title: Effects of Al substitution on the spontaneous polarization and lattice dynamics of the PbTi1-xAlxO3.
abstract: Al-doped PbTiO3 solid solutions were synthesized by a solid state method. Since Al does not have bonding d-orbit or d-electrons, and the substitutions of Al(3+) for Ti(4+) in PbTiO3 is aliovalent, the effect of Al on the structure and spontaneous polarization is quite different from that of Hf, Zr, etc. substitutions in PbTiO3. Usually, the spontaneous polarization is weakened with decreased tetragonality in PbZrxTi1-xO3 and PbHfxTi1-xO3 systems; PbTi1-xAlxO3 (0 ≤ x ≤ 0.10) solid solutions exhibit improved spontaneous polarization with decreased tetragonality (c/a). Lattice dynamics and the crystal structure of PbTi1-xAlxO3 with enhanced spontaneous polarization were investigated by FT-IR, Raman scattering technique, and X-Ray Rietveld method. The Al-doping reinforced the covalence of Pb-O(II), which indicated that the Pb-O hybridization was strengthened. The three transverse optical (TO) modes of A1-symmetry in Raman and the "stretching" and "bending" vibration modes in FTIR further verified the increase of spontaneous polarization (PS) in the A- and B-sites.
authors.affiliation: Department of Physical Chemistry, University of Science and Technology Beijing, Beijing, 100083, P. R. China. xing@ustb.edu.cn.
authors.forename: Ce
authors.initials: C
authors.lastname: Sun
authors.forename: Jinquo
authors.initials: J
authors.lastname: Wang
authors.forename: Penghao
authors.initials: P
authors.lastname: Hu
authors.forename: Moon J
authors.initials: MJ
authors.lastname: Kim
authors.forename: Xianran
authors.initials: X
authors.lastname: Xing