Composition dependence of the multifunctional properties of Nd-doped Bi4Ti3O12 ceramics

Sample preparation, evolution of the crystal structure with Nd content at room temperature, as well as dielectric and magnetic properties of polycrystalline Bi4-xNdxTi3O12 solid solutions (x = 0.0, 0.5, 1.0, 1.5, and 2.0) are reported. These solid solutions were structurally characterized by X-ray powder diffraction using Rietveld refinements. For x <= 1.0, the samples crystallize in an orthorhombic symmetry. The structural data could be refined using the polar orthorhombic space group B2cb. The orthorhombicity decreases with increasing Nd3+ concentration, and a paraelectric tetragonal structure (space group I4/mmm) is stabilized for x > 1. The ferroelectric Curie temperature was found to monotonously decrease with increasing Nd concentration. A polar-to-nonpolar phase transition takes place near x = 1, reflecting the existence of a morphotropic phase boundary between 1.0 < x < 1.5 at room temperature. All samples were found to be paramagnetic down to 5 K, however, the presence of significant antiferromagnetic interaction is inferred from Curie-Weiss analyses of the temperature dependence of the magnetic susceptibility of the doped samples. The effect of Nd3+ substitution on structure-property relationship is discussed and compared to that of other lanthanide cations.