Mn Effect on Nonlinear and Structural Properties of &amp;lt;110&amp;gt; Oriented PZN-4.5PT Single Crystals

Diouma Kobor,Modou Tine,Daniel Guyomar,Abdelowahed Hajjaji,Laurent Lebrun

doi:10.4236/jmp.2012.35056

Abstract

Ferroelectric single crystals Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) are promising full materials for non resonant or large bandwidth transducers due to the large values of their piezoelectric properties (d ij , k ij ) and their low mechanical quality factor (Q ij ). Many studies on oriented PZN-4.5PT single crystals were carried out but it is very difficult to find research findings on oriented Mn doped PZN-PT. Thus, investigations were made using XRD, Raman and EPR characterization for oriented PZN-4.5PT grown through the Flux method. Mn doping effect on structural, dielectric, mechanical and piezoelectric properties with two values of Mn percentage (1 and 2 mol%) are also reported in this paper. Through the XRD study, the lattice parameters of doped PZN-PT crystals are slightly increased compared to the undoped one but the Mn didn’t change its structure. The room temperature dielectric permittivity along direction is about 1572 and 1626 (respectively 1% and 2% Mn doped crystals) which are much lower than that of the undoped PZN-4.5PT (2553). The remnant polarization and coercive field of oriented doped crystal measured at 1 KHz are respectively 30 μC/cm2 and 4.30 kV/cm (PZN-4.5PT), 32 μC/cm2 and 6.10 kV/cm (PZN-4.5PT + 1% Mn) and 28 μC/cm2 and 7.30 kV/cm (for the 2% Mn doped crystal). The mechanical quality factor Qm changed from 139 to 441 respectively for the pure and 1% Mn doped single crystals at room temperature while it decreases slightly to 336 for the 2 mol% Mn doped.

Highlights

The performance of transducers can be significantly increased by the use of active materials with large piezoelectric coefficients and large coupling factors [1]
From the peak profiles of the pseudo-cubic (200) and (222) reflections, the symmetry is clearly seen to be rhombohedral [9]. These results show that the Mn doping didn’t change the single crystals structure at room temperature
They create a large temperature interval for the crystal’s application by increasing the Tc and Ec values. This behavior confirms the role of Mn which is the crystal’s stabilization. These results show that Mn is acting as a hardener, by decreasing the piezoelectric and dielectric properties and increasing the mechanical properties in the PZN-PT crystals

Summary

Introduction

The performance of transducers can be significantly increased by the use of active materials with large piezoelectric coefficients (dij) and large coupling factors (kij) [1]. High levels of piezoelectricity have been published in Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) and Pb(Zn1/3Nb2/3)O3PbTiO3 (PZN-PT) single crystals: d33 > 2500 pC/N, d31> –1500 pC/N, k33 > 90%, k31 > 80% and kt > 60% [1,2,3,4,5]. Though these crystals have excellent piezoelectric constants and electromechanical coupling factors, they have very low mechanical quality factor values (Qm < 100) which in turn reduces their potential for high power applications or resonant based transducers [1,2,4]. Analagous to acceptor doping in polycrystalline PZT ceramics PZN-4.5PT single crystals were doped with Manganese

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