Dielectric and magnetic properties of sol-gel-derived lead iron niobate ceramics
- Department of Physics, University of Puerto Rico, San Juan, 00931-3343 (Puerto Rico)
In this work, we report the synthesis of sol-gel-derived lead iron niobate [Pb{sub 1.10}(Fe{sub 0.5}Nb{sub 0.5})O{sub 3}] (PFN) powders and sintered ceramics. The PFN powders were calcined at (T{sub a}), 973, 1073, 1173, 1273, and 1373 K for 3 h in air. As envisaged from x-ray-diffraction analyses, PFN powder calcined at 1173 K was crystallized into pure monoclinic perovskite phase whereas powders calcined at all other temperatures had varied amounts of retained pyrochlore (Pb{sub 3}Nb{sub 4}O{sub 13}) phase coexisted with dominant monoclinic perovskite phase. The PFN pellet (prepared using the phase pure powder calcined at 1173 K) sintered at 1373 K for 4 h in air also had a minute quantity of retained pyrochlore phase coexisting with desired perovskite phase. From the temperature dependence of measured capacitance and loss tangent at different frequencies, the ferroelectric to paraelectric phase-transition temperature of PFN ceramics was observed at T{sub c}{approx_equal}370 K. The diffused nature of this transition and high dielectric constant of PFN is related to the cation disorder at the B site of A(B{sub I}{sup +3}B{sub II}{sup +5})O{sub 3} lattice. For PFN powders, calcined at different temperatures, the temperature dependence of the magnetic susceptibility ({chi}) was measured in a temperature range of 2-360 K, whereas the magnetic hysteresis loops and electron magnetic resonance (EMR) spectra were measured at room temperature. Room-temperature ferromagnetism is observed in all the calcined powder samples and it was found that the magnetization increases with the increase in calcination temperature (T{sub a}). The symmetric EMR line shape with g{approx_equal}2.01 observed in all calcined samples was identified to be due to Fe{sup 3+} ions. It is suggested that the observed weak ferromagnetism, which increases with an increase in T{sub a}, may be due to canting of the Fe{sup 3+} spins. These observations suggest PFN to be a very attractive single-phase ferroelectric/ferromagnetic material for room-temperature applications.
- OSTI ID:
- 20787800
- Journal Information:
- Journal of Applied Physics, Vol. 99, Issue 2; Other Information: DOI: 10.1063/1.2158131; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CALCINATION
CERAMICS
CRYSTALLIZATION
CURIE POINT
FERROELECTRIC MATERIALS
FERROMAGNETIC MATERIALS
FERROMAGNETISM
IRON COMPOUNDS
IRON IONS
LEAD COMPOUNDS
MAGNETIC SUSCEPTIBILITY
MONOCLINIC LATTICES
NIOBATES
PERMITTIVITY
PEROVSKITE
PYROCHLORE
SOL-GEL PROCESS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0273-0400 K
X-RAY DIFFRACTION