Effect of Molecular Mass of B-site Ions on Electromechanical Coupling Factors of Lead-Based Perovskite Piezoelectric Materials

Abstract

The effects of the molecular mass of B-site ions of Pb(B′B′′)O3–PbTiO3 (B′=Mg, Zn, Ni, Sc, In and Yb; B′′=Nb and Ta) and Pb(B, Ti)O3 (B=Zr, Hf and Sn) piezoelectric materials on the electromechanical coupling factors were investigated. The relationship between the electromechanical coupling factor kp near a morphotropic phase boundary (MPB) and the molecular mass of B-site ions is systematically discussed. The reason why kp of Pb(Zr, Ti)O3 (PZT) is larger than that of Pb(Hf, Ti)O3 (PHT) or Pb(Sn, Ti)O3 (PST) is explained in terms of the molecular mass difference between A-site and B-site ions of Pb(B, Ti)O3. It may be concluded that a combination of the B-site ions which have a lower molecular mass in MPB composition, play an important role in realizing large electromechanical coupling factors in lead-based perovskites. From this viewpoint, MPB compositions of Pb[(Sc1/2Nb1/2)0.58Ti0.42]O3 (PSNT 58/42), which has the largest molecular mass difference between A-site and B-site (Amass-Bmass=147.1) ions may be the best combinations of all Pb(B′B′′)O3–PbTiO3 and Pb(B, Ti)O3 systems so far reported. However, if Pb[(Al1/2Nb1/2)1-xTix]O3 and Pb[(Ga1/2Nb1/2)1-xTix]O3 systems can be synthesized into pure perovskite structures near the MPB, a better piezoelectric performance than PZT 53/47 or PSNT 58/42 is expected.