New materials and processes for the manufacturing of ceramics presenting colossal values of permittivity

Due to their potential application in microelectronics, high dielectric constant materials, (epsiv'
_r
> 10 000), are very attractive. Among them, there has been recently a considerable interest for various perovskite oxides like calcium copper titanate CaCu
₃
Ti
₄
O
₁₂
(CCT hereafter) or lanthanum doped barium titanate (Bai
_1-x
La
_x
Ti
_1-x/4
O
₃
(0 les x les 0.138) (La doped BT)). These materials may exhibit, when processed in a particular way, a so called "giant"or "colossal" permittivity value (larger than 300 000) with unusual temperature dependence. In this paper, we report the very last results obtained on these two different types of materials.