Electric field-induced phase transitions were investigated in (111), (110), and (100) thin platelets of relaxor ferroelectric Pb(Mg 1∕3 Nb 2∕3 )O 3 single crystals with electric fields applied along the ⟨111⟩, ⟨110⟩, and ⟨100⟩ directions, respectively. Temperature dependences of complex dielectric permittivity, pyroelectric current and dielectric hysteresis loops were investigated. Electric field-temperature (E-T) phase diagrams were proposed for the different directions of the field. Alongside with the high-temperature ergodic relaxor phase and the low-temperature glassy nonergodic relaxor phase existing at E=0, the ferroelectric phase may appear in the diagram at the fields higher than the threshold field (E th ). The temperature of the first-order transition between ergodic relaxor and ferroelectric phases (T C ) was located in field cooling and field heating after fieldcooling regimes. For the ⟨111⟩ field direction, T C is higher and E th is lower than for the other directions. For the ⟨100⟩ direction, T C is the lowest and E th is the highest. The critical point bounding the T C (E) line when the field is applied in ⟨111⟩ direction [ Z. Kutnjak, J. Petzelt and R. Blinc Nature 441 956 (2006)] is not observed in the ⟨110⟩ and ⟨100⟩ directions up to the highest applied field of 7.5 kV∕cm. Extrapolation of experimental data suggests that the critical point for the ⟨110⟩ and ⟨100⟩ directions (if any) can be expected only at much higher fields. In the hysteresis loops experiments performed after zero-field cooling, the lower temperature limit is determined above which a ferroelectric phase can be induced from the frozen glassy state at a given field strength or the polarization of the induced ferroelectric phase can be reversed. This limit is located at much lower temperatures in the (100) platelet than in the (110) or (111) platelets. An additional ferroelectric rhombohedral to ferroelectric orthorhombic phase transition occurs in the (110) platelet at high electric fields (∼20 kV∕cm). The mechanisms of the field-induced transformation from the glassy nonergodic relaxor phase or the ergodic relaxor phase to the ferroelectric phase are discussed.Electric field-induced phase transitions were investigated in ͑111͒, ͑110͒, and ͑100͒ thin platelets of relaxor ferroelectric Pb͑Mg 1/3 Nb 2/3 ͒O 3 single crystals with electric fields applied along the ͗111͘, ͗110͘, and ͗100͘ directions, respectively. Temperature dependences of complex dielectric permittivity, pyroelectric current and dielectric hysteresis loops were investigated. Electric field-temperature ͑E-T͒ phase diagrams were proposed for the different directions of the field. Alongside with the high-temperature ergodic relaxor phase and the low-temperature glassy nonergodic relaxor phase existing at E = 0, the ferroelectric phase may appear in the diagram at the fields higher than the threshold field ͑E th ͒. The temperature of the first-order transition between ergodic relaxor and ferroelectric phases ͑T C ͒ was located in field cooling and field heating after fi...

We demonstrate uniform sign optical chirality generation in dimers of silicon (Si) nanodisks under linear light polarization through combination of experimental spectroscopy and electromagnetic simulations. Excitation of the magnetic dipole resonance in individual Si nanodisks generates enhanced electric and magnetic fields. We show that the fields provided by adjacent Si nanodisks excited with linearly polarized light at the magnetic dipole resonance can align to generate strong near-field chirality in the gap between the Si nanodisks. The near-field chirality enhancement for Si nanodisk dimers is compared with that for resonant gold (Au) nanoparticle dimers that provide almost exclusively electric field enhancement. We experimentally determine the third Stokes parameter, S 3 , of light transmitted through Si nanodisk dimers fabricated on sapphire as a measure for the chirality flux and the related near-field chirality. The experiments confirm the generation of uniform sign optical chirality in the Si nanodisk dimers whose handedness can be switched through choice of the orientation of the incident linear light polarization and whose amplitude decreases with increasing gap separation.

The 1:1 B-site cation order in Pb(Mg1/3Nb2/3)O3 relaxor ferroelectric ceramics was significantly enhanced by doping of minor amounts of La3+, Sc3+, or W6+ (less than 3 at. %) combined with a slow cooling procedure. Transmission electron microscopy examination confirmed the size increase of the cation-ordered regions embedded in a disordered matrix in the samples that were slowly cooled after sintering. The average cation ordering parameter (S) determined from x-ray diffraction data in these partially ordered samples was about 0.3-0.4. The ferroelectric properties and dielectric relaxation were compared in partially ordered and disordered (S=0) samples with the same composition. It was found that typical relaxor behavior was preserved in partially ordered ceramics. Furthermore, the temperature and diffuseness of the characteristic relaxor permittivity peak and the parameters of dielectric relaxation (in particular, the distribution of relaxation times and the Vogel-Fulcher freezing temperature) were practically independent of S. In contrast, the diffuseness of the phase transition from the ferroelectric phase (induced by external electric field) to the ergodic relaxor phase appeared to be much larger in the disordered samples than in the partially ordered ones (this diffuseness was assessed using pyroelectric current and ferroelectric hysteresis loops). These results suggest that cation ordering did not influence the behavior of polar nanoregions which are responsible for the dielectric response in the ergodic relaxor phase but significantly influenced the ferroelectric phase transition. The results are interpreted in terms of different types of polar regions in the disordered matrix and cationordered domains. The 1:1 B-site cation order in Pb͑Mg 1/3 Nb 2/3 ͒O 3 relaxor ferroelectric ceramics was significantly enhanced by doping of minor amounts of La 3+ , Sc 3+ , or W 6+ ͑less than 3 at. %͒ combined with a slow cooling procedure. Transmission electron microscopy examination confirmed the size increase of the cation-ordered regions embedded in a disordered matrix in the samples that were slowly cooled after sintering. The average cation ordering parameter ͑S͒ determined from x-ray diffraction data in these partially ordered samples was about 0.3-0.4. The ferroelectric properties and dielectric relaxation were compared in partially ordered and disordered ͑S =0͒ samples with the same composition. It was found that typical relaxor behavior was preserved in partially ordered ceramics. Furthermore, the temperature and diffuseness of the characteristic relaxor permittivity peak and the parameters of dielectric relaxation ͑in particular, the distribution of relaxation times and the Vogel-Fulcher freezing temperature͒ were practically independent of S. In contrast, the diffuseness of the phase transition from the ferroelectric phase ͑induced by external electric field͒ to the ergodic relaxor phase appeared to be much larger in the disordered samples than in the partially ordered ones ͑this diffuseness was assesse...

The effect of cation ordering on an electric field-induced relaxor to normal ferroelectric phase transition in Pb(Mg 1/3 Nb 2/3 )O 3 (PMN)-based ceramics was investigated. Both A-site La doping and B-site Sc doping were found to enhance the chemical ordering in these relaxor ceramics. However, the enhanced chemical orderings showed different impacts on the dielectric and ferroelectric properties in these perovskite materials. The 5% La doping was observed to shift the dielectric maximum temperature (T max ) to a significantly lower temperature and suppress the electric field-induced transition to a ferroelectric phase. In contrast, the 5% and 10% Sc doping showed little effect on T max but strengthened the ferroelectric coupling. The difference is discussed on the basis of cation size and charge imbalance. An electric field-temperature phase diagram is also proposed for the 0.90PMN-0.10Pb(Sc 1/2 Nb 1/2 )O 3 based on its history dependence of the electric field-induced phase transition. Disciplines Ceramic Materials | Electromagnetics and Photonics | Other Mechanical Engineering CommentsThis is the peer reviewed version of the following article: Journal of the American Ceramic Society 89, 202-209 (2006) The effect of cation ordering on the electric field-induced relaxor to normal ferroelectric phase transition in Pb(Mg1/3Nb2/3)O3-based ceramics was investigated. Both A-site, La-doping, and Bsite, Sc-doping, were found to enhance the chemical ordering in these relaxor ceramics. However, the enhanced chemical orderings showed different impacts on the dielectric and ferroelectric properties in these perovskite materials. The 5% La-doping was observed to shift the dielectric maximum temperature (Tmax) to a significantly lower temperature and suppress the electric fieldinduced transition to a ferroelectric phase. In contrast, the 5% and 10% Sc-doping showed little effect on Tmax but strengthened the ferroelectric coupling. The difference is discussed on the basis of cation size and charge imbalance. An electric field-temperature phase diagram is also proposed for the 0.90Pb(Mg1/3Nb2/3)O3-0.10Pb(Sc1/2Nb1/2)O3 based on its history dependence of the electric field-induced phase transition.

Optoplasmonic materials are metallo-dielectric hybrid structures that combine metallic and dielectric components in defined geometries in which plasmonic and photonic modes synergistically interact. These beneficial interactions can be harnessed by integrating plasmonic nanoantennas into defined photonic environments generated, for instance, by discrete optical resonators or extended systems of diffractively coupled nanoparticles. Optoplasmonic structures facilitate photonic-plasmonic mode coupling and offer degrees of freedom for creating optical fields with predefined amplitude and phase in space and time that are absent in conventional photonic or plasmonic structures. This Perspective reviews the fundamental electromagnetic mechanisms underlying selected optoplasmonic approaches with an emphasis on materials available through template-guided self-assembly strategies.

The complex structure of relaxor ferroelectrics comprises polar nanoregions (PNRs) which appear upon cooling below the Burns temperature and quenched compositional (chemical) disorder. The relation between the polar nanostructure and compositionally ordered regions (CORs) often observed in relaxors has been the subject of extensive theoretical investigations; however, the experimental data, especially concerning Pb(B′1/ 3B″2/3)O3-type complex perovskite relaxors, are rather limited. In this paper, we analyse and discuss the results of our recent investigations of the morphology of CORs and the dynamics of PNRs in Pb(Mg1/ 3Nb2/3)O3 based solid solutions in which the degree of compositional disorder was varied by means of changing the composition and/or by means of high-temperature annealing. The samples were characterised using X-ray diffraction, transmission electron microscopy, piezoresponse force microscopy, Brillouin light scattering, dielectric spectroscopy, as well as by measuring pyroelectric effect and ferroelectric hysteresis loops. No influence of the size of CORs on the PNRs relaxation in the ergodic relaxor phase is found. Instead, the CORs size influences significantly the diffuseness of the transition from the field-induced ferroelectric phase to the ergodic relaxor state. The results are interpreted in the framework of a model suggesting the coexistence of static and dynamic PNRs in the ergodic relaxor phase. Relaxor ferroelectrics / Compositional disorder / Lead magnesium niobate / Dielectric relaxation / Domain structure Abstract. The complex structure of relaxor ferroelectrics comprises polar nanoregions (PNRs) which appear upon cooling below the Burns temperature and quenched compositional (chemical) disorder. The relation between the polar nanostructure and compositionally ordered regions (CORs) often observed in relaxors has been the subject of extensive theoretical investigations; however, the experimental data, especially concerning Pb(B 0 1=3 B 00 2=3 )O 3 -type complex perovskite relaxors, are rather limited. In this paper, we analyse and discuss the results of our recent investigations of the morphology of CORs and the dynamics of PNRs in Pb(Mg 1/3 Nb 2/3 )O 3 -based solid solutions in which the degree of compositional disorder was varied by means of changing the composition and/or by means of high-temperature annealing. The samples were characterised using X-ray diffraction, transmission electron microscopy, piezoresponse force microscopy, Brillouin light scattering, dielectric spectroscopy, as well as by measuring pyroelectric effect and ferroelectric hysteresis loops. No influence of the size of CORs on the PNRs relaxation in the ergodic relaxor phase is found. Instead, the CORs size influences significantly the diffuseness of the transition from the field-induced ferroelectric phase to the ergodic relaxor state. The results are interpreted in the framework of a model suggesting the coexistence of static and dynamic PNRs in the ergodic relaxor phase.

Sc doping in Pb(Mg1/3Nb2/3)O3 enhances the B-site 1:1 cation order significantly but promotes the ferroelectric polar order moderately. At low doping levels, the electrical polar domains remain at the nanometer scale and the relaxor ferroelectric behavior is preserved. A normal ferroelectric state can be triggered with electric fields from the relaxor state at lower temperatures. This electric-field-induced phase transition process was directly observed with an in situtransmission electron microscopy technique in a 4at.% Sc-doped Pb(Mg1/3Nb2/3)O3 polycrystalline ceramic under different conditions. It was found that the phase transition started at the grain boundary and took two steps to complete: The gradual coalescence of the polar nanodomains and the abrupt formation of the long-range ferroelectric domains. During the growth of the polar nanodomains, the morphology of the cation ordered chemical domains does not change. Furthermore, these chemical domains seem to have no strong resistance to the growth of polar domains in Scdoped Pb(Mg1/3Nb2/3)O3. KeywordsFerroelectric phase transitions, Relaxor ferroelectrics, Electric fields, Transmission electron microscopy, Ceramics, Niobium, Phase transitions, Magnesium, Polarization, Grain boundaries Disciplines Ceramic Materials | Materials Science and Engineering CommentsThe following article appeared in Journal of Applied Physics 102 (2007) Sc doping in Pb͑Mg 1/3 Nb 2/3 ͒O 3 enhances the B-site 1:1 cation order significantly but promotes the ferroelectric polar order moderately. At low doping levels, the electrical polar domains remain at the nanometer scale and the relaxor ferroelectric behavior is preserved. A normal ferroelectric state can be triggered with electric fields from the relaxor state at lower temperatures. This electricfield-induced phase transition process was directly observed with an in situ transmission electron microscopy technique in a 4 at. % Sc-doped Pb͑Mg 1/3 Nb 2/3 ͒O 3 polycrystalline ceramic under different conditions. It was found that the phase transition started at the grain boundary and took two steps to complete: The gradual coalescence of the polar nanodomains and the abrupt formation of the long-range ferroelectric domains. During the growth of the polar nanodomains, the morphology of the cation ordered chemical domains does not change. Furthermore, these chemical domains seem to have no strong resistance to the growth of polar domains in Sc-doped Pb͑Mg 1/3 Nb 2/3 ͒O 3 .

Metal halide perovskites have attracted great interest in recent years and their emission wavelength can be adjusted either by doping impurities or by exploiting quantum size effect. Here, it is reported that the realization of optically‐controlled quantum size effect in a hybrid nanocavity composed of a perovskite (CsPbBr3) nanoparticle and a thin gold (Au) film. Such nanocavities are created by synthesizing polycrystalline CsPbBr3 nanoparticles composed of quantum dots on a thin Au film via chemical vapor deposition, which emit luminescence at ≈488 nm under the excitation of femtosecond laser pulses with a low repetition rate. The phase transition from polycrystalline to monocrystalline, which quenches the quantum size effect and shifts the emission wavelength to ≈515 nm, can be introduced in CsPbBr3 nanoparticles by simply increasing the laser power. Interestingly, such a phase transition is reversible provided that the laser power is lower than a threshold. Consequently, four optical states including dual‐wavelength emission, can be achieved by deliberately setting the laser power. The underlying physical mechanism is unveiled by the static and transient temperature distributions simulated for the hybrid nanocavity. The findings open a new avenue for designing novel photonic devices based on perovskite nanoparticles and plasmonic nanostructures.