Ferroelectric Properties of Monoclinic Pb(Mg1/3Nb2/3)O3 - PbTiO3 Crystals

TL;DR

This study investigates the ferroelectric, dielectric, and piezoelectric properties of the recently discovered monoclinic Pm phase in Pb(Mg1/3Nb2/3)O3 - PbTiO3 crystals, revealing its distinct behavior near the morphotropic phase boundary.

Contribution

It provides the first detailed characterization of the monoclinic Pm phase's ferroelectric and piezoelectric properties in this system, highlighting differences from the rhombohedral phase.

Findings

Monoclinic Pm phase shows ferroelectric hysteresis with 23 μC/cm^2 polarization.

Piezoelectric response (d33) is weaker than in the rhombohedral phase.

Dielectric permittivity (~2500) is smaller, but electromechanical coupling (kt=0.60) is similar.

Abstract

A monoclinic phase was recently discovered near the morphotropic phase boundary in several high-performance piezoelectric perovskite solid solutions, but its properties have not been reported. In this paper the dielectric, piezo- and ferroelectric properties of the monoclinic Pm phase in the (1-x)Pb(Mg1/3Nb2/3)O3 -xPbTiO3 perovskite system are studied. In a (001)-oriented crystal of composition x=0.33, ferroelectric hysteresis loops with remanent polarization of 23 uC/cm^2 are displayed. In poled monoclinic crystals, under unipolar drive up to 10 kV/cm, the domain walls remain unchanged, the polarization and longitudinal strain change almost linearly, but the piezoelectric response (d33=9x10^(-10) C/N) is much weaker than in the rhombohedral phase of close composition. The relative dielectric permittivity of the Pm phase is also smaller (with a small-signal value of ~ 2500), but the piezoelectric constant (g33 = 3 x10^(-2) m^2/C) and the electromechanical coupling factor (kt = 0.60) are practically the same as in the rhombohedral phase. The properties of the various phases in the range of the morphotropic phase boundary are related to the different rotation paths of the polarization vector induced by the external drive.