Effect of Nb Doping on the Dielectric and Strain Properties of Lead-free 0.94(Bi1/2Na1/2)TiO3-0.06BaTiO3 Ceramics

(Bi1/2Na1/2)(0.94)Ba-0.06(Ti1-xNbx)O-3 (BNBTxNb) ceramics were investigated in terms of the crystal structure as well as the ferroelectric, dielectric, and piezoelectric properties. While little change was observed in the microstructure except for a slight decrease in the average grain size, a significant change was noticed in the temperature dependence of dielectric and piezoelectric properties. It was shown that the property changes are closely related to the downward shift in the position of the ferroelectric-to-relaxor transition temperature with increasing amount of Nb doping. A special emphasis is put on the fact that Nb doping is so effective at decreasing the ferroelectric-to-relaxor transition temperature that even at no more than 2 at.% Nb addition, the transition temperature was already brought down slightly below room temperature, resulting in the birth of a large strain at 0.46 %, equivalent to S-max/E-max = 767 pm/V.