{0.50}$Gd$_{0.50}$BO$_3$ and chromium-doped samples showed good magnetic properties, as they are antiferromagnetic in nature. To the best of our knowledge, the vaterite form of chromiumdoped Y$_{0.50}$Gd$_{0.50}$BO$_3$ has been synthesized for the first time.

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    • 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

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

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      Posted on July 25, 2019

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