Ferroelectric ceramics in the Na/sub 0.5/Bi/sub 0.5/TiO/sub 3/-K/sub 0.5/Bi/sub 0.5/TiO/sub 3/, Na/sub 0.5/Bi/sub 0.5/TiO/sub 3/-PbTiO/sub 3/ and K/sub 0.5/Bi/sub 0.5/TiO/sub 3/-PbTiO/sub 3/ systems

The study of the Na/sub 0.5/Bi/sub 0.5/TiO/sub 3/-K/sub 0.5/Bi/sub 0.5/TiO/sub 3/, Na/sub 0.5/Bi/sub 0.5/TiO/sub 3/-PbTiO/sub 3/ and K/sub 0.5/Bi/sub 0.5/TiO/sub 3/-PbTiO/sub 3/ systems was carried our using X-ray diffraction, DSC and dielectric measurements. The limits of the rhombohedral (Na/sub 0.5/Bi/sub 0.5/TiO/sub 3/-rich side) and orthorhombic (K/sub 0.5/Bi/sub 0.5/TiO/sub 3/, and PbTiO/sub 3/-rich side) solid solutions were determined, as well as the evolutions of their lattice parameters as a function of composition. Ceramic materials have been prepared by natural sintering (1090-1220/spl deg/C/0.5 h) of powders obtained by solid state reaction (900-1000/spl deg/C/20 h) of the corresponding oxides and carbonates. The dielectric permittivities of these materials have been measured in a wide frequency range between 20 and 800/spl deg/C. The results showed that they all are ferroelectric at room temperature and some of them exhibit a relaxer-type behaviour. Several specular compositions showed the best piezoelectric characteristics for this type of ceramic materials.