Piezoelectric properties of SrBi2M2− xVxO9 (M = Nb and Ta) ceramics

Vanadium-substituted strontium bismuth tantalate, Sr_0.8Bi_2.2Ta_{2− x}V_xO₉ (SBTVx), and strontium bismuth niobate, SrBi₂Nb_{2− x}V_xO₉ (SBNVx), ceramics were synthesized by a low-temperature processing, and their dielectric, ferroelectric and piezoelectric properties were characterized. With the partial substitution of tantalum or niobium by vanadium cations, the single phase of the ABi₂M₂O₉-type structure was preserved and the sintering temperature was significantly decreased. For the SBNV ceramics, the T _c of 437^∘C for x = 0.0, the vanadium content hardly changed. On the other hand, the T _c of the SBTV ceramics increased from 408^∘C for the non-substituted SBTV to 414^∘C for x = 0.05 and then with the increasing vanadium content, the T _c decreased to 379^∘C for x = 0.20. The remanent polarizations, P _r, of SBTV and SBNV at room temperature were 4.9 and 5.4 μC/cm², respectively. All the obtained independent electromechanical coupling factors of the SBTV0.05 ceramics were as follows: k _p = 0.119, k ₃₁ = 0.073, k ₃₃ = 0.165, k ₁₅ = 0.051 and k _t = 0.134, and the SBNV0.05 ceramics were as follows: k _p = 0.074, k ₃₁ = 0.045, k ₃₃ = 0.175, k ₁₅ = 0.106 and k _t = 0.140. These coupling factors were higher than those of the non-substituted materials. From these results, the vanadium-substituted SBT and SBN-based materials can be expected to be lead-free piezoelectric resonator materials that can be prepared at low sintering temperatures.