Etude des céramiques diélectriques du type BaTiO3-CaTiO3 Influence de différentes additions
Barama, S. E.
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In this work we are concerned with the preparation and characterisation of BaTiO3 - CaTiO3 –B2O3 nonlinear dielectric materials. Samples of (1-x) BaTiO3 +xCaTiO3 +y B2O3 type (with x=0.3; 0.7 and 0.01≤y≤0.03) were elaborated by sintering at various temperatures (1200, 1250, 1300 and 1350°C respectively) during 03h. The obtained results showed an improvement in the relative density in the case of samples containing 1% B2O3. At the opposite, the relative density of the sintered samples decreases for higher B2O3 percentage probably in relation with the apparition of liquid phase. For example, in the case of samples containing 30 % mol. in CT and sintered 1300°C, the addition of 1% mol. in B2O3 leads to an increasing in the relative density from 65 to 93% and from 78 to 95% in the case 1350°C sintering temperature. On the other hand, the obtained results reveal an increase in the relative density with sintering temperature for all B2O3 percentage. X-rays diffraction analyses carried out with different sintered samples showed the formation of both BT and CT solid solutions, and a non identified phase. The proportion of the farmer phase increases as a function of B2O3 addition. Dielectric measurements carried out with samples containing 30% CT showed that the relative permittivity (εr) increases as function of BO additions in the case of samples sintered at 1200°C. In the case of higher sintering temperatures, maximum of permittivity is obtained with 1% BO. In addition, εr evolution with the temperature reveals ferro para transformation in all considered samples. In the second part, a new simple method was used, saving time and effort for the preparation of the BCT. This method is the hydrothermal, a series of BCT samples were prepared without and with addition of F2O3. We used in autoclave Ti metal plates with BaOH, CaO powders in addition to F2O3 Chloride under temperature conditions of 200 ° C. for different periods of time. This allowed us to have the BCT compound. Following the addition of Iron Chloride, we noticed a change in the structure approved by the Raman, DRX and XPS analyzes. This latter confirms the presence of all the elements used in the synthesis of the composit.
- Doctorat (Physique)