Polarization state in epitaxial thin films of relaxor ferroelectric PbMg1∕3Nb2∕3O3 (PMN) was experimentally studied at the nanoscale using a piezoresponse force microscopy (PFM). In the absence of a dc bias applied to the PFM tip, no piezoelectric activity could be found on most of the surface of the film. Under a moderate voltage (>1.5–2V), a polar state with a nonzero piezoresponse could be induced. Longer poling resulted in a significant reduction of the initial piezoresponse. After removing the bias field, a long-term relaxation of the piezoelectric signal obeying a Kohlrausch-Williams-Watt dependence was observed.

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Relaxor ferroelectric PbMg 1/3 Ta 2/3 O3 ceramics and thin films were investigated by means of broad-band dielectric, time-domain terahertz (THz) and Fourier-transform infrared (IR) spectroscopy in the frequency range 100 Hz -90 THz at temperatures 100 -490 K, the THz and IR spectra were studied from 20 to 900 K. Diffused and strongly temperature dependent peak in the complex permittivity is caused by a dielectric relaxation due to the dynamics of polar clusters. The relaxation appears below Burns temperature T d in the THz range, slows down on cooling through the microwave and MHz range and anomalously broadens. The shortest and longest relaxation times of the distribution of relaxation times follow Arrhenius and Vogel-Fulcher law, respectively. The degree of B-site order has only a small influence on the parameters of the dielectric relaxation and almost no influence on the phonon parameters. Below Tm ∼ =180 K the distribution of relaxation frequencies becomes broader than our experimental spectral range and frequency independent dielectric losses develop below 100 GHz in the spectra. Although the macroscopic crystal structure is cubic, IR spectra give evidence about the lower local symmetry which can be assigned to the presence of polar clusters below T d . Infrared spectra above T d still reveal more modes than predicted by selection rules in the paraelectric phase of the F m3m space group so that we suggest selection rules which take into account chemical inhomogeneity in the β"-perovskite sublattice.

Significant enhancement of energy-storage performance of (Pb0.91La0.09)(Zr0.65Ti0.35)O3 relaxor ferroelectric thin films by Mn doping Large enhancement of energy-storage properties of compositional graded (Pb1−xLax)(Zr0.65Ti0.35)O3 relaxor ferroelectric thick films Appl. Phys. Lett. 103, 113902 (2013); 10.1063/1.4821209 Field-induced dielectric properties of laser ablated antiferroelectric ( Pb 0.99 Nb 0.02 )(Zr 0.57 Sn 0.38 Ti 0.05 ) 0.98 O 3 thin films

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Several SrTiO 3 (STO) thin films without electrodes processed by pulsed laser deposition, of thicknesses down to 40 nm, were studied using infrared transmission and reflection spectroscopy. The complex dielectric responses of polar phonon modes, particularly ferroelectric soft mode, in the films were determined quantitatively. The compressed epitaxial STO films on (100) La 0.18 Sr 0.82 Al 0.59-Ta 0.41 O 3 substrates (strain 0.9%) show strongly stiffened phonon responses, whereas the soft mode in polycrystalline film on (0001) sapphire substrate shows a strong broadening due to grain boundaries and/or other inhomogeneities and defects. The stiffened soft mode is responsible for a much lower static permittivity in the plane of the compressed film than in the bulk samples.Keywords Soft mode . Thin film . Infrared spectroscopy SrTiO 3 (STO) is a classical incipient ferroelectric with strongly increasing permittivity on cooling-up to more than 20,000 in single crystals [1]. It is well known since 1994 [1] that the permittivity in STO thin films is strongly reduced and does not increase on cooling as much as in single crystals. It is thickness dependent, but even in the limit of very thick films it does not reach the crystal values [2]. The thickness dependence was assigned to lowpermittivity (dead) interfacial layers between the film and electrodes [2]. However, grain boundaries also play an important role in bulk ceramics as well as in thin films [3][4][5][6]. Low-permittivity grain boundaries and possible nanocracks in the films and/or ceramics decrease the effective permittivity, which is accompanied by a remarkable stiffening of the effective soft mode.Strain induced by the substrate may also influence the dielectric response of epitaxial films. The phase diagram of STO under uniaxial (biaxial) pressure was theoretically calculated from the known thermodynamic parameters [7,8]; it appears to be very sensitive to both compressive and tensile stresses. The ferroelectric transition may be also induced by the choice of appropriate substrate. For instance, the tensile in-plane stress produced by a (110) DyScO 3 substrate may induce the in-plane ferroelectricity up to room temperature [9]. Quasi-epitaxial film on (0001) sapphire exhibited ferroelectric transition near 120 K as evidenced by a softer TO 1 mode above 120 K compared to the single crystals [5]. Below the structural transition occurring probably at the same temperature, the TO 1 mode couples with the structural soft mode doublet and hardens on further cooling. On the other hand, the compressive stress induced by a (110) NdGaO 3 (NGO) substrate is responsible for the out-of plane ferroelectricity near 150 K [10] whereas the in-plane mode softening with decreasing temperature is only very weak. In the latter case, the in-J Electroceram (

The dynamic dielectric response of epitaxial PbMg 1/3 Nb 2/3 O 3 thin films was experimentally studied as a function of amplitude of ac electric field including very large amplitudes ͑to 10 MV/ m͒. For all amplitudes, a typical glasslike relaxor behavior was evidenced by the Vogel-Fulcher relationship, empirical scaling of the dielectric peak, and a broadening of the relaxation time spectra on cooling. With increasing amplitude of the ac field, both the temperature of the dielectric maxima and the freezing temperature decreased, the relaxation time spectrum became narrower, and the nonlinear permittivity was nonmonotonic. The comparison of the observed dielectric behavior with that under an applied small dc electric field and with the results of modeling revealed an orientational contribution to polarization.