(Pb(0.8)La(0.2))(Mg(0.4)Nb(0.6))O(3) relaxor ceramics have been prepared by columbite method by using (i) MgO and (ii)(MgCO(3))(4)center dot Mg(OH)(2)center dot 4H(2)O precursors (denoted as PLMN1 and PLMN2 respectively). The dielectric data show relaxor behaviour in the frequency range of 10 Hz to 1 MHz, with dielectric constant values in the range of 310-350 for PLMN1 and 240-260 for PLMN2 and a permittivity maxima at the temperature T(m)=179 K and T(m)=174K, respectively (for f=1 MHz). The Raman spectra proved the stability of the nanopolar order far above T, as observed in many Pb-based relaxors. This is demonstrated by the existence of some modes (at similar to 300, 500 and 780 cm(-1)) up to around 773K. Anomalies of some Raman modes (integrated intensity and FWHM) have been found in the range of T(m), proving the phase transition from pseudo-cubic relaxor to cubic paraelectric state, where the stability of the vibration modes is affected by the fluctuations associated to the phase transitions. (C) 2010 Elsevier B.V. All rights reserved.
Raman investigation and functional characterization of (Pb(0.8)La(0.2))(Mg(0.4)Nb(0.6))O(3) ceramics prepared by the columbite method
CARNASCIALI, MARIA;
2010-01-01
Abstract
(Pb(0.8)La(0.2))(Mg(0.4)Nb(0.6))O(3) relaxor ceramics have been prepared by columbite method by using (i) MgO and (ii)(MgCO(3))(4)center dot Mg(OH)(2)center dot 4H(2)O precursors (denoted as PLMN1 and PLMN2 respectively). The dielectric data show relaxor behaviour in the frequency range of 10 Hz to 1 MHz, with dielectric constant values in the range of 310-350 for PLMN1 and 240-260 for PLMN2 and a permittivity maxima at the temperature T(m)=179 K and T(m)=174K, respectively (for f=1 MHz). The Raman spectra proved the stability of the nanopolar order far above T, as observed in many Pb-based relaxors. This is demonstrated by the existence of some modes (at similar to 300, 500 and 780 cm(-1)) up to around 773K. Anomalies of some Raman modes (integrated intensity and FWHM) have been found in the range of T(m), proving the phase transition from pseudo-cubic relaxor to cubic paraelectric state, where the stability of the vibration modes is affected by the fluctuations associated to the phase transitions. (C) 2010 Elsevier B.V. All rights reserved.
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