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Antiferroelectric materials are proposed as a potential solution to achieve multi-state memories, but the fundamental physical mechanism underlying the memory effect still needs to be clarified. Here, we study the memory effect in a typical antiferroelectric ceramic of Pb0.99Nb0.02[(Zr0.6Sn0.4)0.95Ti0.05]0.98O3 by systematically analyzing various hysteresis loops of polarization intensity and current density vs. electric field, where the kinetic behaviors are concerned about for the first time. The parallel pre-poling electric field reduces the critical electric field of antiferroelectric-ferroelectric phase transition, while the antiparallel field increases it. The memory behavior is significantly enhanced with the increasing of pre-poling time, but exhibits a remarkable weakening with the relaxation time increasing. It is a combined effect of electric-field-induced preferentially oriented antiferroelectric domains and internal bias electric field. This work not only improves comprehending in memory effect in antiferroelectric materials, but also enlightens the deeper understanding of other physical properties related to field-induced phase transitions.

The phase composition and their evolution in ferroelectrics are very complex near the morphotropic phase boundary (MPB), especially under multiple fields of electric field and temperature, which results in versatile behaviors of electrocaloric effect (ECE). This paper systematically studied the phase transitions and associated ECEs in the 〈001〉, 〈011〉 and 〈111〉 oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-30PT) single crystals with the chemical composition in the MPB area. Based on the dielectric and polarization responses under multi-fields, the refined electric field-temperature phase diagrams are established, wherein the ECE properties are closely related to the electric-field-induced phase transitions and exhibit a complex evolution across positive and negative values. The negative ECE originates from the transition from a monoclinic phase to a tetragonal or orthogonal phase under the noncollinear electric field, so it only appears in the 〈001〉 or 〈011〉 oriented crystals. Conversely, the transition from the tetragonal phase to the rhombohedral or orthogonal phase in the 〈111〉 or 〈011〉 oriented crystals induces a positive ECE peak with ∆Tmax = 0.40 K (@10 kV/cm). Just above Tm, the positive ECE reaches ∆Tmax = 0.61 K, 0.63 K and 0.68 K in the 〈001〉, 〈011〉 and 〈111〉 oriented crystals, respectively. In addition, there is an abnormal net endothermic phenomenon around the monoclinic-tetragonal or monoclinic-orthogonal phase boundaries due to the electric-field-induced irreversible transition.

Electron beam melting was utilized to investigate the behavior of carbon flow by melting 100 g of multi-crystalline silicon in an electron beam furnace for five minutes. Carbon and nitrogen are the constituent impurities in contaminated Si samples with an average weight of 13 % and 9, respectively. The electron beam melting experiment caused redistribution of the impurities along the periphery and bottom of the Si sample with a pie-shaped structure. Investigations through scanning electron microscopy and energy dispersive X-ray spectroscopy confirmed that the impurities were silicon nitride and silicon carbide. It was determined that Si3N4 has a rod-shaped microstructure, whereas SiC has a granular morphology. By segregating the impurities redistributed through this technique, pure Si was obtained in the remaining sample.

Removal of boron from silicon is a tough task by traditional directional solidification and vacuum refining techniques, due to its large and inappropriate segregation coefficient and low saturated vapor pressure. At high temperature boron react with oxygen to form volatile boron oxides which can be evaporated. So, the removal procedure of boron from silicon melt is investigated by incorporating a small amount of water vapor above the melted surface. The results show that boron is oxidized to mainly form BO and evaporated with 28% removal efficiency by average. It is considered that oxygen atoms experience a series of physical and chemical processes, such as a chemical reaction in the bulk of the melt, evaporation from the melt surface, transportation across the gas phase and ionization due the electron beam, which is conducive to the continuous removal of boron.

Electrocaloric effect (ECE) in ferroelectric (FE)/antiferroelectric (AFE) materials offers a promising high-efficient and zero-emission solid-state cooling technology, whose materials design is usually focused on the morphotropic phase boundary (MPB) between two FE phases. This work constructs an MPB between an orthorhombic AFE and a rhombohedral FE phase in Pb

Carbon and their compounds were removed successfully through electron beam melting (EBM), so that those areas (contaminated with carbon) of ingot were recycled and reused. During EBM process, the numerical simulation results show that there is great temperature gradient existing in the melt. During EBM, the melt near copper crucible shows low temperature and bad fluidity. Carbon in silicon melt flows, precipitated and gathered in this area so that it is separated. The flow mechanism of SiC in silicon melt was investigated. After EBM, carbon enriches in the form of SiC at the bottom of the ingot but not in the center. This technology is applied on industrial scale EBM equipment. The results show that a majority of SiC was deposited in the bottom of the refining crucible and the carbon contaminations are not found in the most of the area of the solidified ingot in crucible.

The electrocaloric effect (ECE) in the ferroelectric ceramics is determined by both the composition and the microstructure. This paper demonstrated the influences of the microstructure features on the ECE in BaTiO 3 ceramics. When the sintering temperature rises, the particles are fused together, the grain size is enlarged and the pore amount decreases, so the ECE ΔT max increases significantly. If the sintering temperature further rises to 1300 °C, the intergranular pores transform to intragranular, so the ΔT peak is enhanced but the value other than the peak is reduced. The ΔT max lowers slightly since the amount of intragranular pores gradually reduces after a second sintering for long time. The clarification of the influences of the microstructure features is instructive for the ECE material design for practical applications.

This paper demonstrated the thickness dependence of electrocaloric effect (ECE) in Ba0.8Sr0.2TiO3 ferroelectric ceramics. The high-temperature sintered sample has inhomogeneous properties along the thickness direction although the microstructure has uniform features throughout. The core zone exhibits a much lower resistivity than that of the whole sample because of more ions' valence variation. Under a same electric field of 30 kV/cm, the ECE ΔT drops from 1.35 K to 1.12 K by reducing the thickness step by step. But the thinnest core sample can sustain much higher electric fields (>50 kV/cm) and exhibits a larger ΔT of 1.67 K, i.e. it has a high ECE value despite a low ECE strength.

A new method for SiC elimination from multicrystalline silicon with Al addition by using the chemical reaction between Al and SiC is conducted in this study. Inclusion-free region is obtained when Al addition content increases to 5.4% and 7.9%. SiC particles tend to pile up around Al during the process and precipitate at ingot bottom. Furthermore, Al-Si alloying occurs at the inclusion-free region. The electron probe micro analysis mapping illustrates the existence of carbon in the precipitated Al which indicates the occurrence of chemical reaction between SiC particles and Al during the process. The results can be an effective way to eliminate SiC for silicon scraps recycling.

This paper demonstrated the electrocaloric effect (ECE) in BaTiO 3 ceramics with Ce doping in either A or B sites, which were prepared by the solid-state reaction method. All sintered samples have pure perovsikte phase, whether Ce doping in A or B sites, but the properties are different from each other. For A-site doping of Ba 1-x Ce x TiO 3 , the Curie temperature gradually shifts to lower temperature because the doped Ce ion have smaller radius than Ba ion, while the phase transition is diffused and the latent heat drops. Then the ECE ΔT peak shifts accordingly and ΔT max reduces gradually except small Ce doping. For B-site doping of BaCe x Ti 1 -x O 3 , the phase transition is diffused more significantly but the Curie temperature hardly moves, so that the ECE peak is depressed but does not shift.

A large amount of silicon in the form of silicon scraps is wasted annually in photovoltaic industry because of the presence of silicon carbide inclusions. Silicon carbide inclusions must be eliminated so that silicon scraps can be recycled. This study investigated the electromagnetic separation of silicon carbide inclusions in multicrystalline silicon by imposition of supersonic-frequency magnetic field. Silicon carbide particles tend to migrate to the ingot side and to the top and bottom of the central region of the ingot under increasing holding time. During separation process, the penetrating aluminum can react with silicon carbide and then dissolve some of the inclusions. In this work, the separation efficiency reaches up to 89.3% at a holding time of 45 min. This method is a potentially effective means of recycling silicon scraps.

The behavior of boron redistribution in silicon with and without oxide layer after electron beam injection (EBI) was investigated. Special defect shapes were generated on the surface of bare and oxidized silicon wafers. Secondary ion mass spectrometer was used to measure the boron profile. The results showed that after long EBI time, boron tended to be induced from both sides of the transition region between the oxide layer and silicon. For the sample without oxide layer after EBI, boron tended to diffuse towards the surface and its concentration obviously reduced inside the silicon. The results of the study show the potential use of the process in removing boron impurity in silicon.

Relaxor ferroelectrics continue to attract great attention for applications, including electrocaloric refrigeration, but the commonly used, indirect method of electrocaloric characterization based on the Maxwell relation often leads to artifacts. This analysis of long- and short-range ferroelectric order and the electrocaloric effect in Pb${}_{0.91}$La${}_{0.06}$Zr${}_{0.8}$Ti${}_{0.2}$O${}_{3}$ uses both direct and indirect characterizations, to clarify the applicability of the Maxwell relation to the physics of the relaxor, and the origin of discrepancies. It also suggests how to design relaxors with large electrocaloric effect by exploiting the transitions between polar nanoregions.

The development of photovoltaic industry demands great amount of multicrystalline silicon. Carbon and SiC in silicon need to be contained in a limited amount since they can cause great adverse affect to solar cells. The behavior of carbon and its precipitation SiC in silicon by electron beam melting (EBM) with a slow cooling pattern was investigated in this study. SiC is found to sedimentate to ingot bottom after EBM. The presence of Si 3 N 4 can be heterogeneous nucleation agent for SiC to nucleate continually and both of them precipitate to the ingot bottom. The comprehensive effect of slow solidification condition, temperature gradient and melt convection causes the sedimentation of SiC. It is also found that oxygen plays an important role on the migration of the dissolved carbon. The formation of carbon-oxygen complexes tend to migrate to ingot top since oxygen can transfer from silicon melt to vacuum environment during EBM.

Ferroelectrics are promising candidate materials for electrocaloric refrigeration. Materials with a large electrocaloric effect (ECE) near room temperature and a broad working temperature range are getting closer to practical applications. However, the enhanced ECE is always achieved under high electric field, which limits their wide cooling applications. In this paper, the phase diagram of lead-free BaHf x Ti 1−x O 3 (BHT) ferroelectric ceramics was established. A large ECE under relatively low electric field ( ΔE = 10 kV/cm) is firstly reported in BHT ferroelectric ceramics. The direct temperature change ( ΔT = 0.35 °C under 10 kV/cm) in BHT ceramics is comparable with those reported in the literature under high electric fields. Meanwhile, the electrocaloric efficiency ( ΔT/ΔE = 0.35 K mm kV −1 under 10 kV/cm) is thirteen percent higher than the best value reported previously under high electric field ( ΔE = 145 kV/cm). We demonstrate that the ECE can be greatly enhanced by tuning the composition of the lead-free BHT ceramics to its first-order phase transition (FPT), invariant critical point (ICP) or diffuse phase transition (DPT). It is shown that the enhancement in ECE is strongly dependent on the nature of structural phase transition and electric field coupling effect, which has been confirmed by both the indirect and direct ECE measurements. A phenomenological explanation based on Landau model was also proposed to understand this phenomenon. Our findings in this work may provide a better understanding and design methodology for developing more practically useful electrocaloric materials.

The recycling of Si scraps has become a serious concern in the industry because of the increasing amount of Si waste generated during ingot production. In this work, an operative method is proposed to process Si scraps and separate SiC from Si by coupling electromagnetic field melting with Al/SiC wetting and interaction. This method yields an inclusion-free SiC particle-enriched region that tends to migrate to the top of ingots with increasing melting time. A micron-grade SiC-rich layer is formed at the ingot edge. A petal-shaped SiC particle group is formed by Al addition and precipitates at the bottom of the ingot. A separation efficiency of 88.1% is obtained after melting for 45 min. The results show that the proposed process is an effective way to eliminate SiC from recycled Si scrap.

In this paper, alternating electromagnetic field and directional solidification are used to separate SiC and Si3N4 in polycrystalline silicon tailings. It is found the inclusion particles move downward at the center of the ingot and moving upward at the edge of the ingot by a variety of forces during the directional solidification process. The electromagnetic force accelerates the melt flow and enhances the lift force, so that larger particles can be pushed to the top of the ingot. Rod-shaped Si3N4 and block-shaped SiC particles show symbiotic relationship between each other. The aggregation of inclusion particles adsorbs metallic impurities, especially volatile metals, due to the effects of mushy region and short-circuit diffusion. The average conversion efficiency of the solar cells (Al-BSF method) prepared using the recycled silicon reached 18.56%, which meets the demand of the solar cells.

This paper demonstrated the flexible control of positive and negative electrocaloric effects (ECEs) in ⟨001⟩-Pb(Mg1/3Nb2/3)0.7Ti0.3O3 single crystal, and a dual cooling cycle is proposed using their combination to improve cooling capacity. The ECE exhibits a complex evolution of positive-negative-positive within 20–140 °C, where the negative ECE originates from the electric field-induced transition from rhombohedral phase to high-symmetric tetragonal phase. Since the coexistence of different ECEs at some temperatures, the positive and negative ECEs alternately appear in neighboring cycles under proper applied fields, i.e., dual cooling. A significant improvement of ∼150% in cooling capacity is directly characterized by the isothermal heat flow measurement.

This paper demonstrated the electrocaloric effect (ECE) of (Na0.52K0.48-x)(Nb0.92-xSb0.08)O3-xLiTaO3 lead-free ceramics by direct differential scanning calorimetry measurement and indirect thermodynamic method. Both results show good consistency, where the direct one more accurately depicts ECE value and its evolution according to phase diagram. Due to the diffuse orthorhombic-tetragonal phase transition, the samples show a broad ECE peak which shifts to lower temperature with increasing LiTaO3 amount. Compared to previous direct results in lead-free ceramics at corresponding temperatures, they show a competitive ECE performance with ΔTmax of 0.41 K (@80 °C), 0.30 K (@35 °C) and 0.16 K (@15 °C) under 20 kV/cm fields for x = 0.02, 0.0375 and 0.045.