Enhanced magnetoelectric response of cofired ceramic layered composites by adjusting the grain boundary conductivity of the magnetostrictive component

ABSTRACTIonic conductivities of solid CeO2:Y203 electrolytes were systematically investigated as a function of dopant concentration and sintering temperatures. The highest lattice conductivity occurred at 6–8% dopant concentration, and maximum grain boundary conductivity was observed at 10% dopant concentration. The sintering temperature was found to have a significant effect on the conductivities of the pellets. The samples sintered at lower temperatures (T≤140°C) showed higher grain boundary conductivity than those sintered at 150°C; this was found to be related to size-dependent-impurity segregation and precipitation at grain boundaries. The grain boundary conductivities as related to the microstructure are discussed by adopting different grain boundary models. Solute segregation and oxygen depletion at grain boundaries, which have been suggested to be responsible for the grain boundary resistivities in these samples, were examined by a microanalytical technique for small-grain-size samples.

Download Full-text

Conductivity of Grains and Grain Boundaries in Polycrystalline Heteropoly Acid Salts

Materials Science Forum ◽

10.4028/www.scientific.net/msf.494.101 ◽

2005 ◽

Vol 494 ◽

pp. 101-106

Author(s):

B. Škipina ◽

T. Čajkovski ◽

M. Davidović ◽

D. Čajkovski ◽

V. Likar-Smiljanić ◽

...

Keyword(s):

Impedance Spectroscopy ◽

Grain Boundary ◽

Grain Boundaries ◽

Heteropoly Acid ◽

Tungstophosphoric Acid ◽

Heteropoly Acids ◽

Relaxation Phenomena ◽

Frequency Range ◽

Boundary Conductivity ◽

Bivalent Ions

In our previous work we investigated the conductivity and dielectric relaxation phenomena in heteropoly acids and their salts. In this work, we have studied the conductivity of grains and grain boundaries in compressed powders of 12-tungstophosphoric acid (WPA) salts with univalent and bivalent ions. The method of impedance spectroscopy has been employed in the frequency range from 5 Hz to 500 kHz. We obtained grains and grain boundaries conductivities as well as corresponding activation energies. Grain conductivity in all investigated salts is always higher than the grain boundary conductivity.

Download Full-text

Effect of Annealing Temperature on the Li\(^{ + }\) Ionic Conductivity of La\(_{0.67 - x}\)Li\(_{3x}\)TiO\(_{3 }\)

Communications in Physics ◽

10.15625/0868-3166/19/4/6409 ◽

2009 ◽

Vol 19 (4) ◽

pp. 235-242

Author(s):

Le Dinh Trong ◽

Pham Duy Long ◽

Nguyen Nang Dinh

Keyword(s):

High Temperature ◽

Ionic Conductivity ◽

Thermal Treatment ◽

Grain Boundary ◽

Room Temperature ◽

Annealing Temperature ◽

Boundary Conductivity ◽

Impedance Measurements ◽

Post Annealing ◽

Reactive Milling

Perovskite La0.67-xLi3xTiO3 with x = 0.10, 0.11, 0.12 and 0.13 were firstly annealed at 800 oC then treated by reactive milling, followed by post-annealing at temperatures from 1100 to 1200oC. The crystalline structure of grain and grain-boundary were characterized by XRD and SEM. The impedance measurements showed that nanocrystalline La0.67-xLi3xTiO3 after being annealed at 1150 oC possessed a grain conductivity as high as 1.3×10-3 S.cm-1. The grain-boundary conductivity was enhanced one order in magnitude after annealing at temperature higher 1100oC and consists of 5.8×10-5 S.cm-1. The results have also showed the limitation of the adiabatic thermal treatment for the improvement of the grain-boundary conductivity and suggested the way to overcome the limitation by rapidly cooling the samples from the high temperature to room temperature.

Download Full-text