Bismuth zinc niobate: BZN-BT, a new lead-free BaTiO3-based ferroelectric relaxor?

The novel lead-free ferroelectric relaxor system x(Bi(Zn2/3Nb1/3)O-3)(1-x)BaTiO3 (xBZN(1-x)BT) has received interest as a high-capacity relaxor dielectric material. Small quantities (< 10.0 mol.%) of BZN-based dopant had significant impacts on the structure of the BaTiO3 host. This study evaluates the effect of BZN additions to the BaTiO3 host up to xBZN = 10.0%. Initial additions of BZN were observed to stabilize tetragonal and orthorhombic coexistence at 295 K, alongside increasing dielectric constant. Peak dielectric constant and polarization were observed at x < 4.0%, coinciding with maximum orthorhombic intensity and a local minima in tetragonal intensity. Compositions 0 < x < 4.0% showed increasing polarization and a drop in T-m and classical ferroelectric properties. No significant dielectric dispersion was observed for compositions x < 4.0% over the frequency range 5-640 kHz. Compositions at x > 4.0% showed the onset of dielectric relaxation alongside a drop in polarization coincident with a drop in the tetragonal c(T)/a(T) ratio and the onset of the cubic phase at 295 K. Peak piezoelectric, dielectric and polarization values occurred over the range 3.8% < x < 4.0%, alongside maximum orthorhombic intensity. Subsequent BZN additions showed a rapid onset of dielectric relaxation, alongside an increase in cubic intensity and a continuous drop in T-m with a minima near x = 7.0%. Tetragonal presence at 295 K also vanished to zero at x = 7.0%. Polarization loops ceased showing ferroelectric characteristics at x > 5.0%, showing a transition from lossy relaxor dielectric to low-loss relaxor dielectric at x > 10.0%.