scholarly journals Dielectric Anisotropy in Partially Grain-Oriented Bi2VO5.5Ceramics

1995 ◽  
Vol 18 (3) ◽  
pp. 137-144 ◽  
Author(s):  
K. V. R. Prasad ◽  
K. B. R. Varma
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Grain Orientation ◽  
Hysteresis Loops ◽  
Dielectric Constants ◽  
Dielectric Anisotropy ◽  
Ferroelectric Domains ◽  
Ferroelectric Hysteresis ◽  
Microstructural Studies ◽  
Scanning Electron

Ceramics obtained from quenching melts of prereacted polycrystalline Bi2V5.5exhibit grain orientation (~ 55%). Microstructural studies carried out using scanning electron microscopy (SEM) on subsequently annealed ceramics show ferroelectric domains. These post-annealed ceramics possess dielectric anisotropies of about 1:1.2 at 300 K and 1:4.3 in the vicinity of the Curie temperature (~ 730 K) between the directions parallel and perpendicular to the quenching direction. The dielectric constants of the samples, obtained by quenching the melts, are higher than that of the post-annealed ceramics. Electrically poled and thermally cycled samples of both as-quenched and post-annealed exhibit ferroelectric hysteresis loops at 300 K.

Some Physical Properties of Suspendable Superconducting 123-Ag Composites

1989 ◽  
Vol 169 ◽  
Author(s):  
C. Y. Huang ◽  
H. H. Tai ◽  
Y. D. Yao ◽  
T. J. Li ◽  
M. K. Wu
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Field Dependence ◽  
High Field ◽  
Polarized Light ◽  
Hysteresis Loops ◽  
Residual Magnetization ◽  
Superconducting Transition ◽  
Phase Slippage ◽  
Scanning Electron

AbstractWe have measured the M-H hysteresis loops of n YBa2Cu3Oy: Ag (n = 3,5, and 7), and 3RBa2Cu3Oy:Ag (R = rare earth) as a function of temperature. We have found that the residual magnetization and, hence, pinning, is strong and is independent of n and R, but dependent on the metallurgy. The giant creep rates have been measured and are greater than those of pure 123 samples. Scanning electron microscopy and polarized light microscopy have shown that the presence of silver gives rise to the growth of large grains (~1 mm) in the 123-Ag samples. The field dependence of the critical current density is not strong at high field. We have also measured the resistance in field up to 200 kOe. The resistance remains zero even at 80 K and 200 kOe. The field dependence of the superconducting transition is discussed in terms of phase slippage.

MICROSTRUCTURAL STUDIES OF SUPERCONDUCTING 3EuBa2Cu3Oy:AgO AND 3GdBa2Cu3Oy:AgO COMPOSITES

1989 ◽  
Vol 03 (11) ◽  
pp. 877-885
Author(s):  
C.Y. HUANG ◽  
H.H. TAI ◽  
M.K. WU
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Light Microscopy ◽  
Silver Particle ◽  
Polarized Light ◽  
Energy Dispersive ◽  
X Ray ◽  
Grain Formation ◽  
Microstructural Studies ◽  
Scanning Electron

Scanning electron microscopy, energy dispersive X-ray spectroscopy, and polarized light microscopy have shown that the addition of AgO to the E uBa 2 Cu 3 O y and GdBa 2 Cu 3 O y systems results in the growth of very large grains. Distribution of silver particle appears to influence the grain formation and growth in the superconducting composites.

IMPEDANCE SPECTROSCOPY (IS), XRD AND SEM OF OXIDE-ADDED Si3N4

2002 ◽  
Vol 16 (14) ◽  
pp. 525-537
Author(s):  
SAADAT. A. SIDDIQI ◽  
NASIR A. KHAN ◽  
M. SABIEH ANWAR
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Impedance Spectroscopy ◽  
Ceramic Materials ◽  
Dielectric Constants ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nyquist Plots ◽  
Non Destructive ◽  
Scanning Electron

Impedance spectroscopy (IS) is a non-destructive technique used for obtaining valuable information about bulk conductivities, dielectric constants, phase composition and grain boundaries of important ceramic materials, amongst many others. We obtained Nyquist plots for four different hot-pressed Si 3 N 4 samples in two different frequency regimes: 1 Hz to 30 MHz and 1 kHz to 100 kHz. The information obtained was compared against results from scanning electron microscopy (SEM) and X-ray diffraction (XRD). The limitations of the frequency response techniques are also discussed.

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