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Solidification Behaviour of Binary Organic Eutectics and 1:2 Addition Compounds
Rai, U. S.,George, Santhi Korean Chemical Society 1994 Bulletin of the Korean Chemical Society Vol.15 No.3
Due to possibility of visual observation of phase transformations and processes during solidification, the transparent binary alloy models are important in materials and metallurgical sciences. As such, phase diagram, linear velocity of crystallization, microstructure and spectral behaviour of binary organic systems of benzidine with resorcinol and catechol involving formation of addition compound with congruent melting point have been studied. While their phase diagrams show the formation of two eutectics and a 1:2 (B:RC, B:CT) addition compound in each case, the crystallization data obey the Hillig-Turnbull equation. The microstructural investigations give the characteristic morphology of the eutectics and the addition compounds, the spectral studies suggest intermolecular hydrogen bonding between two components forming the molecular complex.
SINGHLAXMAN,U. S. Rai,Alok Kumar Rai,K. D. Mandal,이선영 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.1
CaCu2.90Zn0.10Ti4O12 ceramic was synthesized by a novel semi-wet route and calcined at 800°C in air for 8 h. The obtained powder was divided into three parts and sintered in air at 950°C for 6 h, 8 h, and 12 h,separately. XRD results confirmed the single phase formation of all the sintered samples with similar cubic structure of CaCu3Ti4O12 (CCTO). Scanning electron micrographs of the CaCu2.9Zn0.1Ti4O12 ceramic sintered for 6 h shows bimodal grain size distribution. Increasing the sintering time significantly promotes the grain growth and microstructural densification. The sintering duration was found to have tremendous influence on microstructure and dielectric properties of CaCu2.90Zn0.10Ti4O12 ceramic. The CaCu2.9Zn0.1Ti4O12 ceramic sintered for 12 h exhibited high dielectric constant εr ~ 5971 at 1 kHz and room temperature. It is found that εr is independent at high frequency and weakly dependent on temperature.
Singh, L.,Yadava, S. S.,Sin, B. C.,Rai, U. S.,Mandal, K. D.,Lee, Y. Springer Science + Business Media 2016 Journal of electronic materials Vol.45 No.6
<P>The dielectric and ferroelectric characteristics of Bi0.5Na0.5TiO3 (BNT), CaCu3Ti4O12 (CCTO), and 0.5Bi(0.5)Na(0.5)TiO(3)-0.5CaCu(3)Ti(4)O(12) (BNT/CCTO) ceramics are compared. X-ray diffraction patterns confirmed the formation of single phase of all the ceramics after sintering at 950A degrees C for 15 h. Scanning electron microscopy images of the sintered ceramics reveal average grain sizes in the range from 200 nm to 2.5 mu m. Energy-dispersive x-ray mapping and x-ray photoelectron spectroscopy show the presence of the elements Bi, Na, Ca, Cu, Ti, and O with uniform distribution in the ceramics. BNT/CCTO exhibits high dielectric constant (epsilon (r) similar to 6.9 x 10(4)) compared with BNT (epsilon (r) similar to 0.13 x 10(4)) and CCTO (epsilon (r) similar to 1.68 x 10(4)) ceramics at 1 kHz and 503 K. The high dielectric constant of BNT/CCTO compared with BNT and CCTO is associated with a major contribution from grain boundaries, as confirmed by impedance and modulus analyses. The P-E hysteresis loop of all the ceramics measured at room temperature and 50A degrees C exhibited typical ferroelectric nature. The remanent polarization (P (r)) of BNT (1.58 mu C/cm(2)) and CCTO (0.654 mu C/cm(2)) ceramics are higher than that of BNT/CCTO (0.267 mu C/cm(2)) ceramic.</P>