Piezoelectric properties of nonstoichiometric Sr1-xBi2+2x/3Ta2O9 ceramics -: art. no. 124101

The effect of poling on the structural, dielectric, and piezoelectric properties has been investigated for sol-gel-derived strontium bismuth tantalate (SBT) [Sr1-xBi2+2x/3Ta2O9] ceramics with x=0.0,0.15,0.30,0.45. The dielectric and ferroelectric properties are found to improve with increase in x up to 0.3. Beyond x > 0.3 the properties are found to degrade due to the limited solid solubility and the presence of a mixed phase of bismuth tantalate (BiTaO4) is detected with x=0.45. Poling treatment reduces the dielectric dispersion and dielectric loss in the frequency range (0.1-100 kHz). The resonance and antiresonance frequencies increase with increase in x (x=0-0.30), and the corresponding minimum impedance decreases. The measured coupling coefficients (k(p)) are small (0.0967-0.1) for x=0-0.30, and the electromechanical quality factor (Q(m)=915) is a maximum for the Sr0.7Bi2.2Ta2O9 composition (x=0.30). The estimated piezoelectric charge coefficient (d(31)) and piezoelectric voltage coefficient (g(31)) are 5.2 pC/N and 5.8x10(-3) V m/N, respectively. The positive values of d(31) and g(31) and the low dielectric permittivity of SBT yield a high value for the hydrostatic coefficients, despite the low charge coefficient of d(33)=24 pC/N. The maximum values of charge coefficient (d(h)=34 pC/N) and voltage coefficient (g(h)=39x10(-3) V m/N) are obtained for Sr0.7Bi2.2Ta2O9 composition, and the estimated hydrostatic figure of merit (d(h)g(h)x10(-15)=1215 m(2)/N) is high. (c) 2005 American Institute of Physics.