Alkaline niobate based lead-free piezoelectric ceramics have been widely investigated in last few yeas since they could exhibit excellent dielectric,ferroelectric and piezoelectric properties near a polymorphic phase boundary(PPB)which was formed by either simply shifting the high-temperature orthorhombic-tetragonal(O-T)polymorphic phase transition temperature down to room temperature or raising low-temperature rhombohedralorthorhombic(R-O)phase transition temperature to room temperature,or changing the temperature range for the R and T phase zone.