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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:56 |
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Conference: Bucharest University Faculty of Physics 2012 Meeting
Section: Solid State Physics and Materials Science
Title:
Dielectric properties of nanostructured BNT-BT0.08 lead free ceramics
Authors:
Stefania BUSUIOC(1), Aida APAZ(1), M. CERNEA(2), S. VULPE(1), C. BERBECARU(1)
Affiliation:
(1) University of Bucharest, Faculty of Physics, 70709, Bucharest, Romania
(2) National Institute of Materials Physics, P.O. Box MG-7, Bucharest-Magurele, 077125, Romania
E-mail
busuioc_stefania@yahoo.com, apazaida@yahoo.com, mcernea@infim.ro, vulpesilviu@psg.unibuc.ro, berbecaru2ciceron@yahoo.com
Keywords:
sol-gel (Bi0.5Na0.5)TiO3 doped with BaTiO3, Spark Plasma Sintering (SPS), dielectric properties
Abstract:
Pb(Zr,Ti)O3 or PZT ceramics are widely used for piezoelectric applications. Because of the lead toxicity some other materials are investigated to replace PZT. From this point of view (Bi0.5Na0.5)TiO3-BaTiO3, (BNT-BT) based ceramics is a promising alternative. At room temperature perovskite BNT ceramics are rhombohedral. Around 320 deg. C the structure changes to a tetragonal one by a diffuse phase transition. Strong frequency dispersion places these ceramics in the relaxors category. BNT material shows ferroelectric properties with high coercive field Ec = 73 kV/cm, large values of remnant polarization Pr = 38 C/cm^2, and high values of leakage current making difficult to pole the structure. Poor piezoelectric properties of BNT do not recommend it to be directly used. Piezoelectric properties of BNT ceramics could be improved by dopage, around the morphotropic phase boundaries. BNT doped with 8 mol % BT powder (BNT-BT0.08), were prepared by sol-gel method, compacted and sintered by Spark Plasma Sintering (SPS) process. Starting from sol-gel BNT-BT0.08 nanopowder with 30 nm average particles size, were obtained at 850 °C SPS sintering temperature ceramics with density of about 98 % of the theoretical value. The average grain size of the resulting ceramics was 80 nm. The influence of SPS sintering temperatures on the densification of BNT-BT0.08 ceramic was also investigated. The BNT-BT0.08 ceramic sample obtained by SPS method shows good dielectric properties in the 40–10^6 Hz frequency and 25–400 deg. C temperature ranges.
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