Structure and dielectric properties of the (1-x)La(Mg1/2Ti1/2)O3-x(Na1/2Bi1/2)TiO3 microwave ceramics

The (1-x)La(Mg1/2Ti1/2)O3-x(Na1/2Bi1/2)TiO3 perovskite ceramics (0≤x≤0.6) were characterized with respect to both crystal structure and dielectric properties. The crystal structure of the solid solutions was investigated by x-ray diffraction (XRD) and the sequence of composition-driven structure transformations was revealed: P 21/n (0≤x≤0.2), a coexistence of Pnma and R3-barc (at the vicinity of x 0.3), and R3-barc (0.4≤x≤0.6). The dielectric response of the ceramics was measured as a function of temperature and composition. The range between x = 0.3 and 0.4, where the temperature coefficient of the resonant frequency passes the zero value, is associated with a discontinuous phase transition between orthorhombic and rhombohedral structure modifications. The compositional variation of the fundamental dielectric parameters, estimated at different frequency ranges, is discussed in relation to the crystal chemistry of the system