The idea of this work was to investigate the dielectric and non-linear properties of the composite ceramic with the paraelectric phase (SrTiO3) fully isolated by the ferroelectric phase (BaTiO3). The ceramic composite with the 0-3 connectivity have been prepared by spark plasma sintering of the composite powders formed by SrTiO3@BaTiO3 core-shell particles. In order to prepare SrTiO3@BaTiO3 core-shell particles we have used a multistep process: (i) synthesis of the SrTiO3 cores; (ii) coating the SrTiO3 cores with a shell of amorphous TiO2; (iii) transformation of SrTiO3@TiO2 core-shell particles into SrTiO3@BaTiO3 core-shell particles. The phase formation and morphologies have been investigated by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dielectric properties measure from (25-200)°C temperature and in a broad frequency range (20Hz- 1GHz) were investigated and discussed. From temperature dependence on dielectric permittivity it was observed a giant relaxation effect, after reoxidation process, with a strong shift of Tm with frequency (to above ~80°C when f?(1, 106)Hz), which cannot be related to the relaxor state (Fig. 1(a)). The observed relaxation is an extrinsic effect most probably related to the oxygen deficiency and not to the relaxor behaviour of this system. The complex impedance showed that only one single component in the complex impedance plot found, after first step of reoxidation. Thus, the annealing process allowed the homogenization of the oxygen level within the ceramic grains, but dielectric relaxation (?') proposed the existence of 2 regions with different oxygen vacancies concentration - boundary/bulk or other effects. The frequency and temperature dependence of dielectric characteristics have been also investigated and discussed in correlation with the microstructural data perform by TEM and SEM analysis. The non-linear investigation revealed a strong variation of permittivity vs. electrical field (Fig. 1(b)). The obtained results can be correlated with the peculiar microstructure of the present sample.
Dielectric and non-linear properties of SrTiO3@BaTiO3 core-shell ceramic
M T Buscaglia;V Buscaglia;
2014
Abstract
The idea of this work was to investigate the dielectric and non-linear properties of the composite ceramic with the paraelectric phase (SrTiO3) fully isolated by the ferroelectric phase (BaTiO3). The ceramic composite with the 0-3 connectivity have been prepared by spark plasma sintering of the composite powders formed by SrTiO3@BaTiO3 core-shell particles. In order to prepare SrTiO3@BaTiO3 core-shell particles we have used a multistep process: (i) synthesis of the SrTiO3 cores; (ii) coating the SrTiO3 cores with a shell of amorphous TiO2; (iii) transformation of SrTiO3@TiO2 core-shell particles into SrTiO3@BaTiO3 core-shell particles. The phase formation and morphologies have been investigated by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dielectric properties measure from (25-200)°C temperature and in a broad frequency range (20Hz- 1GHz) were investigated and discussed. From temperature dependence on dielectric permittivity it was observed a giant relaxation effect, after reoxidation process, with a strong shift of Tm with frequency (to above ~80°C when f?(1, 106)Hz), which cannot be related to the relaxor state (Fig. 1(a)). The observed relaxation is an extrinsic effect most probably related to the oxygen deficiency and not to the relaxor behaviour of this system. The complex impedance showed that only one single component in the complex impedance plot found, after first step of reoxidation. Thus, the annealing process allowed the homogenization of the oxygen level within the ceramic grains, but dielectric relaxation (?') proposed the existence of 2 regions with different oxygen vacancies concentration - boundary/bulk or other effects. The frequency and temperature dependence of dielectric characteristics have been also investigated and discussed in correlation with the microstructural data perform by TEM and SEM analysis. The non-linear investigation revealed a strong variation of permittivity vs. electrical field (Fig. 1(b)). The obtained results can be correlated with the peculiar microstructure of the present sample.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
