Browsing by Author "Valente, M A"

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STRUCTURAL, CONDUCTIVITY AND DFT STUDIES OF L-HISTIDINIUM PHOSPHITE – FERROELECTRIC PHOSPHITE SINGLE CRYSTAL
(Elsevier, 2021-08) Shanmuga Sundari, S; Mano Priya, A; Durairajan, A; Valente, M A
L-Histidinium phosphite [C6N3O2H10]+. [HPO3H]- abbreviated as HPI, is a semi-organic nonlinear optical material. In the present work HPI crystals were grown from the aqueous solution of HPI by slow evaporation technique. Single crystal XRD (SXRD) reveals that the resulting crystals predominantly exhibit monoclinic structure with space group P21. Sharp and well-defined peaks of the powder XRD pattern attested the good crystallinity of HPI and the pattern is in agreement with SXRD results. The different modes of vibrations of molecular groups and functional groups present in the HPI crystal was investigated using IR spectra. It is evident from the UV–Vis spectrum that HPI is transparent in the examined frequency regime. The TG-DTA studies ascertain that the crystal is thermal stable till 230 °C. A.C. and D.C. conduction mechanism in the grown crystals were studied from 119 K to 380 K for 1 kHz to 1 MHz frequency range. The pattern suggests that there is ferroelectric to paraelectric transition at 270 K. This transition temperature is higher than the glycine phosphite crystals. Detailed insight about the conduction mechanism in HPI crystals was analyzed by complex impedance and modulus studies. Density functional theory was applied to know in detail about the structure and non-linear optical characteristics of the grown crystal and it attested that HPI is NLO active at room temperature.
STUDY ON GROWTH, OPTICAL AND DIELECTRIC PROPERTIES OF ‘ND’ DOPED NBT-BT (0.94(NA0.5BI0.5TIO3)-0.06BATIO3) RELAXOR FERROELECTRIC SINGLE CRYSTALS
(Springer Link, 2022-04-01) Shanmuga Sundari, Sankaran; Dhanasekaran, R; Binay, Kumar; Durairajan, A; Valente, M A; Devaraj Stephen, L
The present work describes the effect of Neodymium (Nd) in the NBT-BT (0.94Na0.5Bi0.5TiO3-0.06BaTiO3 (NBT-BT (94/06)) + xNd (x = 0, 0.4, 0.6, 0.8, 1.0 wt%)) crystal grown by flux method. As the concentration of the Nd increases beyond 0.4 wt%, homogeneity of the solution is lost and the multinucleation was observed. Color of the crystal changed from yellow to muddy green and size of the crystals were reduced due to the incorporation of Nd in NBT-BT. Nd completely diffused into the NBT-BT lattice, hence no secondary phase formation was observed in XRD. But the peaks were shifted towards the higher angle side due to the shrinkage of NBT-BT lattice. Optical properties of the crystals are studied using UV–visible and photoluminescence spectra. Except 0.4 wt% of Nd, for all other concentration emission at 1064 nm was observed in the PL spectra. Effect of Nd in dielectric constant and the relaxor properties are discussed in detail.
STUDY ON GROWTH, OPTICAL AND DIELECTRIC PROPERTIES OF ‘ND’ DOPED NBT-BT (0.94(NA0.5BI0.5TIO3)-0.06BATIO3) RELAXOR FERROELECTRIC SINGLE CRYSTALS
(SpringerLink, 2022-04-01) Shanmuga Sundari, Sankaran; Dhanasekaran, R; Binay, Kumar; Durairajan., A; Valente, M A; Devaraj, Stephen. L
The present work describes the effect of Neodymium (Nd) in the NBT-BT (0.94Na0.5Bi0.5TiO3-0.06BaTiO3 (NBT-BT (94/06)) + xNd (x = 0, 0.4, 0.6, 0.8, 1.0 wt%)) crystal grown by flux method. As the concentration of the Nd increases beyond 0.4 wt%, homogeneity of the solution is lost and the multinucleation was observed. Color of the crystal changed from yellow to muddy green and size of the crystals were reduced due to the incorporation of Nd in NBT-BT. Nd completely diffused into the NBT-BT lattice, hence no secondary phase formation was observed in XRD. But the peaks were shifted towards the higher angle side due to the shrinkage of NBT-BT lattice. Optical properties of the crystals are studied using UV–visible and photoluminescence spectra. Except 0.4 wt% of Nd, for all other concentration emission at 1064 nm was observed in the PL spectra. Effect of Nd in dielectric constant and the relaxor properties are discussed in detail.