Ferroelectrics and the Curie-Weiss law

Trainer, Matthew

doi:10.1088/0143-0807/21/5/312

Cited by 48 publications

(23 citation statements)

References 19 publications

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“…Measuring real (« re ) and the imaginary (« im ) relative permittivity as a function of temperature shows a dielectric anomaly around T c (Fig. 2C), as also previously observed in polycrystalline MAPbI 3 films (30), which supports the conclusion that tetragonal MAPbI 3 is ferroelectric (14,51). The disappearance and reappearance of the pyroelectric response after exceeding the T c to the cubic phase and cooling back to the tetragonal phase, lends further support to the polar nature of tetragonal MAPbI 3 and the nonpolar nature of the cubic phase, a result that agrees with our results for MAPbBr 3 (22).…”

Section: Applied Physical Sciencessupporting

confidence: 87%

Tetragonal CH ₃ NH ₃ PbI ₃ is ferroelectric

Rakita

Bar-Elli

Meirzadeh

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

262

221

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Halide perovskite (HaP) semiconductors are revolutionizing photovoltaic (PV) solar energy conversion by showing remarkable performance of solar cells made with HaPs, especially tetragonal methylammonium lead triiodide (MAPbI 3 ). In particular, the low voltage loss of these cells implies a remarkably low recombination rate of photogenerated carriers. It was suggested that low recombination can be due to the spatial separation of electrons and holes, a possibility if MAPbI 3 is a semiconducting ferroelectric, which, however, requires clear experimental evidence. As a first step, we show that, in operando, MAPbI 3 (unlike MAPbBr 3 ) is pyroelectric, which implies it can be ferroelectric. The next step, proving it is (not) ferroelectric, is challenging, because of the material's relatively high electrical conductance (a consequence of an optical band gap suitable for PV conversion) and low stability under high applied bias voltage. This excludes normal measurements of a ferroelectric hysteresis loop, to prove ferroelectricity's hallmark switchable polarization. By adopting an approach suitable for electrically leaky materials as MAPbI 3 , we show here ferroelectric hysteresis from well-characterized single crystals at low temperature (still within the tetragonal phase, which is stable at room temperature). By chemical etching, we also can image the structural fingerprint for ferroelectricity, polar domains, periodically stacked along the polar axis of the crystal, which, as predicted by theory, scale with the overall crystal size. We also succeeded in detecting clear second harmonic generation, direct evidence for the material's noncentrosymmetry. We note that the material's ferroelectric nature, can, but need not be important in a PV cell at room temperature.halide perovskites | photovoltaics | semiconductors | ferroelectricity | pyroelectricity N ew optoelectronic materials are of interest for producing solar cells with higher power and voltage efficiencies, lower costs, and improved long-term reliability. A very recent entry is the family of halide perovskites (HaPs), in particular those based on methylammonium (MA) lead iodide (MAPbI 3 ), MAPbBr 3 , and its inorganic analog CsPbBr 3 . Devices based on these perform remarkably well as solar cells (1, 2), as well as in other optoelectronic applications, such as LEDs and electromagnetic radiation detectors (3-5). Understanding possible unique characteristics of HaPs may show the way to other materials with similar key features.The ABX 3 (X = I, Br, Cl) HaP semiconductors (SCs), that is, with perovskite or perovskite-like structures, reach, via a steep absorption edge, a high optical absorption coefficient (∼10 5 cm −1 ) (6, 7), long charge carrier lifetimes (∼0.1-1 μs) (8), and reasonable carrier mobilities (less than or equal to ∼100 cm 2 ·V −1 ·s −1 ) (9), and have a low exciton binding energy (10). With these characteristics, the thickness of the optical absorber layer can be ≤0.5 μm, which allows the charge carriers (separated electrons and holes) to diffuse/d...

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Section: Applied Physical Sciencessupporting

confidence: 87%

Tetragonal CH ₃ NH ₃ PbI ₃ is ferroelectric

Rakita

Bar-Elli

Meirzadeh

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

262

221

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“…[29][30][31] The permittivity of unstrained SrTiO 3 increases from e 0 % 300 at room temperature to e 0 % 25 000 at 4 K; however, polarization-electricfield hysteresis-a signature of ferroelectricity-does not develop even at lowest temperatures. In the dielectric regime, the temperature-dependence of the permittivity is described by the Curie-Weiss law, e 0 (T) / (TÀT c ) À1 with a Curie temperature for unstrained pure SrTiO 3 of T c % 49 K. 32 However, the quantum paraelectric state is very sensitive to small perturbations. Ferroelectricity can be induced among others by mechanical stress.…”

Section: Resultsmentioning

confidence: 99%

Relaxor ferro- and paraelectricity in anisotropically strained SrTiO3 films

Wördenweber

Schubert

Ehlig

et al. 2013

Journal of Applied Physics

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“…This results in a large degree of unstable polarization, and consequently, an applied electric field can easily produce considerable variation in polarization [24]. The decrease in the dielectric constant above T c is caused by the thermal detriment of polarization alignment [24,25]. Because BZT ceramic is classified as a ferroelectric material, the dielectric characteristic of BZT above the Curie temperature corresponds to the Curie-Weiss law: 1/ε r = (T − T 0 )/C (T > T c ), where T 0 and C are the Curie-Weiss temperature and constant, respectively.…”

Section: Resultsmentioning

confidence: 99%

Energy Conversion Capacity of Barium Zirconate Titanate

et al. 2020

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In this study, we investigated the effect of zirconium content on lead-free barium zirconate titanate (BZT) (Ba(ZrxTi1−x)O3, with x = 0.00, 0.01, 0.03, 0.05, and 0.08), which was prepared by the sol–gel method. A single-phase perovskite BZT was obtained under calcination and sintering conditions at 1100 °C and 1300 °C. Ferroelectric measurements revealed that the Curie temperature of BaTiO3 was 399 K, and the transition temperature decreased with increasing zirconium content. At the Curie temperature, Ba(Zr0.03Ti0.97)O3 with a dielectric constant of 19,600 showed the best performance in converting supplied mechanical vibration into electrical power. The experiments focused on piezoelectric activity at a low vibrating frequency, and the output power that dissipated from the BZT system at 15 Hz was 2.47 nW (30 MΩ). The prepared lead-free sol–gel BZT is promising for energy-harvesting applications considering that the normal frequencies of ambient vibration sources are less than 100 Hz.

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Ferroelectrics and the Curie-Weiss law

Cited by 48 publications

References 19 publications

Tetragonal CH ₃ NH ₃ PbI ₃ is ferroelectric

Tetragonal CH ₃ NH ₃ PbI ₃ is ferroelectric

Relaxor ferro- and paraelectricity in anisotropically strained SrTiO3 films

Energy Conversion Capacity of Barium Zirconate Titanate

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Ferroelectrics and the Curie-Weiss law

Cited by 48 publications

References 19 publications

Tetragonal CH 3 NH 3 PbI 3 is ferroelectric

Tetragonal CH 3 NH 3 PbI 3 is ferroelectric

Relaxor ferro- and paraelectricity in anisotropically strained SrTiO3 films

Energy Conversion Capacity of Barium Zirconate Titanate

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Tetragonal CH ₃ NH ₃ PbI ₃ is ferroelectric

Tetragonal CH ₃ NH ₃ PbI ₃ is ferroelectric