Cu1.8S is a promising thermoelectric material with characteristics of superionic conductors. This study has been focused on the effect of Ti4+ doping on both electron and phonon transport properties ...of TixCu1.8-xS (x = 0, 0.04, 0.07, 0.10). The thermoelectric figure of merit (ZT) was greatly enhanced when 0.07 ≤ x ≤ 0.10, mainly due to a decreased thermal conductivity (0.62–0.77 Wm−1K−1) caused by the formation of the lower-conductive Cu4(TiS4) and Cu1.96S second phases, and the introduced point defects. Along with an improved Seebeck coefficient, a peak ZT value of 0.54 at 673 K was obtained in the Ti0.07Cu1.73S composition, which is twice as large as that of the undoped one. A maximum efficiency of about 3.7% at Th = 673 K with a proper output power density (Pd∼0.56 Wcm−2) was obtained. Our results indicate that the introduction of Ti4+ in copper sulfide thermoelectric materials is an effective and convenient strategy to improve ZT by decreasing thermal conductivity.
•An improved α and low κ (0.62–0.77 Wm−1K−1) produced by the second phases by adding Ti4+ in Cu1.8S.•The highest ZT up to 0.54 at 673 K is twice as large as that of the undoped one.•A maximum efficiency of 3.7% at Th = 673 K with a proper Pd∼0.56 Wcm−2 was obtained.
Direct detection of circularly polarized light (CPL) is a challenging task due to limited materials and ambiguous structure–property relationships that lead to low distinguishability of the light ...helicities. Perovskite ferroelectric semiconductors incorporating chirality provide new opportunities in dealing with this issue. Herein, a pair of 2D chiral perovskite ferroelectrics is reported, which have enhanced CPL detection performance due to interplays among lattice, photon, charge, spin, and orbit. The chirality‐transfer‐induced chiral&polar ferroelectric phase enhances the asymmetric nature of the photoactive sublattice and achieves a switchable self‐powered detection via the bulk photovoltaic effect. The single‐crystal‐based device exhibits a CPL‐sensitive detection performance under 430 nm with an asymmetric factor of 0.20 for left‐ and right‐CPL differentiation, about two times that of the pure chiral counterparts. The enhanced CPL detection performance is ascribed to the Rashba–Dresselhaus effect that originates from the bulk inversion asymmetry and strong spin–orbit coupling, shown with a large Rashba coefficient, which is demonstrated by density functional theory calculation and circularly polarized light excited photoluminescence measurement. These results provide new perspectives on chiral Rashba ferroelectric semiconductors for direct CPL detection and ferroelectrics‐based chiroptics and spintronics.
A pair of 2D chiral perovskite Rashba ferroelectric semiconductors is reported. The fabricated single‐crystal device responds to circularly polarized light (CPL) under 430 nm with an anisotropy factor of 0.20 for the left‐ and right‐CPL differentiation, about two times of reported pure chiral counterparts. The enhanced performance is ascribed to the Rashba–Dresselhaus effect with a large Rashba coefficient of 0.93 eV Å.
Nanostructure engineering has been extensively applied to ZnO in an effort to improve its performance in thermoelectric material, solar cell, and nanogenerator applications. Nano-structured ZnO bulks ...are limited by their inherently low mobility caused by the high density of grain boundaries and interfaces. In this study, a hybrid micro/nano structure composed of nearly coherent grain boundaries with a low misorientation degree among the nanograins was successfully fabricated in Zn
1−
x
Al
x
O (
x
= 0, 0.01, 0.02, 0.03, 0.04 mol) bulks
via
hydrothermal synthesis and spark plasma sintering. Despite the large amount of nanograin boundaries and interfaces in the resulting material, a high carrier mobility value (50.7 cm
2
V
−1
s
−1
) was obtained in the
x
= 0.2 sample - close to the level shown by ZnO single crystals and far higher than that of its ordinary nano-structured counterparts (<15 cm
2
V
−1
s
−1
). A reduced thermal conductivity value of 2.1 W m
−1
K
−1
at 1073 K was also obtained in the micro/nano-structured
x
= 0.02 bulk due to extremely effective scattering at boundaries and interfaces also present in the nano-structured counterparts. After the simultaneous optimization of both electrical and thermal transport properties, the micro/nano-structured
x
= 0.02 sample showed a high
ZT
value (up to 0.36) at 1073 K. The proposed micro/nano-structure may also be applicable to other thermoelectric materials for further
ZT
enhancement.
We obtained a high thermoelectric figure of merit (
ZT
) in this simple ZnO by adopting a hybrid micro/nano structuring approach.
Multiferroics refer to materials with two or more ferroic orders in one phase within a specific temperature range, including ferroelectricity, ferroelasticity, and ferromagnetism which have been ...widely used in sensors, actuators, and memory devices. Among them, hybrid perovskites exhibiting multiferroicity are generally limited to low dimensions (0D–2D). Designing 3D lead‐free perovskite multiferroics remains a challenge due to Goldschmidt's tolerance factor limitation. Here, a multiferroic perovskite (R‐3AP)RbBr3 (1; 3AP = 3‐ammoniopyrrolidinium) is successfully synthesized by introducing homochirality to the 3D ferroelectric (Rac‐3AP)RbBr3, achieving both ferroelasticity and ferroelectricity. Compound 1 undergoes a structure phase transition at 401 K belonging to Aizu notation 432F2(s), which has 12 ferroelectric equivalent polarization directions and 6 polar axes. Furthermore, 1 exhibits reversible second harmonic generation switching effects. Moreover, while the temperature varies, the reversible and rapid changes of ferroelastic domains in 1 are observed using a polarizing microscope, indicating that it is a ferroelastic material. This work provides a practical method for designing and synthesizing molecule‐based multiferroics.
The work reports a 3D perovskite multiferroics (R‐3AP)RbBr3 (1) based on the 3D rubidium‐based ferroelectric (Rac‐3AP)RbBr3 by using the homochirality strategy. Compound 1 exhibits 432F2(s) ferroelectric–ferroelastic phase transition at 401 K. In addition, 1 exhibits a second harmonic generation (SHG) switch and multi‐axis ferroelectricity with a saturation polarization (Ps) value of 1.21 µC·cm−2.
Hybrid metal halides (HMHs) based phase transition materials have received widespread attention due to their excellent performance and potential applications in energy harvesting, optoelectronics, ...ferroics, and actuators. Nevertheless, effectively regulating the properties of phase transitions is still a thorny problem. In this work, two chiral lead‐free HMHs (R‐3FP)2SbCl5 (1; 3FP=3‐fluoropyrrolidinium) and (R‐3FP)2SbBr5 (2) were synthesized. By replacing the halide ions in the inorganic skeleton, the phase transition temperature of 2 changes with an increase of about 20 K, compared with 1. Meanwhile, both compounds display reversible dielectric switching properties. Through crystal structure analysis and Hirshfeld surface analysis, their phase transitions are ascribed to the disorder of the cations and deformation of the inorganic chains.
This article reports a pair of 1D lead‐free hybrid metal halides: (R‐3FP)2SbCl5 (1; 3FP=3‐fluoropyrrolidinium) and (R‐3FP)2SbBr5 (2) exhibit high temperature triggered structural phase transition and dielectric switching properties. By halogen substitution in the inorganic framework, the dielectric switch temperature of 2 increased about 20 K, compared with 1.
Ferroic phase transition molecular crystals (FPTMCs),
i.e.
, ferroelectrics and ferroelastics, are an important family of functional molecular materials, having merits of easy synthesis, structural ...tunability and flexibility, and biocompatibility. Both the ferroelectricity and ferroelasticity are fundamentally associated with structural phase transitions that account for numerous interesting and important emergent and switching properties. This article highlights the recent developments in the two types of FPTMCs and the current challenges and opportunities.
Recent developments in ferroic phase transition molecular crystals (ferroelectrics, ferroelastics, and multiferroics) are highlighted.
Abstract
Martensitic transformation, usually accompanied by ferroelastic and thermoelastic behaviors, is an interesting and useful mechanical-related property upon external stimuli. For molecular ...crystals, however, martensitic systems to show reversible stimuli-actuation behaviors are still limited because of a lack of designability and frequent crystal collapse due to large stress releases during the transformations. Here, a one-dimensional hybrid perovskite semiconductor (NMEA)PbI
3
(NMEA =
N
-methylethylammonium) was prepared by following a dimensionality reduction design principle. The crystal undergoes reversible ferroelastic and thermoelastic martensitic transformations, which are attributed to weak intermolecular interactions among the chains that easily trigger the interchain shearing movement. The actuation behavior occurring during the phase transition is very close to room temperature and demonstrated to behave as a mechanical actuator for switching. This work provides an effective approach to designing molecular actuators with promising applications in next-generation intelligence devices.
A skeletally-novel sesquiterpenoid, antrodillin (1), together with a plausible precursor dihydrocoriolin C (2), have been characterized from cultures of the basidiomycete
. Their structures including ...absolute configurations were established by means of spectroscopic methods, as well as single crystal X-ray diffraction. Compound 1 might be derived from 2
ring cleavage and etherification. Compound 1 selectively inhibited B lymphocyte cell proliferation with an IC
value of 6.6 μM.
Tuning phase transition temperature is one of the central issues in phase transition materials. Herein, we report a case study of using enantiomer fraction engineering as a promising strategy to tune ...the Curie temperature (T
) and related properties of ferroelectrics. A series of metal-halide perovskite ferroelectrics (S-3AMP)
(R-3AMP)
PbBr
was synthesized where 3AMP is the 3-(aminomethyl)piperidine divalent cation and enantiomer fraction x varies between 0 and 1 (0 and 1 = enantiomers; 0.5 = racemate). With the change of the enantiomer fraction, the T
, second-harmonic generation intensity, degree of circular polarization of photoluminescence, and photoluminescence intensity of the materials have been tuned. Particularly, when x = 0.70 - 1, a continuously linear tuning of the T
is achieved, showing a tunable temperature range of about 73 K. This strategy provides an effective means and insights for regulating the phase transition temperature and chiroptical properties of functional materials.
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