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Electro‐coalescence is the fusion phenomenon between a pair or more microfluidic droplets that are immersed in an immiscible medium under an electric field. This technique is frequently used to merge confined droplets in surfactant‐stabilized microfluidic emulsions using local electric fields. Despite the necessity of miniaturized electrodes, this method has proven highly successful in microfluidics and lab‐on‐a‐chip applications. Miniaturized electrodes severely curtail the spatial and temporal flexibility of the electric potential, thus hindering real‐time and flexible operation and leading to high production costs. The current study addresses this problem with reconfigurable electric field potential by light‐driven functional virtual electrodes. These electrodes are light‐induced on a non‐centrosymmetric ferroelectric photovoltaic crystal placed below a microfluidic droplet channel. The photovoltaic effect in the crystal is responsible for the space charge distributions that act as virtual electrodes, whose evanescent field is screened by free charges into the two liquids inside the channel. A numerical model is developed to describe the evolution of the evanescent electric field causing electro‐coalescence. Based on this prediction, two coalescence processes occur at two different timescales and with different numbers of droplets involved. Controlled exposure time modulation allows either rapid on‐demand coalescence of droplet pairs or breakup of the entire emulsion. [ABSTRACT FROM AUTHOR]

Sn2P2S6, Sn2P2(Se0.05S0.95)6 and Sn2P2Se6 crystals are resistant to water, weak chemical aggressive media, and magnetic field. Model of low-temperature sensors is suggested, based on temperature dependences of the ac current. [ABSTRACT FROM AUTHOR]

Fabrication of the optical waveguide is essential for the application of high-performance relaxor ferroelectric single crystals in broadband integrated electro-optic devices. Here, a multimode titanium in-diffusion planar waveguide is demonstrated in a rhombohedral phase Pb(In 1/2 Nb 2/3)O 3 –Pb(In 1/2 Nb 2/3)O 3 –PbTiO 3 (PIN-PMN-PT) single crystal. Influences of titanium in-diffusion on the crystalline phase and composition were carefully studied. Guided modes in the planar waveguide were characterized by prism couple measurements. Using the inverse Wentzel-Krames-Brillouin method, the refractive index profile in the waveguide was constructed. The results show that the PIN-PMN-PT crystal retains its single crystal structure and excellent electro-optic response after titanium in-diffusion. The mode refractive index change between the diffused layer and substrate crystal is approximately 3%, which is sufficient to constrain the energy of transmitted light. Moreover, the titanium-diffused PIN-PMN-PT waveguide is confirmed to be a graded optical waveguide with a Gaussian index profile. Our work indicates that the titanium in-diffusion is a feasible way to fabricate waveguides in PIN-PMN-PT crystals, which is of great significance for their application in integrated photonic devices. [ABSTRACT FROM AUTHOR]

Domain switching coupled with polarization reorientation allows ferroelectrics to exhibit high potential for use in nonvolatile memories, electro-optic devices, and nanoelectronics. Although several studies have elucidated domain switching, the research on switching dynamics of complex nanoscale domain structures in relaxor-based ferroelectric materials has been lacking. Herein, the domain structure and domain switching dynamics in tetragonal PIMN-PT single crystals were systemically studied via piezoresponse force microscopy. An interlocking multi-type domain pattern comprising irregular 180° ferroelectric domains and regular 90° ferroelastic domains was observed and its formation mechanism was explored. Different domain switching dynamics of field-dependent responses were investigated. The results indicate that T-phase PIMN-PT single crystals exhibit a hierarchical domain switching process. Under a low electrical-bias stimuli (<10 V), the nucleation and growth of 180° domains dominate the switching process. By increasing the electrical bias from 10 V to 80 V, 90° domain switching was gradually completed and the sample achieved a single-domain state. The nucleation and growth mechanism of ferroelectric domains under electrical-bias stimuli were also discussed. Overall, our results deepened the understanding of ferroelectric switching in complex nanoscale domain structures and facilitate the use of precise domain tailoring technology for fabricating T-phase relaxor-based ferroelectric single crystals. [ABSTRACT FROM AUTHOR]

Synthesis conditions of Aurivillius structure Bi2MoxW1-xO6 series and the composition range of solid solution were explored by solid phase reaction method, and the flux growth system of Bi2MoxW1-xO6 crystal was explored. The structure, variable temperature dielectric property and resistivity of the crystal were measured and analyzed. Due to their large spontaneous polarization and high Curie temperatures, ferroelectric Aurivillius Bi2MoxW1-xO6 have attracted tremendous research attention in petroleum mining industries, communication equipments, meidcal ultrsonic diagnostics, structural health monitoring, et al. In this study, the composition variation range of n(Mo):n(W) ratio in Bi2MoxW1-xO6 solid solution were studied in detail through changing the sintering temperature and dewelling time. According to the synthetic results, the proportion(x) of Mo in the solid solution can be continuously tuned in the range of 0 to 1, and the pure ferroelectric phase of Bi2MoxW1-xO6 can be synthesized under different temperatures in the range of 500°C to 870°. Growth of the Bi2MoxW1-xO6 single crystals through the high temperature solution method were also explored systematically. By employing Li2B4O7 -Bi2O3 (molar ratio 2:1) as a flux, centimeter-sized Bi2WO6 single domain crystals were grown with the thickness of about 2 mm and the maximum dimension reaching as large as 40 mm. Centimeter-sized single domain crystals of Bi2Mo0.15 W0.85O6with the thickness of about 1 mm were also grown in n(Bi2O3): n(MoO3):n(WO3): n(Li2B4 O7)=1:1:1:1 (molar ratio) flux system. Structural refinement reveals that Bi2Mo0.15 W0.85O6 crystallizes into the orthorhombic system, Aba2 (No. 41) space group. Variable temperature dielectric measurements show that the dielectric constant ε33 increases from 70 of Bi2WO6 crystal to 102, and the temperature at which the dielectric relaxation occurs decreases from 430 °C of Bi2WO6 crystal to around 330 °C. The temperature varying resistivity shows that the resistivity of Bi2WO6 and Bi2Mo0.15 W0.85O6 crystals both decrease with the increase of temperature. Below 100 °C the resistivity of Bi2 WO6 is higher than that of Bi2Mo0.15 W0.85O6 crystal, and with the increase of temperature, the difference of resistivity between the two crystals is gradually narrowing. [ABSTRACT FROM AUTHOR]

Ferroelectric crystals possess good physical properties, which endow them with great potential in photovoltaic, piezoelectric, and electro-optic applications. The polarization stability of ferroelectric crystals is crucial for device applications, because their performance mostly relies on the engineering of domain structures. In this paper, we show that the polarization stability can be improved through light illumination during poling; the obtained Mn and Fe-doped KTa 1- x Nb x O 3 (Mn&Fe: KTN) single crystals maintained stable single-domain state and excellent electro-optic properties over a 1-year observation period. We propose a possible mechanism for the improved polarization stability through light-activated defect engineering, and also investigate the effect of light illumination on defect states in KTN crystals. Appropriate ions doping and light activation effect are shown to be the effective method for achieving high polarization stability after electric field poling. The light-activated defect engineering promotes the stabilization of polarization structures, which is beneficial for the development of high-performance applications based on ferroelectric crystals. [Display omitted] [ABSTRACT FROM AUTHOR]

This study investigates the ultrafast dynamics of coherent phonons and phonon-polaritons in lithium niobate (LiNbO3) crystals using reflective pumpâ€"probe spectroscopy with 25 fs time resolution. In addition to several coherent optical phonon modes, the electro-optic (EO) sampling measurements explored the coexistence of phonon-polariton E -modes near 3.8 and 14.9 THz, which agrees considerably with the theoretical phonon-polariton dispersion curves. We also discovered that a time lag ( Î" t ≈ 0.2 ps) between the coherent optical phonon and phonon-polariton originates from the coupling time for propagating phonon-polariton. Our findings provide a possible application of LiNbO3 for ultrafast EO phonon modulators with bandwidths greater than 10 THz. [ABSTRACT FROM AUTHOR]

A giant linear electro‐optic (EO) effect and high transparency in ferroelectric potassium tantalate niobate [(KTa1−xNbxO3), KTN] crystal is achieved via a thermally controlled domain engineering method. It involves a two‐step thermal annealing process: 1) a rapid cooling process that forms polar nano‐regions (PNRs), i.e., a cooling rate of 1.67 °C s−1 from Tc+58 °C to Tc+8 °C where Tc is the Curie temperature; and 2) a slow cooling process that facilitates abnormal domain growth (AGG) i.e., a cooling rate of 0.0115 °C s−1 from Tc+8 °C to Tc−15 °C. Since PNR can have a faceted boundary and high anisotropy, it can promote AGG within single crystals to realize solid‐state domain conversion macroscopically from a multi‐domain to single‐domain crystal within a slow cooling process. The resultant KTN crystal offers high transparency that is equivalent to its paraelectric phase; and a linear EO coefficient (γ51) as large as γ51≈51200 pm V−1, which is five times the value of conventional KTN crystals with similar composition. This giant linear EO coefficient represents a major technical advance in EO materials and significantly reduces the driving voltage, power, and footprint of many types of EO devices. [ABSTRACT FROM AUTHOR]

The effect of temperature and electric field on phase transitions, dielectric relaxation behavior, and macroscopic electrical performances of Pb(In 1/2 Nb 1/2)O 3 -0.49 Pb(Mg 1/3 Nb 2/3)O 3 -0.27PbTiO 3 (PIMNT27) single crystals were studied. The nanosized domains of unpoled crystals and the engineered domains of DC electric field poled crystals were intuitively recorded by piezoresponse force microscopy (PFM). The distribution of nanosized domains with different sizes and patterns induced by domain switching and domain wall motion under different poling fields and temperatures were also studied to understand the effect of nanosized domains on phase transitions, piezoelectric, and electromechanical properties. [ABSTRACT FROM AUTHOR]

• The optical temperature sensing by using ferroelectric crystal as matrix materials was investigated. • Excellent relative sensitivity was demonstrated based on 2H 11/2 and 4S 3/2 TCLs. • Comparable absolute sensitivity was also verified based on 4S 3/2 and 4F 9/2 NTCLs. The optical temperature sensing of Er3+/Yb3+-doped Pb(Sc 1/2 Nb 1/2)O 3 (PSN)–Pb(Mg 1/3 Nb 2/3)O 3 (PMN)–PbTiO 3 (PT) (6PSN–61PMN–33PT with 2- wt% Er 2 O 3 and 2- wt% Yb 2 O 3) crystal was investigated based on temperature-dependent upconversion luminescence. Apparent difference in variation of luminescence intensity with temperature was observed for different emission bands. Moreover, excellent relative sensitivity and comparable absolute sensitivity were demonstrated based on the thermally coupled levels (2H 11/2 and 4S 3/2) and nonthermally coupled levels (4S 3/2 and 4F 9/2), respectively. These findings hold substantial implications for promoting the development of ferroelectric crystals towards electric-optical integration. [ABSTRACT FROM AUTHOR]

The electrical properties and polarization fatigue of [001]-oriented 6Pb(Sc1/2Nb1/2)O3-70Pb(Mg1/3Nb2/3)O3-24PbTiO3 (6PSN-70PMN-24PT) crystals were investigated. Compared with binary Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) crystals, the ternary 6PSN-70PMN-24PT crystal showed a higher rhombohedral → tetragonal transition temperature (TR-T = 120°C) and a larger coercive field (Ec = 4 kV/cm). It was found that the piezoelectric constant (d33 ≈ 1200 pC/N) and electromechanical coupling coefficient (kt ≈ 61%) were weakly dependent on the thermal annealing temperature (Ta), maintaining over 90% of the original value at Ta < 120°C, indicating excellent piezoelectric thermal stability. Electric fatigue measurements showed that the ternary 6PSN-70PMN-24PT crystal exhibited slight fatigue characteristics below 105 bipolar cycles, while the binary PMN-PT crystal exhibited sudden polarization degradation when the cycle numbers were above 102 cycles. The improved fatigue stability for 6PSN-70PMN-24PT crystals was attributed to the large coercive field. The physical mechanisms of the enhanced coercive field and high transition temperature were discussed based on repulsive energy and polar domains. [ABSTRACT FROM AUTHOR]

Electro-optic (EO) devices with high EO coefficients at radio and microwave frequencies are integral components of the photonics industry. This work determines the EO effect of ferroelectric Li-doped niobium-rich potassium tantalate niobate (K 0.95 Li 0.05 Ta 1- x Nb x O 3 ; KLTN) single crystals using improved dynamic EO measurement. The phase transitions of KLTN crystals were investigated via variable-temperature Raman spectroscopy. A full view of the surface displacement and velocity for the KLTN sample at the resonant frequency was studied using an ultra-frequency vibrometer. The KLTN sample with x = 0.60 exhibits the enhanced effective EO coefficient (γ c ) ∼ 217 pm/V near the piezoelectric resonant peaks, which is comparable with the value at low frequency. The piezoelectric enhanced EO property of KLTN single crystals can be attributed to nonlinear polarization and nonzero stress, and showing promising for designing practical optical-piezoelectric-mechanism coupling devices. [ABSTRACT FROM AUTHOR]

This paper is devoted to investigations of ferroelectric properties of dimethylammonium metal sulphate hexahydrate DMAMe1-xCrxS (Me=Al, Ga) ferroelectric crystals in vicinity of the ferroelastic-ferroelectric phase transition. In particular, it is shown that the isomorphous substitution of the aluminium ion with chromium noticeably changes the temperature of phase transition and spontaneous polarization in DMAAl1-xCrxS. These changes are explained in terms of clusters sizes and dynamics in the framework of the order-disorder type phase transition mechanism. [ABSTRACT FROM AUTHOR]

This paper is devoted to the study of the influence of metal ion isomorphous substitution on the ferroelastic-ferroelectric phase transition and dispersion caused by the motion of domain walls in dimethylammonium metal sulfate hexahydrate DMAAl1−xCrxS ferroelectric crystals (x= 0, 0.065, 0.2). It is shown that such a substitution significantly changes the phase transition temperature and parameters of the dielectric dispersion. These changes are explained in terms of interaction between the metal-hydrate complexes and DMA groups that carry the dipole moment and due to this they are responsible for the phase transitions and motion of the domain walls. [ABSTRACT FROM AUTHOR]

The properties of phonon-polaritons in Czochralski-grown piezoelectric superlattice (CPSL), are studied theoretically. We propose the phonon-polariton mode of CPSL. The mechanism for polariton coupling is analyzed. We discuss the factors that influence the properties of the phonon-polariton. Some potential applications are also discussed. [ABSTRACT FROM AUTHOR]

Piezo-/ferroelectric crystals of Pb(Lu 1/2 Nb 1/2 )O 3 -Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 ternary solid solution system with high Curie temperature, in the vicinity of morphotropic phase boundary (MPB) region, are grown by the top-seeded solution growth (TSSG) method for the first time. The compositions and structures of the crystals are analyzed, all the structures are found to have pure perovskite structure using X-ray diffraction analysis. Di-/piezo-/ferroelectric properties of the crystals are also characterized systematically. The Curie temperature T c and coercive field E c , increase gradually with increasing PbTiO 3 content. In particular, the crystal with composition 0.34PLN-0.31PMN-0.35PT possesses excellent electric properties including the Curie temperature, the rhombohedral–tetragonal phase transition temperature, the piezoelectric coefficient, the remnant polarization and the coercive field, which are T c = 228 °C, T RT = 156 °C, d 33 = 2092 pC N −1 , Pr = 35.5 μC cm −2 and E c = 8.1 kV cm −1 , respectively, making it a promising material for transducers or detectors in a wide temperature range. [ABSTRACT FROM AUTHOR]

The polarization reversal techniques of ferroelectric optical crystals enable us to construct new high-speed microwave signal processing devices with advanced functions; wireless microwave signal discrimination for space-division-multiplexing systems, pre-equalization for signal distortion caused by fiber dispersion in long haul optical fiber communications, and so on. In this paper, potential of these new functional devices for microwave photonic systems is discussed. [ABSTRACT FROM PUBLISHER]