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Abdelaziz Salhi,Salaheddine Sayouri,Lahoucine Hajji,TajEddine Lamcharfi 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.12
Nanocrystalline barium titanate (BT) was synthesized by the sol gel method. The dry gel obtained was first treated in themicrowave (MW) and then calcined at different temperatures. A pure tetragonal phase was obtained under heat treatmentat 750 oC which is a relatively low temperature. SEM image reveals a fairly dense and uniform microstructure. Dielectricmeasurements performed on the sintered BaTiO3 sample at 1200 oC revealed the presence of the resonance phenomenon atfrequencies lower than 2 MHz and the existence of a weak positive temperature coefficient of resistivity (PTCR) just abovethe Curie temperature. Electric impedance analysis shows the predominance of the grain boundary (gb) contribution andenables determination of activation energies of the gb and the bulk effect and their relative capacitance and resistanceelements.
Abdelhak El Ghandouri,Salaheddine Sayouri,TajEddine Lamcharfi,Lahoucine Hajji 한양대학교 세라믹연구소 2018 Journal of Ceramic Processing Research Vol.19 No.2
Structural, dielectric and piezoelectric properties of nanopowders of pure and strontium-doped BaTiO3 (Ba1-xSrx)TiO3 (x =0.00; 0.10; 0.20; 0.30 and 0.40), synthesized by the sol gel process, have been investigated. The samples crystallize in the pureperovskite structure and transform from tetragonal to pseudocubic under doping with Sr. The calculated average crystallitesize was about 30 nm. Dielectric parameters (dielectric permittivity and losses) were determined. Sr doping gives rise to adecrease of the ferro-to-paraelctric transition temperature and to an enhancement of the Positive Temperature Coefficient ofResistivity (PTCR). Piezoelectric parameters were also determined and their thermal behavior investigated.