Electromechanical anisotropy behavior in Pb_0.88Eu_0.08Ti_1−yMn_yO₃ system: Role of 90° domain reversal

Abstract

An indirect observation of 90°domain reversal under the influence of a poling field process was undertaken by an x-ray diffraction study in the Pb 0.88 Eu 0.08 Ti 1−y Mn y O 3 (y ‫ס‬ 0, 0.01, 0.02, and 0.03) piezoelectric anisotropic system. The optimum condition k p → 0 was achieved for y ‫ס‬ 0.02 composition. A large percentage of 90°domain rotation was necessary, but not a sufficient condition for the ultrahigh electromechanical anisotropy manifestation. A large microstrain originated by structural defects in unpoled samples seemed to play a crucial role in the attainment of this piezoelectric anisotropy. A breaking in the translational periodicity due to induced vacancy in Pb and O sites by Eu 3+ and Mn 2+ substitutions was manifested in the nonuniform variance of the tetragonality (c/a), the large microstrain, and the detriment of crystallinity observed.

Dielectric relaxation and conductivity behavior in modified lead titanate ferroelectric ceramics

“…The ionic radius of the Mn 2+ ion is similar to that of the Ti 4+ ion (0.81 and 0.74 Å, respectively, considering the corresponding coordination number for the B site of the perovskite structure) [20] and thereby upon manganese substitution an important effect on the structural parameters is not expected. Note that we have considered Mn 2+ because previous studies have shown that a Mn 4+ /Mn 2+ reduction takes place during the sintering process for this type of materials [10,18,19].…”

“…It is well known that PbTiO 3 (PT) undergoes a single ferroelectric transition from cubic to tetragonal [1] at around 490 • C, whereby the polar tetragonal state is stabilized by the large tetragonal strain in the c axis brought about by Pb-O hybridization. Systematic studies of the crystal structures, microstructures and electrical properties on modified PT have been developed in the last decades [1][2][3][4][5][6][7][8][9][10][11][12]. The sintering of pure PT ceramics is very difficult because of the large tetragonality, which it has been shown can be reduced greatly by the partial substitution of the Pb 2+ or Ti 4+ ions [1][2][3][4][5][6][9][10][11][12].…”

“…Systematic studies of the crystal structures, microstructures and electrical properties on modified PT have been developed in the last decades [1][2][3][4][5][6][7][8][9][10][11][12]. The sintering of pure PT ceramics is very difficult because of the large tetragonality, which it has been shown can be reduced greatly by the partial substitution of the Pb 2+ or Ti 4+ ions [1][2][3][4][5][6][9][10][11][12]. It is known that dense ceramics could be obtained by the partial substitution of rare earth elements in modified lead titanate [9,10,[13][14][15][16], which conserves the electromechanical anisotropy in the piezoelectric effect.…”

“…The sintering of pure PT ceramics is very difficult because of the large tetragonality, which it has been shown can be reduced greatly by the partial substitution of the Pb 2+ or Ti 4+ ions [1][2][3][4][5][6][9][10][11][12]. It is known that dense ceramics could be obtained by the partial substitution of rare earth elements in modified lead titanate [9,10,[13][14][15][16], which conserves the electromechanical anisotropy in the piezoelectric effect. The inherent anisotropy in the piezoelectric effect depends on the 3 Author to whom any correspondence should be addressed.…”

“…It has been shown that modification by using manganese, which occupies B sites, provides new structural defects, i.e. oxygen vacancies, produced by Mn 4+ /Mn 2+ reduction, during the sintering process [10,18,19].…”