Structural and dielectric study of the Na_0.5Bi_0.5TiO₃–PbTiO₃ and K_0.5Bi_0.5TiO₃–PbTiO₃ systems

Abstract

A study of the Na_0.5Bi_0.5TiO₃ –PbTiO₃ and K_0.5Bi_0.5TiO₃-PbTiO₃ systems has been carried out using X-ray diffraction, differential scanning calorimetry and dielectric measurements. The limits of the rhombohedral (Na_0.5Bi_0.5TiO₃-rich side) and tetragonal (PbTiO₃-rich side) solid solutions have been determined, as well as the evolution of their lattice parameters as a function of composition and temperature. Ceramic materials have been prepared by natural sintering (1090–1220 °C; 0.5 h) of powders obtained by solid-state reaction (900–1000 °C; 20 h) of the corresponding oxides and carbonates. The dielectric permittivities of these materials have been measured in a wide frequency range for temperatures between 20 and 800 °C. The results showed that they all are ferroelectric at room temperature and exhibit either a diffuse, probably second-order phase transition, or a sharp, first-order-like phase transition from the ferroelectric to the paraelectric state, depending on the composition.

References

1. B. Jaffe, W. R. Cook and H. Jaffe, Piezoelectric Ceramics, Academic Press, London, 1971.
2. B. Vakhrushev, V. A. Isupov, B. E. Kvyatkovsky, N. M. Okuneva, I. P. Pronin, G. A. Smolenskii and P. P. Syrnikov, Ferroelectrics, 1985, 63, 153.
3. C. S. Tu, I. G. Siny and V. H. Schmidt, Phys. Rev. B, 1994, 49, 11550.
4. T. Takenaka, K. Sakata and K. Toda, Ferroelectrics, 1990, 106, 375.
5. K. Sakata and Y. Masuda, Ferroelectrics, 1974, 7, 347.
6. S.-E. Park and K. S. Hong, J. Appl. Phys, 1996, 79, 383.
7. G. A. Smolenskii, V. A. Isupov, A. I. Agranovskaia and N. N. Krainik, Fiz. Tvergodo Tela, 1960, 2, 2982.
8. O. Elkechai, M. Manier and J. P. Mercurio, Phys. Status Solidi A, in the press.
9. A. F. Devonshire, Philos. Mag., 1949, 40, 1040.