Reversal Current Research Articles

Removal of heavy metals from mine tailings by in-situ bioleaching coupled to electrokinetics

This work utilizes a combined biological-electrochemical technique for the in-situ removal of metals from polluted mine tailings. As the main novelty point it is proposed to use electrokinetics (EK) for the in-situ activation of a bioleaching mechanism into the tailings, in order to promote biological dissolution of metal sulphides (Step 1), and for the subsequent removal of leached metals by EK transport out of the tailings (Step 2). Mine tailings were collected from an abandoned Pb/Zn mine located in central-southern Spain. EK-bioleaching experiments were performed under batch mode using a lab scale EK cell. A mixed microbial culture of autochthonous acidophilic bacteria grown from the tailings was used. Direct current with polarity reversal vs alternate current was evaluated in Step 1. In turn, different biological strategies were used: biostimulation, bioaugmentation and the abiotic reference test (EK alone). It was observed that bioleaching activation was very low during Step 1, because it was difficult to maintain acidic pH in the whole soil, but then it worked correctly during Step 2. It was confirmed that microorganisms successfully contributed to the in-situ solubilization of the metal sulphides as final metal removal rates were improved compared to the conventional abiotic EK (best increases of around 40% for Cu, 162% for Pb, 18% for Zn, 13% for Mn, 40% for Ni and 15% for Cr). Alternate current seemed to be the best option. The tailings concentrations of Fe, Al, Cu, Mn, Ni and Pb after treatment comply with regulations, but Pb, Cd and Zn concentrations exceed the maximum values. From the data obtained in this work it has been observed that EK-bioleaching could be feasible, but some upgrades and future work must be done in order to optimize experimental conditions, especially the control of soil pH in acidic values.

Enhanced Methanol Oxidation in Alkaline Media on Electrodeposited Ni Electrodes by Morphological and Crystallographic Evolution

This research aims at exploiting the electrocatalytic behaviour of nano-crystalline nickel electrodes electrodeposited by different techniques including direct current (DC), pulse current (PC), or pulse reversal current (PRC) for methanol electrooxidation in alkaline solutions. We understand that PC electrodeposition forms pyramidal shaped grains with a preferential Bragg diffraction peak of (111), whereas PRC produced refined spherical grain morphology with a strong (200) diffraction peak. However, DC electrodeposition exhibits an intermediate morphology and crystalline structure. Cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) show that PRC electrodeposition develops Ni electrodes with better electrocatalytic activity for methanol electrooxidation than other two nickel electrodes. Based on the CV curve, the current density for Ni prepared by PRC electrodeposition methods is about 75.26 mA.cm−2, which is higher than those of DC and PC methods. This higher activity of PRC electrodeposited nickel is attributed to the low charge transfer resistance confirmed by Nyquist plots. We attributed this behavior to the (200)-oriented crystallographic texture, spherical grain morphology, and consequently the high electrochemical active surface area of this nickel electrode. This work reveals the importance of surface morphology and crystallography on the electrocatalytic behaviour of nickel electrodes for electrochemical energy devices.

The Hydrostatic Buckling of SPM Systems of Fish Cages and a Design Method to Prevent It

This study presents an inherent buckling issue of SPM (Single Point Mooring) systems for open sea aquaculture and a design method to analyze and solve this issue. The SPM arrangement of a row of cages is very efficient, as it minimizes the anchoring load by masking of the current applied to the downstream cages, hence saves anchors and mooring lines. However, a sudden reversal of the current direction presents a risk of buckling of the row of cages, if it applies a compression load along the array of cages before rotation of the entire cage system takes place. This study presents the concept of Hydrostatic Buckling of a row of cages and a method of design and analysis to control the stability of the system at the situation of sudden current reversal. First, a simple method for preliminarily assessment by applying the principle of virtual work is formulated. Then, an analysis of the structure by a parametric finite elements code is presented. The reversal current limits for the stability of the structure, are parametrically studied, by the analyses of two hypothetical practical scenarios. This study presents practical design tools and results, such as the method of the analysis, simplified loading states for representing the critical events, the scantlings of the structure, as well as guidelines for designing a SPM system of cages that withstand critical situations of reversal current.

Simulated circulation and particle trajectory analysis related to the oil spill event in the Karawang Coastal Waters

The Karawang waters are situated at the north coast of West Java Province, where the wind-driven monsoonal current controls significantly the dispersion of oil spill. Here accident of oil spill was happened on 12 July 2019. The present study aims to simulate seasonal circulation and particle trajectory analysis related to oil spill dispersion, by performing a fine-resolution 1/96° coastal circulation model of CROCO. The model is validated SST (Sea Surface Temperature) detected form satellite, sea level, and surface current with high correlation (corr.>0.86). The Sentinel-1A imagery determined initial position of oil spill. Seasonal reversal currents are reproduced well by the model, consistence with past studies. The westward flows along the northern coastal area during the southeast monsoon (SEM) bring colder and saltier seawater. In contrast, the eastward flows during the northwest monsoon period, associated with warmer and fresher seawater. The massless particles related to oil spill dispersions are advected by the current westward along the coastal area. About one week after the accident, the oil spill closed to the Tanjung Karawang waters, where particle trajectories overlay with the observed Sentinel imagery. The model suggested that on 24 July 2019, particle trajectories released from oil spill accident arrived offshore Jakarta Bay.

Mist-CVD-derived Hf0.55Zr0.45O2 ferroelectric thin films post-annealed by rapid thermal annealing

We have newly applied Rapid Thermal Annealing (RTA) for the post-annealing of mist chemical-vapor-deposition (CVD)-derived Hf1−xZrxO2 (HZO) thin films. A ferroelectric polarization-electric field (P–E) curve was confirmed typically with noticeable polarization reversal currents. These ferroelectric properties of the HZO thin films provided quantitative estimation for Pr and Ec of ∼20 µC/cm2 and 1–1.5 MV/cm, respectively, compared to those reported from other growth methods, such as atomic-layer-deposition (ALD). It was revealed that the background leakage should be further reduced in a mist-CVD HZO film compared to those by ALD recently reported. The origin of the leakage was strongly related to the oxygen vacancy (Vo) generated in the film and near the HZO/bottom electrode interface. Nonetheless, it was found effective to use atmospheric pressure in air or oxygen in the post-RTA process for reducing leakage. In general, endurance behaviors for the mist-CVD HZO film revealed similar to those for samples prepared by other methods for both “wake-up” and “fatigue” phenomena, showing that the mist-CVD HZO film endured up to 2 × 109 counts. Finally, we expect that the mist-CVD HZO thin film would become a candidate for fabricating large-scale integration-oriented ferroelectric devices due to the intrinsic merits of the method.

Co-precipitation synthesis of LaFe1-xAlxO3 (x = 0–0.2) on structure and electromagnetic properties

The synthesis of LaFe1-xAlxO3 (x = 0–0.2) on the structure and electromagnetic properties using the co-precipitation method were evaluated. LaFe1-xAlxO3 (x = 0–0.2) materials were synthesized using lanthanum chloride and natural iron sand powders. The mixing process of precursors was held with a hotplate temperature of 60 °C. The calcination process was done at 400 °C for 2 h. Then samples were analyzed using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Vibrating Sample Magnetometer (VSM), and CV meter. The XRD patterns result in two phases of LaFeO3 and Fe2O3. SEM images were performed that the powders are porous agglomerates. The particle size distribution is shown in the histogram that the samples are in the range of 50–500 nm, respectively. Then, the magnetic properties measurement of VSM analysis studied the substitution of Fe to Al ions decreases magnetic properties and BHmax in LaFe1-xAlxO3 (x = 0–0.2). The I-V measurements conducted the substitution of Fe to Al ions increase with a nonlinear reversal current in LaFeO3. These results show that LaFe1-xAlxO3 (x = 0–0.2) was recommended as the magnetic permanent material and perovskite material based on electromagnetic properties.

Effect of low voltage limit on degradation mechanism during high‐frequency dynamic load in proton exchange membrane water electrolysis

With regard to the hydrogen economy, setting the criteria for the durability evaluation of renewable energy-powered proton exchange membrane water electrolysis (PEMWE) systems is an important milestone. In this study, accelerated stress test (AST) protocols that simulate the fluctuating power supply of renewable energy were explored. The average load was varied by changing the low voltage limit (LVL = 1.4, 1.5, 1.7, and 1.9 V) with fixation of a high voltage limit of 2.2 V. AST protocols can accurately reflect the real solar profile with various loads and high ramp rates. Protocols with the LVL = 1.4 V and LVL = 1.5 V demonstrated opposite trends even with minimal difference in LVL, resulting in positive and negative degradation slopes, respectively. The positive degradation slope (meaning performance decrease) for LVL 1.4 V is attributed to the reversal current, resulting in degradation of the cathode catalyst, which is characteristic of the fuel cell operating mode. On the contrary, a slight performance increase was observed for LVL 1.5 V, presumably caused by the thinning of the membrane and the creation of a rougher surface in the anode/membrane interface. Meanwhile, protocols with higher LVL (LVL 1.7 V and LVL 1.9 V) showed significant mass transport loss observed at voltages larger than 1.8 V. This may be attributed to severe delamination of the catalyst/membrane and/or diffuse layer/catalyst interface, presumably due to the changes in bubble nucleation and the resulting stress. The findings suggest a rational guideline for establishing a unified AST protocol applicable to renewable energy-powered PEMWE systems, and subsequent material development strategies to minimize degradation processes.

Unidirectional current-driven toron motion in a cylindrical nanowire

A magnetic toron is a spatially localized three-dimensional spin texture composed of skyrmionic layers with two Bloch points at its two ends. The magnetic toron can, thus, be stabilized in chiral magnets using external fields. In this work, we studied the toron dynamics induced by electric currents in a cylindrical nanowire using micromagnetic simulations. We show that the toron performs a unidirectional motion in a nanowire where the current is applied along the wire direction. The current-induced toron motion can be divided into three regions: static region for a small current due to the pinning effect, toron moving region for a large current, and toron annihilation region for a large reversal current. Moreover, the moving direction can be tuned by the sign of Dzyaloshinskii–Moriya interaction. Such peculiar dynamics indicates that the magnetic toron is a possible candidate as an information carrier.

Near-electrode polarization and determination of the mobility of intrinsic charge carriers in PVDF films

The process of near-electrode polarization in a polyvinylidene fluoride (PVDF) film was studied using reverse currents Irev(t). It was proven that the maxima on the Irev(t) curves are characteristic of near-electrode polarization. The dependences of the reversal currents on time were analyzed based on various representations. The mobilities of the intrinsic charge carriers in the film and the magnitude of the charge transferred through the dielectric layer from electrode to electrode were calculated. The conductivity of PVDF was studied and analyzed in the temperature range 90°C-130°C.

Ratchet motion and current reversal of Brownian motors coupled by birth-death interactions in the crowded environment

In this study, we investigate the ratchet transport behaviors of coupled Brownian motors with stochastic interactions in the crowded environment, which is characterized by two parameters, including particle concentration and interacting stability. Thus stationary birth-death process is employed to describe the process of fluctuating particles in the coupled system, and it is a more realistic and accurate description than the conventional variable-mass systems on stochastic phenomena of absorbing and desorbing particles in some complex mediums. It is found that the stochastic interactions could induce the normal or reversal current by influencing the asymmetry and barrier height of effective ratchet potential, and in strong-coupling regime, the dynamical mechanism could be well interpreted. By the numerical simulations, we systematically study the dependence of directed current, stochastic resonance (SR) and coherent resonance (CR) behaviors of transport velocity on various parameters, including particle concentration, interacting stability, coupling strength, spring’s free length, driving amplitude, ratchet asymmetry, and medium temperature. The results also provide the latent support for manipulating transport behaviors and optimizing the coupled structure in artificial nanomachines.

Investigating the Nonlinear Effects of Magnetization Reversal and Eddy Currents in the Rotors of Hysteretic Electromechanical Energy Converters

A way of constructing the static and dynamic magnetization curves of the volume of a magnetic material is described. The procedure allows the conditions of the existence and parameters of weak and strong electromagnetic fields in such materials can be described accurately. A rigorous solution of the nonlinear equation relating the change functions and the magnitude of the induction and intensity of the dynamic magnetization curves is found.

Comparison Between the Constant Dummy Load and Step Load Shut‐Down Strategy for PEMFCs

AbstractCarbon corrosion of catalyst layer (CL) caused by start‐up/shut‐down (SU/SD) conditions in proton exchange membrane fuel cells (PEMFCs) decreases the durability of the membrane electrode assembly (MEA). It is reported that the dummy load shut‐down strategy helps alleviating the carbon corrosion. In this paper, constant load strategy and step load strategy are applied during 900 SU/SD cycles each, to investigate the effects of different dummy load forms on the durability of PEMFC. Reversal current is observed during the last phase of 5 A constant loading process, while there is no reversal current during the step load strategy. The results obtained through polarization curves, cyclic voltammetry (CV) and scanning electron microscope (SEM) technologies, prove the step load strategy more efficient to alleviate the performance decay. Therefore, the step load strategy can improve the durability of PEMFC.

Optimizing the electrode surface area of sediment microbial fuel cells.

Sediment microbial fuel cells (SMFCs) is a promising technology for bioremediation, environmental monitoring and remote power supply in various water environments. Optimizing the anode/cathode surface area ratio (SARa/c) is important to enhance the power and decrease the cost of SMFCs. However, in fact, little information has been reported to optimize the SARa/c of SMFCs in individual or stacked mode. This study comparatively analyzed the effects of electrode surface areas on the performance of single SMFCs and serial SMFC-stacks under separated- and connected-hydraulic conditions. The results suggested an optimal SARa/c of 1 to 1.33 for both single and serial stacked SMFCs. Voltage reversal occurred in serial SMFC stacks with unoptimal SARa/c but not in optimized stacks. The more the SARa/c deviated from the optimal SARa/c, the more easily the voltage reversal occurred (i.e. lower reversal current). Compared to a separated-hydraulic environment, a connected-hydraulic environment showed no effect on the power generation of anode-limiting SMFC stacks but decreased the power generation and reversal current of cathode-limiting SMFCs, probably due to larger parasitic current. The results are important for the scale-up and application of SMFCs.

Transient Cell Reversal Due to Anode Hydrogen Starvation in PEM Fuel Cells - Experimental and Modeling Study

Due to the significant development work by major automotive OEMs, fuel cell electric vehicles (FCEVs) have become much closer to a commercial reality. While the overall system cost reduction is still much needed to warrant commercial success, further improvement in system robustness could ensure better customer experience and wider market adoption. Certain automotive fuel cell operations, e.g., cold/freeze start-up, idling at low power, start-up after long shut-down periods, can lead to conditions that produce fuel cell damage if not managed properly. Drawing power under such conditions can sometimes lead to hydrogen starvation in certain cells of a stack, which can cause the cell voltage to become negative (i.e., cell reversal), leading to anode carbon corrosion and electrode damage.1 Depending on the nature of the root cause and the system control strategy, the reversal events can last from less than 1 second to a few minutes. Though relatively longer cell reversal (minute to tens of minutes) has been often reported and well understood,2 study on transient cell reversal (<1 second) has been rare. In this work, we use a 53-cm2 single cell to study cell reversal events that last 1 second or less and investigate actual anode damage both experimentally and by modeling. Anode hydrogen starvation was created by maintaining a constant hydrogen flow into the anode, while stepping the current density from 0.02 A/cm2 up to 0.6 A/cm2 for a given time (e.g., 1 second). The hydrogen flow is sufficient for 0.02 A/cm2, but is less than the stoichiometric requirement at 0.6 A/cm2. Fig.1 shows cell voltage and current transient profiles during a cell reversal event. It is seen that cell voltage drops from 0.87V to -0.96V when the current density was increased from 0.02 A/cm2 to 0.6 A/cm2. The anode H2 flow was kept constant at 0.3 stoics at 0.6 A/cm2 current density. Upon the increase of current density, cell voltage drops quickly to a first plateau at ~0.65V (Fig.1), which is believed to be due to polarization of cathode oxygen reduction reaction (ORR), while H2 in the anode compartment can still sustain the current for a very short period of time. After this initial plateau, cell voltage drops precipitously to a second plateau at ~-0.96V, where oxygen evolution reaction (OER) as well as carbon oxidation reaction (COR) are sustaining the reversal current (0.6 A/cm2). Although H2 is still being fed to the anode at a flow rate of 67 sccm, the hydrogen oxidation reaction (HOR) has been deactivated due to an oxidized Pt surface at elevated anode potential, which was corroborated by the H2 concentration measurement in anode exhaust using the high-speed mass spectrometer. Furthermore, due to the fast change in voltage, the capacitive current (due to double-layer capacitance) and pseudo-capacitive current (due to desorption Pt-H and formation of Pt-OH) also contribute to the overall reversal current. Thus, the true damage to anode during transient cell reversal has to be accessed by taking into account of oxidation of available hydrogen, the capacitive and pseudo-capacitive current, as well as the oxygen evolution reaction. A kinetic model was, therefore, developed to describe the transient cell reversal by considering the above kinetic and capacitive current contributions. The model was built based on the conservation of charge which couples with hydrogen transport from flow-field to the anode catalyst layer during the transient process. It adopts the Pt-oxide growth model for the evolution of Pt-oxide coverage,3 and utilizes the previously measured kinetics for the relevant electrode reactions.3-4 Additionally, hydrogen oxidation reaction is made to be impeded at high electrode potentials, corresponding to the experimental observation. The resulting model equations are solved for transient anode potential, Pt-oxide coverage, and contributing reaction currents under a given cell reversal condition. In this presentation, we will discuss the details of both the experimental and modeling work in understanding the contributors to the overall reversal current during a transient cell reversal event. References P. T. Yu, W. Gu, J. Zhang, R. Makaharia, F. T. Wagner, and H. A. Gasteiger, Polymer Electrolyte Fuel Cell Durability, F. N. Buchi, M. Inaba, and T. J. Schmidt, Editors, Springer, New York, NY, 2009. T. R. Ralph, S. Hudson, and D. P. Wilkinson, ECS Trans., 1 (8), 67 (2006). S. Arisetty, Y. Liu, W. Gu, and M. F. Mathias, ECS Trans., 69 (17), 273 (2015). W. Gu, P. T. Yu, R. N. Carter, R. Makharia, and H. A. Gasteiger, Modeling and Diagnostics of Polymer Electrolyte Fuel Cells, Modern Aspects of Electrochemistry 49, U. Pasaogullari, C.-Y. Wang, Editors, Springer, New York, NY, 2010. Figure 1

A comparison between size dependent paraelectric and ferroelectric BaTiO3 nanoparticle doped nematic and ferroelectric liquid crystals

The electro-optic and dielectric properties of barium titanate, BaTiO3, and nanoparticle (NP) doped nematic and ferroelectric liquid crystal materials were examined with respect to different size and concentrations of the NPs. Smaller size paraelectric NPs (≈80 nm) are compared to larger, ferroelectric NPs (≈240 nm). It is found that for concentrations larger than 0.5 vol. %, the ferroelectric NPs exhibit an increasing effect on the electro-optic response of the nematic liquid crystal, which is demonstrated by the enhancement of the dielectric anisotropy. This could be induced by the coupling of the electrical dipole moments in the spherical NPs with the LC director field. The electro-optical properties of the SmC* phase, such as the tilt angle Θ, switching time τs, and spontaneous polarisation Ps, are found to be independent of the concentration and size of the NPs. The rotational viscosity η calculated from response times, polarization reversal current, and dielectric properties is comparable for all three methods employed and practically independent of particle concentration and size. The relaxation frequency fR of the Goldstone mode is higher in the ferroelectric NPs suspensions of 2.0 vol. % as compared to the smaller paraelectric NPs.

Magnetization reversal and precession in spin valve structures with a perpendicular free layer and a tilted polarizer layer

Spin-transfer effects induced by spin-polarized current in the spin valve structures present a platform for studying different static and dynamic magnetization states sustained or driven by current. Especially, it can excite some new magnetic states and cause magnetization reversal and precession, which offers some promising applications in data processing and microwave emission. However, most of researches so far have focused on the spin valve structure with parallel or perpendicular anisotropy. Compared with the spin valve structure with parallel or perpendicular anisotropy device, the spin valve structure with a tilted polarizer is also hopeful for its potential application in fast-switching and high-density magnetic recording. Moreover, the tilted polarizer provides a new way to control the spin torquedriven magnetization dynamics in spin valve structure. In this paper, the magnetization reversal and precession driven by the spin-transfer torque in spin valve structures with a perpendicular free layer and a tilted polarizer layer are investigated theoretically. By linearizing the Landau-Lifshitz-Gilbert equation including the spin-transfer torque, two coupled dynamically evolutive equations and new equilibrium directions are obtained. Performing stability analysis for all new equilibrium directions and taking [Co/Ni]4 multilayers as an illustrative example, we obtain the phase diagrams of magnetic states defined in parameter space spanned by external magnetic field and current density. Several magnetic states, including quasi-parallel stable states, quasi-antiparallel stable states, out-of-plane precession, and bistable states are distinguished in the phase diagrams. Through adjusting the magnitudes of current density and external magnetic field, the switching from stable states to precessional ones and the reversal between two stable states can be realized, and the reversal current increases with the external magnetic field increasing. Meanwhile, we portray the phase diagram of magnetic states defined in parameter space spanned by current density and the direction of tilted polarizer. In this case, the out-of-plane precession does not emerge as the current density and external magnetic field are relatively small. Affected by the directions of spin polarizer, the reversal current of magnetization is lowest when the direction of spin polarizer is parallel to the easy axis of free-layer, and is largest when the direction of spin polarizer is perpendicular to the easy axis of free-layer. Selecting the different directions of the polarized-layer magnetization provides an alternative way to improve the efficiency of current-driven microwave emitting and magnetization reversal. By solving temporal evolution equations numerically, the behaviors of different magnetic states are shown and the validities of the phase diagrams are confirmed.

Current Limit Strategy for BLDC Motor Drive With Minimized DC-Link Capacitor

Brushless dc motor drive system employing minimized dc-link capacitor is becoming popular for the reason of compactness and long lifetime. However, once the capacitance is reduced, reversal dc-link current will lead to excessive voltage rise in the dc link when conventional current limit strategy is used. In order to avoid the damage caused by oversize pumping-up voltage, a novel current limit strategy without reversal dc-link current is necessary. In this paper, the traditional all-turn-off current limit logic is replaced by half-turn-off logic. Then, an improved current sampling scheme is presented to replace the cycle-by-cycle mode, which induces failure of current limiting after the elimination of reversal current. Finally, the proposed strategy is verified by simulation and experiment.

Switching of charged inverse micelles in non-polar liquids

The electrodynamics of micellar ions in nonpolar liquids are well understood for the case that a voltage is applied or switched off. In this work, the electrodynamics of charged inverse micelles (CIMs) are studied when the applied voltage is switched to the opposite polarity, which is relevant for applications such as electrophoretic displays and liquid toner printing. Transient current measurements are used to characterize the switching of CIMs formed in a solution of surfactant polyisobutylene succinimide in n-dodecane. For reverse voltages with amplitude below 10V the measurements are in good agreement with a drift and diffusion model, confirming the established understanding of CIMs in nonpolar liquids. When the charge content is high, the reversal current shows a characteristic peak which is explained on the basis of dynamic space-charge effects. However, for reverse voltages larger than 10V, the transient currents are influenced by electrohydrodynamic flow in the liquid causing the CIMs to switch faster than predicted by the model. The occurrence of electrohydrodynamic flow is verified by optical tracking of tracer particles. Also, when the polarizing voltage is applied for longer times, an additional current peak emerges which is due to the accumulation of newly generated charges at the electrodes.

Energy-efficient spin-transfer torque magnetization reversal in sub-10-nm magnetic tunneling junction point contacts

Spin-transfer torque (STT) magnetization reversal in a magnetic tunneling junction (MTJ), Ta/CoFeB/MgO/CoFeB/Ta, built on the tip of a nanoprobe in a direct contact with a copper substrate is demonstrated in the previously unexplored sub-10-nm diameter range. With the contact resistance of the order of 185 kOhm, the measured magnetoresistance value was 29 %. The average STT reversal current of 95 nA indicated a switching current density of approximately 0.1 MAcm−2 which is more than 30 times smaller than the smallest value reported for STT-MTJs of larger dimensions. An atomistic-scale theory confirmed the experimental result which indicates at least an order of magnitude reduction of the spin damping in the sub-10-nm diameter range.

Dielectric and electro-optic behaviour of two chiral compounds and their antiferroelectric mixtures

Dielectric and electro-optic properties of two chiral compounds (MHPOBC analogues) and their three antiferroelectric mixtures have been studied. Mixtures of both compounds show SmA*, SmC*α, SmC* and an induced antiferroelectric phase, which is not present for pure substances. All materials were studied using differential scanning calorimetry, frequency domain dielectric spectroscopy and the reversal currents method. Spontaneous polarisation of the mixtures is between 200 and 280 nC/cm2; in the antiferroelectric phase it depends linearly on temperature. Ferroelectric and antiferroelectric phase of mixtures display a mono-domain texture grown in a strong electric field upon slow cooling from the SmA* phase. In the SmC* a domain mode was observed under the bias field, while the antiferroelectric phase shows two characteristic dielectric relaxation processes that are weakly bias field dependent. The low frequency relaxation is not a single Debye-type process, and it also shows up without a bias field. The dielectric data will be discussed based on the Parry-Jones–Elston theory.