Antiferroelectric to Paraelectric Phase Transition in Lead Zirconate Thin Films

1998 ◽  
Vol 541 ◽  
Author(s):  
D.M. Fanning ◽  
I.K. Robinson ◽  
T. Tani ◽  
D. A. Payne
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Room Temperature ◽  
Sol Gel ◽  
Lead Zirconate ◽  
First Order Phase Transition ◽  
Columnar Grains ◽  
Superstructure Peak ◽  
Paraelectric State ◽  
First Order Phase

AbstractLead zirconate, PbZrO3, is antiferroelectric at room temperature and has a first-order phase transition to the paraelectric state at 230°C in bulk crystals. At room temperature, the antiferroelectric Pb displacements along [110] directions produce a superstructure at the (h+¼ k+¼, 1) positions (referenced to pseudo-tetragonal unit cell). The Pb displacements occur perpendicular to the shorter c axis. In this study, the behavior of thin films was compared to the bulk. Films of lead zirconate were deposited onto electroded silicon wafers via the sol gel method. By varying the deposition conditions of the Pt substrate, films with both {111} and {100} preferred orientation were grown. The crystalline film consisted of columnar grains which were not completely aligned with each other, but had a random orientation with respect to the film's perpendicular axis. Measurements of superstructure peak intensities vs. temperature show that the thin films exhibit a much more gradual phase transition to the paraelectric state compared to the bulk. Furthermore, comparison of a and c vs. temperature show this effect, as well as a strain of about 0.5% in c. In the {100} oriented films, we found that the c-axis was oriented perpendicular to the film's surface, meaning they should be classified as (001).

scholarly journals 127I NQR and Crystal Structure Studies of [N(CH3)4]2 CdI4

2000 ◽  
Vol 55 (1-2) ◽  
pp. 225-229 ◽  
Author(s):  
Hideta Ishihara ◽  
Keizo Horiuchi ◽  
Thorsten M. Gesing ◽  
Shi-qi Dou ◽  
J.-Christian Buhl ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Order Phase Transition ◽  
Intensity Ratio ◽  
Room Temperature ◽  
Liquid Nitrogen Temperature ◽  
Temperature Phase ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase

The temperature dependence of 127I NQR and DSC as well as the crystal structure at room temperature of the title compound were determined. This compound shows a first-order phase transition of an order-disorder type at 245 K. Eight 127I(v1:m = ±1/2 ↔ ±3/2) NQR lines of 79.57, 81.86, 82.56, 83.36, 84.68, 87.72, 88.34, and 88.86 MHz, and corresponding eight 127I(v2: m = ±3/2 ↔±5/2) NQR lines were observed at liquid nitrogen temperature. Three 127I(υi) NQR lines wfth an intensity ratio of 1:1:2 in the order of decreasing frequency were observed just above the transition point and two NQR lines except for the middle-frequency line disappeared around room temperature. This temperature behavior of NQR lines is very similar to that observed in [N(CH3)4]2Hgl4. Another first-order phase transition takes place at 527 K. The structure of the room-temperature phase was redetermined: orthorhombic, Pnma, Z = 4, a = 1342.8(3), b = 975.7(2), c = 1696.5(3) pm. The NQR result of three lines with an intensity ratio of 1:1:2 is in agreement with this structure. The thermal displacement parameters of atoms in both cations and anions are large.

scholarly journals N-Methylpyrrolidinium hydrogen tartrate (NMPHT): an above-room-temperature order–disorder molecular switchable dielectric material

RSC Advances ◽  
2017 ◽  
Vol 7 (39) ◽  
pp. 24368-24373 ◽  
Author(s):  
Aurang Zeb ◽  
Tariq Khan ◽  
Muhammad Adnan Asghar ◽  
Zhihua Sun ◽  
Zhenyue Wu ◽  
...  
Keyword(s):  
Phase Transition ◽  
Order Phase Transition ◽  
Room Temperature ◽  
Dielectric Material ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase

A new above-room-temperature molecular switchable dielectric material, which undergoes a first-order phase transition induced by the order-disorder transformation of cation, has been reported.

Room-Temperature First-Order Phase Transition in a Charge-Disproportionated Molecular Conductor (MeEDO-TTF)2PF6

2008 ◽  
Vol 20 (24) ◽  
pp. 7551-7562 ◽  
Author(s):  
Xiangfeng Shao ◽  
Yoshiaki Nakano ◽  
Masafumi Sakata ◽  
Hideki Yamochi ◽  
Yukihiro Yoshida ◽  
...  
Keyword(s):  
Phase Transition ◽  
Order Phase Transition ◽  
Room Temperature ◽  
First Order ◽  
Molecular Conductor ◽  
First Order Phase Transition ◽  
A Charge ◽  
First Order Phase

Investigations of PbxSr1-xTiO3 Thin Films and Ceramics for Microelectronic Applications

2004 ◽  
Vol 811 ◽  
Author(s):  
M. Jain ◽  
Yu.I. Yuzyuk ◽  
R.S. Katiyar ◽  
Y. Somiya ◽  
A.S. Bhalla ◽  
...  
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Room Temperature ◽  
Sol Gel ◽  
Solid State Reaction Method ◽  
Phase Shifters ◽  
Conventional Solid State Reaction ◽  
Mode Behavior ◽  
Dielectric Devices ◽  
Pst System

ABSTRACTWe have investigated electrical and optical properties of the lead strontium titanate {(PbxSr1-x)TiO3 or PST} ceramic and dielectric properties of the thin films of PST at low and high frequencies. (PbxSr1-x)TiO3 compositions with × ≤ 0.4 are paraelectric at room temperature and exhibit ferroelectric phase transition below room temperature. Only one phase transition in the PST system (compared to three in BaxSr1-xTiO3) was recorded. The studies indicated that PST has potential for tunable microwave devices in the paraelectric phase. In the present studies, Pb0.3Sr0.7TiO3 (PST30) ceramic was prepared by the conventional solid-state reaction method and thin films of PST were prepared by sol-gel technique. Structural, microstructural, dielectric, and Raman measurements were performed on these samples. Sharp phase transition was observed in case of the ceramic by dielectric and Raman measurements at 283 K. Raman measurements revealed well-pronounced soft-mode behavior below the Curie temperature in PST ceramic. The thin film of PST deposited on lanthanum aluminate substrate was highly (100) oriented and showed dielectric maxima at ∼280 K, which was close to that in case of the bulk. Eight element coupled micro-strip phase shifters (CMPS) was fabricated on the PST film and tested in the frequency range of 15-17 GHz. The average figure of merit of 49 °/dB for PST30 film in the Ku band at 533 kV/cm suggests the potentiality of these films for high frequency tunable dielectric devices.

Effect of Strain on Barium Titanate Epitaxial Films

2013 ◽  
Vol 547 ◽  
pp. 139-144
Author(s):  
Lye Hock Ong ◽  
A.M. Alrub ◽  
Khian Hooi Chew
Keyword(s):  
Thin Films ◽  
Phase Transition ◽  
Free Energy ◽  
Epitaxial Films ◽  
Ferroelectric Films ◽  
Eighth Order ◽  
First Order ◽  
First Order Phase Transition ◽  
Highly Strained ◽  
First Order Phase

Landau-Ginzburg free energy expression with the normalized coefficients is used to elucidate the phase transition properties of strained ferroelectric films. In particular, we investigate the need to include higher order free energy terms for epitaxial strained BaTiO3 thin films. Our study reveals that the inclusion of eighth-order expression into the free energy is crucial in determining the phase transition of highly-strained BaTiO3 epitaxial films normally grown on thick cubic substrates. The phase transition is found to be second order but the unstrained film undergoes the first order phase transition. On the order hand, the calculation based on the usual sixth-order Landau-Ginzburg expression show that the films have no phase transition, which is contrary to the experimental observations.

scholarly journals The Effect of Fe Doping on the Magnetic and Magnetocaloric Properties of Mn5−xFexGe3

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Jeffrey Brock ◽  
Nathanael Bell-Pactat ◽  
Hong Cai ◽  
Timothy Dennison ◽  
Tucker Fox ◽  
...  
Keyword(s):  
Phase Transition ◽  
Order Phase Transition ◽  
Room Temperature ◽  
Entropy Change ◽  
Second Order ◽  
Ferromagnetic Transition ◽  
Fe Doping ◽  
First Order Phase Transition ◽  
Magnetocaloric Properties ◽  
First Order Phase

The magnetic and magnetocaloric properties of a series of minutely doped Mn5-xFexGe3 compounds that exhibit the D88-type hexagonal crystal structure at room temperature have been investigated. For all Fe concentrations, the alloys are ferromagnetic and undergo a second-order ferromagnetic-to-paramagnetic transition near room temperature. Although the small Fe doping had little effect on the ferromagnetic transition temperatures of the system, changes in the saturation magnetization and magnetic anisotropy were observed. For x≤0.15, all compounds exhibit nearly the same magnetic entropy change of ~7 J/kg K, for a field change of 50 kOe. However, the magnitude of the refrigerant capacities increased with Fe doping, with values up to 108.5 J/kg and 312 J/kg being observed for field changes of 20 kOe and 50 kOe, respectively. As second-order phase transition materials, the Mn5-xFexGe3 compounds are not subject to the various drawbacks associated with first-order phase transition materials yet exhibit favorable magnetocaloric effects.

scholarly journals Break of symmetry at the surface of IrTe2 upon phase transition measured by X-ray photoelectron diffraction

2021 ◽  
Author(s):  
Maxime Rumo ◽  
Aki Pulkkinen ◽  
KeYuan Ma ◽  
Fabian von Rohr ◽  
Matthias Muntwiler ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Room Temperature ◽  
Local Environment ◽  
Atomic Position ◽  
X Ray ◽  
Photoelectron Diffraction ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase

Abstract IrTe2 undergoes a series of charge-ordered phase transitions below room temperature that are characterized by the formation of stripes of Ir dimers of different periodicities. Full hemispherical X-ray photoelectron diffraction (XPD) experiments have been performed to investigate the atomic position changes undergone near the surface of 1T−IrTe2 in the first-order phase transition, from the (1 × 1) phase to the (5 × 1) phase. Comparison between experiment and simulation allows us to identify the consequence of the dimerization on the Ir atoms local environment. We report that XPD permits to unveil the break of symmetry of IrTe2 trigonal to a monoclonic unit cell and confirm the occurence of the (5 × 1) reconstruction within the first few layers below the surface with a staircase-like stacking of dimers.

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