Freezing of the polarization fluctuations in lead magnesium niobate relaxors

Abstract

The dielectric relaxation of a solid solution of 10-mol % lead titanate in lead magnesium niobate is found to be similar to the magnetic relaxation in spin-glass systems.1–3 Based on this analogy, it is proposed that the relaxor ferroelectric is a polar-glassy system which has thermally activated polarization fluctuations above a static freezing temperature. An activation energy and freezing temperature of 0.0407 eV and 291.5 K, respectively, were found by analyzing the frequency dependence of the temperature of the dielectric maximum using the Vogel–Fulcher relationship.4,5 It has also been shown that a macroscopic polarization is sustained on heating up to this freezing temperature. A coupling between nanometer scale clusters is believed to control the kinetics of the fluctuations and the development of a frustration as the system freezes into states of local equilibrium. The possibility of an orientational freezing associated with the ferroelastic nature of the nanosized polar regions in the rhombohedral relaxor families as well as a polar freezing is discussed. A diffuse phase transformation is believed to arise due to a dispersion in the fluctuation frequency of the polarization. A qualitative model for the relaxation time spectrum is also proposed in which the width of the spectrum broadens strongly near the freezing temperature.

Development of nanoscale polarization fluctuations in relaxor-based (1-x)Pb(Zn1/3Nb2/Tsukada1, Hidaka2, Kojima3 et al. 2013Phys. Rev. B252250View full textAdd to dashboardCite

“…From the highest to the lowest, these are (i) the Burns temperature T B , 5 (ii) the intermediate temperature T * , [6][7][8] (iii) the frequency-dependent temperature of the dielectric permittivity peak T m , and (iv) the ferroelectric phase transition temperature T C [or the freezing temperature T f in the case in which this transition is absent as, e.g., in Pb(Mg 1/3 Nb 2/3 )O 3 (PMN)]. 9 Above T B , the phase is paraelectric without PNRs, and the structure is essentially the same as the paraelectric state of normal ferroelectrics. Below T B , in the so-called ergodic relaxor phase, the frustration between electric and spatial instabilities induces PNRs, despite the fact that the macroscopic crystal symmetry is identical to that above T B .…”

Anharmonic atomic vibrations in the relaxor ferroelectric Pb(Mg1/3Nb2/3)OYamanaka1, Ahart2, Nakamoto3 et al. 2012Phys. Rev. B8050View full textAdd to dashboardCite

“…Lead-based relaxor ferroelectrics with the perovskite structure exhibit a strong frequencydispersive dielectric permittivity with broad temperature dependence, superior piezoelectric response, and other peculiar properties [1][2][3]. In particular, the dielectric properties peak in a region of the phase diagram (pressure-temperature-composition) where the dielectric constant shows frequency dispersion and has a maximum with decreasing temperature.…”

“…In addition, their high permittivity and high piezoelectric constants make them suitable for applications in devices for sonar or medical imaging [1]. While extensive theoretical [3][4][5][6][7] and experimental studies [1][2][3][7][8][9][10][11][12] have advanced the fundamental understanding of relaxor behavior, their properties are still poorly understood. The difficulties stem from the complexity of these materials, which have a high degree of compositional, structural and polar disorder.…”

Manipulation of polar order in the “empty” tetragonal tungsten bronzes: Ba4-xSrxDy0.67□1.33Nb10O30, x = 0, 0.25, 0.5, 1, 2, 3

“…19,20 Higher occupancy of Sr on the A1-site leads to an increased t A1 tolerance factor for x = 2, such that t A1 (x = 2) > t A1 (x = 3) , Table 1. This multi-site occupancy by Sr generates two contributing factors which favour relaxor behaviour: 1) A-site disorder; and 2) reduced octahedral tilting due to the increase in A1-cation size (increased t A1 ).…”

“…where f is the frequency of the applied ac field, f 0 is the limiting response frequency, E a is the activation energy, k is Boltzmann's constant and T m is the maximum of the relative permittivity measured with ac field of frequency, f. [19][20][21] The polarisation freezes out at T f , the static freezing temperature, also known as the Vogel-Fulcher temperature. 19,20 Higher occupancy of Sr on the A1-site leads to an increased t A1 tolerance factor for x = 2, such that t A1 (x = 2) > t A1 (x = 3) , Table 1.…”