Lead free BNKFT ceramics were synthesized by the
combustion technique. The variations of x and y contents
directly affect the crystal structure, microstructure, density
dielectric, ferroelectric and piezoelectric properties of the
BNKFT-x/0.03 and BNKFT-0.18/y ceramics. The XRD
indicated that the ceramics possess pure single phase of
perovskite structure, indicating that Kþ and Feþ have
diffused into the lattice. With increasing x and y contents,
grain size decreases and increases, respectively. The optimum
electric properties can be obtained at x¼0.18 and
y¼0.03, as follows: r¼5.85 g/cm3, er¼7850, tan d¼0.02,
Pr¼20.1 mC/cm2 (measured at 40 kV/cm) and d33¼213
pC/N. With superior electric properties, this work indicates
that the BNKFT-x/y ceramics prepared by the
combustion technique are better than the BNKFT-x/y
ceramics prepared by solid state.