A new relaxor ferroelectric system of (1-x)BaTiO3-xBiAlO3 solid solution

In our continued effort of searching for lead-free ferroelectric materials, a new lead-free ferroelectric solid solution of (1-x)BaTiO3-xBiAlO3 (x = 0.02, 0.05, 0.10, and 0.15) has been synthesized by solid state reactions. XRD patterns show a transformation of the tetragonal symmetry into a rhombohedral symmetry as a result of the substitutions of Bi³⁺ on the A site and Al³⁺ on the B site in the lattice of BaTiO3. The temperature and frequency dependences of the dielectric constant indicate a crossover from a normal ferroelectric to relaxor behavior as x increases. Typical relaxor behavior is observed for x=0.15 with the temperature of the dielectric peak Tm = 360 K at 1 kHz, while ferroelectric hysteresis loop is displayed at room temperature, suggesting that the long-range polar order from the end member BaTiO3 persists and coexists with polar nanoregions induced by the chemical disorder due to the substitutions in the solid solution. With the sintering temperature decreased from 1350 °C to 1250 °C, the relaxor behaviour is enhanced while Tm decreases.