Effects of B-site Ions on the Electromechanical Coupling Factors of Pb(B′B′′)O3–PbTiO3 Piezoelectric Materials

The effect of B-site ions of Pb(B′B′′)O3–PbTiO3 (B′=Zn, Mg, Ni, Ga, Sc, In, Yb and B′′=Nb, Ta) piezoelectric materials on the electromechanical coupling factors has been studied. A relationship between electromechanical coupling factor k p near a morphotropic phase boundary (MPB) and an order/disorder tendency of B-site ions is systematically discussed. The reason why k p of Pb[((Sc1/2Nb1/2)0.58Ti0.42)O3 (PSNT59/42) is larger than that of Pb[(Mg1/3Nb2/3)0.68Ti0.32]O3 (PMNT68/32) or Pb[((Sc1/2Ta1/2)0.58Ti0.42)O3 (PSTT55/45) was explained in terms of the disorder tendency of B-site ions of Pb(B′B′′)O3–PbTiO3. It may be concluded that a combination of the B-site elements which have a tendency of disorder play an important role in bringing about large electromechnical coupling factors in MPB composition. From this viewpoint, MPB compositions of Pb[((Sc1/2Nb1/2)0.29(Mg1/3Nb2/3)0.34Ti0.37]O3 (PSMNT 29/34/37) and Pb[((Sc1/2Nb1/2)0.36(Ni1/3Nb2/3)0.26Ti0.38]O3 (PSNNT 36/26/38) maybe the two best combinations among all the Pb((B′B′′)O3–PbTiO3 systems.