• Applied Microscopy
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• v.32 no.3
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• pp.257-263
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• 2002

Microstructural investigations of $(Li_{1/2}Pr_{1/2})TiO_3$ (LPT) complex perovskite compounds were carried out using X-ray diffractometry and transmission electron microscopy. LPT has not only the ordering of A-site cation deficiencies but also has the antiphase and inphase tilting of oxygen octahedron and the antiparallel shift of cations. Both the antiphase boundaries and the ferroelastic domains are present in the microstructure. Spinodal decomposition is found in the microstructure. The measured dielectric properties were ${\varepsilon}_r=84.6,\;Q\;{\Large f}_o=776\;GHz,\;{\tau}_{f}=-233.66ppm/^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.35 no.11
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• pp.1182-1189
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• 1998

Crystal structure and structural stability of needle-shaped maghemite(${\gamma}$-{{{{ { {Fe }_{2 }O }_{3 } }}) have been studied by the computation and estimation of lattice energies interionic distances and site potentials. The refined struc-tures analyzed with cubic system(space group P4332) and tetragonal system(space group P4332) were used for these computations. The lattice energy of tetragonal system is -143.10eV/molecule. The maghemite structure with tetragonal system is more stable than that with cubic system. The ordering energy of the FE and cation vacancy within the octahedral site the 4b site of the structure with cubic system(space group P4332) is -0.95eV/molecule but this Fe has larger interionic distance and is very unstable.

• Journal of Magnetics
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• v.20 no.4
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• pp.331-335
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• 2015

The ferromagnetic and electronic structure for the $Al_xGa_{1-x}P$ and Mn-doped $AlGaP_2$ was studied by using the self-consistent full-potential linear muffin-tin orbital method. The lattice parameters of un-doped $Al_xGa_{1-x}P$ (x = 0.25, 0.5, and 0.75) were optimized. The band-structure and the density of states of Mn-doped $AlGaP_2$ with or without the vacancy were investigated in detail. The P-3p states at the Fermi level dominate rather than the other states. Thus a strong interaction between the Mn-3d and P-3p states is formed. The ferromagnetic ordering of dopant Mn with high magnetic moment is induced due to the (Mn-3d)-(P-3p)-(Mn-3d) hybridization, which is attributed by the partially filled P-3p bands. The holes are mediated with keeping their 3d-characters, therefore the ferromagnetic state is stabilized by this double-exchange mechanism.

• Journal of the Korean Ceramic Society
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• v.44 no.12
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• pp.655-659
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• 2007

Zirconia polycrystals co-doped with x mol% CaO and (10-x) mol% $Y_2O_3$ were prepared by solid state reaction method. The compositions were chosen for nominally the same oxygen vacancy concentration of 5 mol%. X-ray diffraction patterns indicated the formation of cubic zirconia by heat treatment at $1600^{\circ}C$. Impedance spectroscopy was applied to deconvolute the bulk and grain boundary response. Electrical conductivity was measured using the complex impedance technique from 516 to 874 K in air. Maximum conductivity was exhibited by the composition with equal amounts of CaO and $Y_2O_3$, which may be ascribed to the smaller degree of defect-interactions in that composition due to the competition of different ordering schemes between the two systems. When compared to the composition containing $Y_2O_3$ only, co-doping of CaO increases the grain boundary resistance considerably. The activation energy of grain and grain boundary conductivity was 1.1 eV and 1.2 eV, respectively, with no appreciable dependence on dopant compositions.