| Materials Science & Chemical Engineering |
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| Study of the behaviour of the dielectric constant in Cu,Fe:BaTiO3 |
| Alioune OUEDRAOGO, Kalifa PALM, Issaka OUEDRAOGO, Guy CHANUSSOT |
| Laboratory of Applied Organic Chemistry and Physics, UFR/SEA, University of Ouagadougou, BP 7021 Ouagadougou, Burkina Faso; Laboratory of Dielectrics, University of Dijon, 21000 Dijon, France |
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Abstract In this work we study the behaviour of the dielectric constant of BaTiO3 single crystals doped with Cu and Fe for different ion percentages, particularly, the influence of these heterovalent substitutions on the ferroelectric-paraelectric phase transition whose temperature is found at Tc=120 °C for pure samples. The dielectric constant ε in terms of temperature shows that the Curie temperature decreases when the quantity of impurities increases and presents a broadening and flattering of the maximum of ε(T) within higher values, with the transition becoming more and more diffuse. It is interesting to have a material with very high permittivity (high-k) because of its capacity to store an important quantity of electric charges. The ε anisotropy and the Curie-Weiss law are also verified with a good ratio between the slopes of ε−1(T) from both sides of the transition, leading to a Curie constant: C=13×104 K for BaTiO3:1.6%Fe in the polar phase. BaTiO3 is a displacive ferroelectric going through a first-order phase transition. The substitutions have an effect on the dynamics of the perovskite lattice. They induce charges transfer to Ti and a diminution of elastic forces in BaTiO3. Then we discuss the fact that the maximum of permittivity does not depend on the phase transition but on the nature of the material.
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Received: 29 September 2007
Published: 18 January 2008
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