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Structural, vibrational, and enhanced magneto-electric coupling in Ho-substituted BiFeO<sub>3</sub>
Muneeswaran, Muniyandi,Lee, Seung Hoon,Kim, Dong Hun,Jung, Beon Sung,Chang, Seo Hyoung,Jang, Jae-Won,Choi, Byung Chun,Jeong, Jung Hyun,Giridharan, N.V.,Venkateswaran, C. Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.750 No.-
<P><B>Abstract</B></P> <P>The effect of Holmium (Ho) substitution in BiFeO<SUB>3</SUB> [Bi<SUB>1-x</SUB>Ho<SUB>x</SUB>FeO<SUB>3</SUB> (x = 0.00, 0.05, 0.10, 0.15, 0.18, and 0.20)] ceramics is reported. The X-ray diffraction study shows composition-driven rhombohedral-to-orthorhombic (<I>R</I>3<I>c</I> to <I>Pnma</I>) phase transition for Bi<SUB>1-x</SUB>Ho<SUB>x</SUB>FeO<SUB>3</SUB> (x = 0.15, 0.18, and 0.20) which is confirmed by Reitveld refinement. Raman spectra of Bi<SUB>1-x</SUB>Ho<SUB>x</SUB>FeO<SUB>3</SUB> (x = 0.00, 0.05, and 0.10) belong to the rhombohedral (<I>R</I>3<I>c</I>) structure. Further increasing the Ho<SUP>3+</SUP> concentration in a BiFeO<SUB>3</SUB> (BFO) system revealed that Raman modes of Bi<SUB>1-x</SUB>Ho<SUB>x</SUB>FeO<SUB>3</SUB> (x = 0.15, 0.18 and 0.20) were assigned to an orthorhombic (<I>pnma</I>) structure, which is confirmed by the Rietveld analysis of X-ray diffraction data and TEM analysis. Ferroelectric studies show that the remnant polarization (P<SUB>r</SUB>) gradually decreases for Bi<SUB>1-x</SUB>Ho<SUB>x</SUB>FeO<SUB>3</SUB> (x = 0.15, 0.18, and 0.20), confirming the transformation from polar to non-polar systems. Magnetic measurement shows ferromagnetic behavior observed for Bi<SUB>1-x</SUB>Ho<SUB>x</SUB>FeO<SUB>3</SUB> (x = 0.10 and 0.20) samples. Further, the magneto-electric coupling is measured in terms of magneto-capacitance of Ho<SUP>3+</SUP>-substituted BiFeO<SUB>3</SUB> samples.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ho<SUP>3+</SUP> substituted BFO ceramics were synthesized by a solid-state reaction. </LI> <LI> Structural transformation from rhombohedral (<I>R</I>3<I>c</I>) to orthorhombic (<I>Pbnm</I>). </LI> <LI> Higher Ho<SUP>3+</SUP> substituted BFO is assigned orthorhombic (<I>Pbnm</I>) by Raman studies. </LI> <LI> Enhanced magneto-electric coupling observed in Ho<SUP>3+</SUP> substituted BFO samples. </LI> </UL> </P>
Structural, vibrational and band gap tunability of lead-free (1 − x)NaBiTO3-xBiMnO3 ceramics
Muneeswaran, Muniyandi,Kim, Dong Hun,Jung, Beon Sung,Park, Sung Heum,Choi, Byung Chun,Jeong, Jung Hyun,Chang, Seo Hyoung Chapman and Hall 2017 Journal of materials science Materials in electron Vol. No.
<P>We report the band gap tunability of (1 - x)Na0.5Bi0.5TiO3-xBiMnO(3) (x = 0.00, 0.05, 0.10 and 0.15) ceramics by a solid-state reaction method. X-ray diffraction (XRD) analysis confirmed the phase formation of rhombohedral structure with the space group of R3c. Rietveld refinement of XRD data revealed that the structural symmetry as a function of x composition. Raman analysis exhibited the vibrational phonon frequencies associated with Bi-O, Na-O, and TiO6 octahedral vibrations. The realized band gap energy variations (3.35-2.53 eV) suggesting that the synthesized ceramics materials are promising for photovoltaic and photocatalytic applications.</P>
Muniyandi Muneeswaran,김동훈,정번성,정중현,장재원,최병천 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.3
Single-phased [(1 − x) NBT-xBMO, x = 0.01 (NBTBM1), (1 − x) NBT-xBMO, x = 0.02 (NBTBM2), (1 − x) NBT-xBMO, x = 0.03 (NBTBM3), and (1 − x) NBT-xBMO, x = 0.04 (NBTBM4)] ceramic samples were prepared by using a solid-state method. X-ray diffraction analysis of the (1 − x) NBT-xBMO sample showed a rhombohedral structure and space group of R3c symmetry and confirmed the Rietveld refinement of the X-ray diffraction data. The micro-strain and the crystal sizes were calculated by using Williamson-Hall plots and experimentally verified with microstructural analyses. The in band-gap energy Eg varied from 3.28 to 3.17 eV for the (1 − x) NBT-xBMO ceramic samples. Furthermore, Raman spectra measured in the range from 100 to 1000 nm for the NBT-BMO powder samples showed new phonon modes and shifts to lower frequencies, which may be attributed to the incorporation of BMO into the NBT lattice.
Design of a Polarization Splitter Based on a Dual-core Hexagonal-shaped Photonic Crystal Fiber
Subramani Jegadeesan,Muneeswaran Dhamodaran,Maria Azees,Arunachalam Murugan 한국광학회 2019 Current Optics and Photonics Vol.3 No.4
In this paper, a microstructured, hexagonal-shaped dual-core photonic crystal fiber (PCF) is proposed. The proposed structure has specific optical properties to obtain high birefringence and short coupling length, for different values of structural parameters varied over a wide range of wavelength. The properties are analyzed using a solid core of silica material. The proposed structure is implemented as a polarization splitter with splitting length of 1.9 mm and a splitting ratio of -34.988 dB, at a wavelength of 1550 nm. The obtained bandwidth in one band gap of about 81 nm. The numerical analysis ensures that the performance of the proposed polarization splitter is better than that of existing ones.