Synthesis, Structural and Electrical Properties of BNT-BTCe@SiO2 Core-Shell Heterostructure

The influence of SiO2 layer in a core-shell BNT-BTCe@SiO2 heterostructure on the electrical properties of the BNT-BTCe core ceramic was investigated. The core-shell composite was prepared by coating BNT-BTCe powder with silica layer by a chemical process. BNT-BTCe grain-core was a solid solution of (Bi0.5Na0.5)TiO3 (BNT) and Ba0.95Ce0.05TiO3 (BTCe) with 92: 8 molar ratio. The thickness of the amorphous silica shell was about 128 nm and the size of the grain core was about 250 nm. The structure, microstructure, dielectric, ferroelectric and piezoelectric properties of BNT-BTCe@SiO2 core-shell powder and sintered ceramic were investigated and compared with those of the BNT-BTCe base material. We found that the values of permittivity (epsilon(r)) and dielectric losses of core-shell ceramic are lower and higher, respectively, than those of BNT-BTCe ceramic indicating that the SiO2 does not improve the dielectric properties of BNT-BTCe ceramic. For the BNT-BTCe@SiO2 composite, the silica layer leads to the increase of diffuseness degree of the phase transition and to a better ferroelectric relaxor. The sintered BNT-BTCe@SiO2 heterostructure shows higher remnant polarization P-r, higher coercive field E-c and higher piezoelectric constants (k(t), d(33), g(33), c(33)(E) and S-11(E)) than BNT-BTCe ceramic. The results of our study suggest that BNT-BTCe@SiO2 core-shell material could be interesting for applications in the ferroelectric and piezoelectric domains.