Polarized Raman and electrical study of single crystalline titanium modified lead magnesio-niobate

Abstract

Raman scattering experiments were performed on the relaxor ferroelectric lead magnesio-niobate (PMN), the ferroelectric 0.8 PMN-0.2 (PT) and the intermediate composition 0.9 PMN-0.1 PT. In order to understand in more detail the behaviour of this series, Raman scattering spectra were also collected under dc electric field. A ferroelectric phase could be induced in the latter composition for electric fields higher than a threshold value. The behaviour of this field-induced phase was compared with the (zero-field) ferroelectric phase in 0.8 PMN-0.2 PT. Barkhausen jumps were observed in the pyroelectric current measurements, and a strong dielectric anomaly was detected in zero field heating after field cooling experiments on 0.9 PMN-0.1 PT. These results are consistent with a description of the behaviour in this series based on a cancellation of 1:1 (Mg:Nb) domain random fields by titanium ions, favouring the onset of long range ferroelectric order.

Raman Scattering of 0.91Pb(Zn1/3Nb2/3)O3–0.09PbTiO3Relaxor Ferroelectric Single Crystals

“…The degree of order was increased only under an external electric field, thus, the transition could be observed by Raman spectra. 22) The large degree of order could be confirmed by detailed analysis of Raman spectra for pure PZN, although the authors did not reach this conclusion. If they had plotted a graph similar to Fig.…”

“…7,14,15) Since the vibrational spectrum has a shorter characteristic length scale than that required for diffraction experiments, the Raman spectrum is a good microprobe for the proposed nanodomain structures that are important for the interpretation of the properties of relaxors. Raman scattering study of the PMN system has been conducted by many authors: [16][17][18][19][20][21][22] the spectra are typical for relaxors, no soft modes are observed, and all the bands are broad in comparison with those of normal ferroelectrics. Idink and White found abrupt changes in the frequency and damping factor of certain bending modes by carefully fitting the spectra, but the microscopic origin remained unclear.…”

“…It is to be noted that the Raman spectra for 0.91PZN-0.09PT are somewhat different from those of PMN-PT system, where no phase transition was observed for compositions far from MPB. 22) The differences are probably due to the higher degree of order and the appearance of a tetragonal phase in 0.91PZN-0.09PT single crystal. This phenomenon seems to be perplexing at first glance, and the origins will be discussed later.…”

“…Marssi et al thought that the origin of Raman active modes is of the second order, but had no direct evidence to support this view. 22) In the case of 0.91PZN-0.09PT near the MPB, it undergoes rhombohedral to tetragonal and finally to cubic phase transition upon heating. This is different from the PMN system studied previously, [16][17][18][19][20][21] where the coexistence of tetragonal domains and spindle-like rhombohedral nanodomains was observed by optical microscopy, [5][6][7][8] therefore, a study of this crystal will be helpful to elucidate its relaxor behavior.…”

Bias-field effect on the temperature anomalies of dielectric permittivity inPbMg1∕3Nb2∕3

“…[1][2][3][4][5][6][7][8][9][10] Besides, they serve as model objects for studying relaxor properties. Relaxors represent a class of disordered crystals exhibiting a broad and frequency-dependent temperature maximum of the dielectric permittivity versus temperature instead of a sharp maximum inherent to normal ferroelectrics.…”