FIELD-INDUCED PHASE TRANSITION AND RELAXOR CHARACTER IN SUBMICRON STRUCTURED LEAD-FREE ( Bi 0.5 Na 0.5 ) 0.94 Ba 0.06 TiO3 PIEZOCERAMICS AT THE MORPHOTROPIC PHASE BOUNDARY
Submicron-structured (Bi0.5Na0.5)0.94Ba0.06TiO3 ceramics (<G> < 720nm) from nanopowders were studied. The real part of the optimum room temperature set of piezoelectric coefficients obtained from resonances of the BNBT6 dense ceramic disks and shear plates (d31=(-37+1.33i)pC.N-1, d15=(158.3...
| Autores: | , , , , |
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| Formato: | artículo |
| Fecha de publicación: | 2011 |
| País: | España |
| Recursos: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/40776 |
| Acesso em linha: | http://hdl.handle.net/10261/40776 |
| Access Level: | acceso abierto |
| Palavra-chave: | Phase Transition Transición Piezoelectricity Piezoelectricidad Ferroelectricity Ferroelectricidad Lead-Free Verde Bismuth Bismuto Sodium Sodio Barium Bario Titanate Titanato Relaxor Dielectric Permitivity Permitividad Dieléctrica |
| Resumo: | Submicron-structured (Bi0.5Na0.5)0.94Ba0.06TiO3 ceramics (<G> < 720nm) from nanopowders were studied. The real part of the optimum room temperature set of piezoelectric coefficients obtained from resonances of the BNBT6 dense ceramic disks and shear plates (d31=(-37+1.33i)pC.N-1, d15=(158.3 -8.31i) pC.N-1, kt= 40.4%, kp=26.8% and k15=40.2% ) and d33=148 pC.N-1 can be compared with the reported properties for coarse-grained ceramics. Shear resonance of thickness poled plates is observed at T=140ºC. Permittivity vs. temperature curves of poled samples show relaxor character up to Ti=230ºC on heating and Ti=210ºC on cooling of the depoled samples. The phase transition from the room temperature ferroelectric (FE) to a Low Temperature Non-Polar at Zero Field (LTNPZF) phase can be observed as a sharp jump in eps´33(T)curves or, as the degree of poling decreases, as a soft change of slope of the curves at T(FE-LTNPZF)= Td = 100ºC. This dielectric anomaly is not observed on cooling of depoled samples, as the FE phase is field-induced. The observed macroscopic piezoelectric activity above Td is a consequence of the coexistence of nanoregions of the FE phase in the interval between T(FE-LTNPZF) and Ti. |
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