ELECTROMECHANICAL PROPERTIES OF LEAD-FREE PIEZOELECTRIC CERAMICS FOR (1-x)Na_(0.5)Bi_(0.5)TiO_(3)-xNaNbO_(3) SYSTEM

Lead-free piezoelectric ceramics of (1-x)Na_(0.5)Bi_(0.5)TiO_(3)-xNaNbO_(3)(x = 0—0.08 ) were fabricated by conventional ceramic preparation technique. X-ray diffraction patterns indicate that all ceramics studied can form pure perovskite structure. The dielectric constants as a function of temperature at different frequencies show that these ceramics are typical relaxor ferroelectric. The relaxor characteristic becomes more obvious with the increasing of the content of NaNbO_(3). Saturated polarization to electric field ((P-)E) hysteresis loops show that all ceramics are ferroelectrics at room temperature. When x=0.02, the remanent polarization P_(r) is at the maximum value for the ceramics, which corresponds to the maximum piezoelectric properties. It is found that the piezoelectric constant d_(33) and planar electromechanical coupling factor K_(p) increase first and then decrease with the increase of x value. The best d_(33) is 88 pC/N and K_(p )is 0.179 2. The dielectric constant e~T_(33)/e_0 and dielectric loss tan δ increase with increasing of x value.