On the tetragonality of the room-temperature ferroelectric phase of barium titanate, BaTiO3

2009 ◽  
Vol 42 (3) ◽  
pp. 480-484 ◽  
Author(s):  
Dean S. Keeble ◽  
Pamela A. Thomas
Keyword(s):  
Barium Titanate ◽  
Diffraction Pattern ◽  
Room Temperature ◽  
Ferroelectric Material ◽  
Tetragonal Symmetry ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Group Assignment ◽  
Growth Method

The room-temperature phase of the important ferroelectric material barium titanate, BaTiO3, was re-investigated by single-crystal X-ray diffraction on a sample grown by the top-seeded solution growth method, with the intention of demonstrating once again that the structure has tetragonal symmetry consistent with the space-group assignmentP4mmand thus resolving recent controversy in the scientific community and literature [Yoshimura, Kojima, Tokunaga, Tozaki & Koganezawa (2006).Phys. Lett. A,353, 250–254; Yoshimura, Morioka, Kojima, Tokunaga, Koganezawa & Tozaki (2007).Phys. Lett. A,367, 394–401]. To this end, the X-ray diffraction pattern of a small (341 µm3) sample of top-seeded solution-grown BaTiO3was measured using an Oxford Diffraction Gemini CCD diffractometer employing Mo Kα radiation and an extended 120 mm sample-to-detector distance. More than 104individual diffraction maxima observed out to a maximum resolution of 0.4 Å were indexed on two tetragonal lattices. These were identical to within the standard deviations on the lattice parameters and were related to each other by a single rotation of 119.7° about the [11\overline1] direction of the first tetragonal lattice (the major twin component), although the actual twinning operation that explains the observed diffraction pattern both qualitatively and quantitatively is shown to be conventional 90° twinning by them[101] operation. Importantly, it is not necessary to invoke either monoclinic symmetry or a coexistence of tetragonal and monoclinic phases to explain the observed diffraction data.

Electron Microscope study of commensurate-incommensurate phase transition in BaZnGeO4

1990 ◽  
Vol 48 (4) ◽  
pp. 172-173
Author(s):  
Naoki Yamamoto ◽  
Makoto Kikuchi ◽  
Tooru Atake ◽  
Akihiro Hamano ◽  
Yasutoshi Saito
Keyword(s):  
Phase Transition ◽  
Electron Microscope Study ◽  
Room Temperature ◽  
Hexagonal Lattice ◽  
Ferroelectric Materials ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Periodic Arrays ◽  
Modulation Wave Vector

BaZnGeO4 undergoes many phase transitions from I to V phase. The highest temperature phase I has a BaAl2O4 type structure with a hexagonal lattice. Recent X-ray diffraction study showed that the incommensurate (IC) lattice modulation appears along the c axis in the III and IV phases with a period of about 4c, and a commensurate (C) phase with a modulated period of 4c exists between the III and IV phases in the narrow temperature region (—58°C to —47°C on cooling), called the III' phase. The modulations in the IC phases are considered displacive type, but the detailed structures have not been studied. It is also not clear whether the modulation changes into periodic arrays of discommensurations (DC’s) near the III-III' and IV-V phase transition temperature as found in the ferroelectric materials such as Rb2ZnCl4.At room temperature (III phase) satellite reflections were seen around the fundamental reflections in a diffraction pattern (Fig.1) and they aligned along a certain direction deviated from the c* direction, which indicates that the modulation wave vector q tilts from the c* axis. The tilt angle is about 2 degree at room temperature and depends on temperature.

The structures and phase transitions in 4-aminopyridinium tetraaquabis(sulfato)iron(III), (C5H7N2)[FeIII(H2O)4(SO4)2]

2019 ◽  
Vol 75 (6) ◽  
pp. 1144-1151
Author(s):  
Tamara J. Bednarchuk ◽  
Wolfgang Hornfeck ◽  
Vasyl Kinzhybalo ◽  
Zhengyang Zhou ◽  
Michal Dušek ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Single Crystal ◽  
Room Temperature ◽  
Variable Temperature ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Hybrid Compound ◽  
Space Group ◽  
X Ray

The organic–inorganic hybrid compound 4-aminopyridinium tetraaquabis(sulfato)iron(III), (C5H7N2)[FeIII(H2O)4(SO4)2] (4apFeS), was obtained by slow evaporation of the solvent at room temperature and characterized by single-crystal X-ray diffraction in the temperature range from 290 to 80 K. Differential scanning calorimetry revealed that the title compound undergoes a sequence of three reversible phase transitions, which has been verified by variable-temperature X-ray diffraction analysis during cooling–heating cycles over the temperature ranges 290–100–290 K. In the room-temperature phase (I), space group C2/c, oxygen atoms from the closest Fe-atom environment (octahedral) were disordered over two equivalent positions around a twofold axis. Two intermediate phases (II), (III) were solved and refined as incommensurately modulated structures, employing the superspace formalism applied to single-crystal X-ray diffraction data. Both structures can be described in the (3+1)-dimensional monoclinic X2/c(α,0,γ)0s superspace group (where X is ½, ½, 0, ½) with modulation wavevectors q = (0.2943, 0, 0.5640) and q = (0.3366, 0, 0.5544) for phases (II) and (III), respectively. The completely ordered low-temperature phase (IV) was refined with the twinning model in the triclinic P{\overline 1} space group, revealing the existence of two domains. The dynamics of the disordered anionic substructure in the 4apFeS crystal seems to play an essential role in the phase transition mechanisms. The discrete organic moieties were found to be fully ordered even at room temperature.

Differences and similarities among hypoxanthinium nitrate hydrate structures

2019 ◽  
Vol 75 (8) ◽  
pp. 1036-1044 ◽  
Author(s):  
Małgorzata Katarzyna Cabaj ◽  
Roman Gajda ◽  
Anna Hoser ◽  
Anna Makal ◽  
Paulina Maria Dominiak
Keyword(s):  
Room Temperature ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Acta Cryst ◽  
X Ray ◽  
Nitrate Hydrate ◽  
Different Temperatures ◽  
Lower Temperature ◽  
Low Temperature Phase ◽  
Nitrate Anions

Crystals of hypoxanthinium (6-oxo-1H,7H-purin-9-ium) nitrate hydrates were investigated by means of X-ray diffraction at different temperatures. The data for hypoxanthinium nitrate monohydrate (C5H5N4O+·NO3 −·H2O, Hx1) were collected at 20, 105 and 285 K. The room-temperature phase was reported previously [Schmalle et al. (1990). Acta Cryst. C46, 340–342] and the low-temperature phase has not been investigated yet. The structure underwent a phase transition, which resulted in a change of space group from Pmnb to P21/n at lower temperature and subsequently in nonmerohedral twinning. The structure of hypoxanthinium dinitrate trihydrate (H3O+·C5H5N4O+·2NO3 −·2H2O, Hx2) was determined at 20 and 100 K, and also has not been reported previously. The Hx2 structure consists of two types of layers: the `hypoxanthinium nitrate monohydrate' layers (HX) observed in Hx1 and layers of Zundel complex H3O+·H2O interacting with nitrate anions (OX). The crystal can be considered as a solid solution of two salts, i.e. hypoxanthinium nitrate monohydrate, C5H5N4O+·NO3 −·H2O, and oxonium nitrate monohydrate, H3O+(H2O)·NO3 −.

scholarly journals Structural and Optical Studies of Potential Ferroelectric Crystal: KDP Doped TGS

2013 ◽  
Vol 6 (1) ◽  
pp. 1-9 ◽  
Author(s):  
P. R. Deepti ◽  
J. Shanti
Keyword(s):  
Infrared Detectors ◽  
Room Temperature ◽  
Grown Crystal ◽  
High Sensitivity ◽  
Ferroelectric Material ◽  
X Ray Diffraction ◽  
Optical Studies ◽  
Ferroelectric Crystal ◽  
X Ray ◽  
Vis Spectroscopy

Triglycine sulphate (TGS), an important ferroelectric material has been widely used in the fabrication of high sensitivity infrared detectors at room temperature. Single crystals of KDP doped TGS was grown by slow evaporation method at room temperature in this study. The grown crystal was characterized by UV-Vis spectroscopy, FTIR spectroscopy, powder X-ray diffraction studies, and ferroelectric studies. KDP doped TGS crystals were found to be highly transparent and full faced. The experimental results evidence the suitability of the grown crystal for optoelectronic applications.  Keywords: Crystal growth; KDP-doped TGS; Ferroelectric studies  © 2014 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.  doi: http://dx.doi.org/10.3329/jsr.v6i1.16584 J. Sci. Res. 6 (1), 1-9 (2014)

scholarly journals Получение, структура, диэлектрические и магнитные свойства керамики SrFe-=SUB=-2/3-=/SUB=-W-=SUB=-1/3-=/SUB=-O-=SUB=-3-=/SUB=-

2018 ◽  
Vol 60 (3) ◽  
pp. 510
Author(s):  
А.В. Павленко ◽  
А.В. Турик ◽  
Л.А. Шилкина ◽  
С.П. Кубрин ◽  
Ю.B. Русалев ◽  
...  
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Solid Phase ◽  
Ceramic Technology ◽  
Tetragonal Symmetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Solid Phase Reactions ◽  
Perovskite Type ◽  
Perovskite Type Structure

AbstractPolycrystalline samples of SrFe_2/3W_1/3O_3 (SFWO) ceramic were obtained by solid-phase reactions with subsequent sintering using conventional ceramic technology. X-ray diffraction analysis showed that at room temperature, the SFWO ceramic is single-phase and has a perovskite-type structure with tetragonal symmetry and parameters a = 3.941(9) Å, c = 3.955(6) Å, and c/a = 1.0035. In studying the magnetic properties and the Mössbauer effect in SFWO ceramics, it is found that the material is a ferrimagnet, and the iron ions are only in the valence state of Fe^3+. It is suggested that in the temperature range of T = 150–210°C, a smeared phase transition from a cubic (paraelectric) phase to a tetragonal (ferroelectric) phase takes place in SFWO with decreasing temperature.

scholarly journals Comment on ‘Multilayered Stable 2D Nano-Sheets of Ti2NTx MXene: Synthesis, Characterization, and Anticancer Activity’

2020 ◽  
Author(s):  
Yitong Guo ◽  
Qianku Hu ◽  
Libo Wang ◽  
Aiguo Zhou
Keyword(s):  
Anticancer Activity ◽  
Diffraction Pattern ◽  
Hydrofluoric Acid ◽  
Recent Article ◽  
Room Temperature ◽  
Max Phase ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray

<p>A recent article entitled “Multilayered stable 2D nano-sheets of Ti<sub>2</sub>NT<sub>x</sub> MXene: synthesis, characterization, and anticancer activity” published in this journal, claimed that two-dimensional Ti<sub>2</sub>NT<sub>x</sub> MXene could be synthesized by selectively etching Ti<sub>2</sub>AlN in concentrated hydrofluoric acid at room temperature. However, the X-ray diffraction pattern of Ti<sub>2</sub>NT<sub>x</sub> MXene reported in that paper is completely different with those of other MXenes. In this comment, it is argued that the samples synthesized in that paper were NOT Ti<sub>2</sub>NT<sub>x</sub> MXene at all. Although carbide MXenes can be made by selectively etching A layers from MAX phase, it is very difficult or impossible to make nitride MXenes (Ti<sub>2</sub>NT<sub>x</sub>) by the same way.</p>

Structural, Morphological and Thermal Decomposition Studies of Calcium and Hafnium Modified BaTiO3 Electro Ceramics

2021 ◽  
Author(s):  
Jude Fernandez ◽  
B Bindhu ◽  
M. Prabu ◽  
KY Sandhya
Keyword(s):  
Lead Zirconate Titanate ◽  
Sol Gel ◽  
Lead Zirconate ◽  
Ferroelectric Material ◽  
Tetragonal Symmetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gel Combustion ◽  
Combustion Technique ◽  
P4mm Space Group

Abstract Calcium and hafnium co-doped barium titanate could be used as a replacement for lead zirconate titanate, which is a lead-based ferroelectric material. Solid state reaction accompanied by the usual sintering technique is the classical ceramic-processing method, which demands a lot of time and effort. The present work aims to make the process a lot easier and quicker by employing a modified sol-gel combustion technique to synthesize polycrystalline Ba0.85Ca0.15Ti(1-x)HfxO3 (x=0.00, 0.05, 0.10, 0.15) electro ceramics . The molar ration is fixed at 1:1 for metal and citric acid at pH ~ 1. It was found that Ba0.85Ca0.15Ti(1-x)HfxO3 (where x=0.00, 0.05, 0.10, 0.15) crystallizes completely at around 1000 °C which is much lower than traditional methods. The structure supposedly displays a tetragonal symmetry with the P4mm space group as confirmed through x-ray diffraction (XRD) and Raman spectroscopy.

The Origin of the Ferroelectricity in the Bismuth Titanate Bi4Ti3O12 with Perovskite-Like Layered Structure

2015 ◽  
Vol 226 ◽  
pp. 17-22 ◽  
Author(s):  
Joanna A. Bartkowska ◽  
Jolanta Dercz ◽  
Daniel Michalik
Keyword(s):  
Room Temperature ◽  
Bismuth Titanate ◽  
Diffraction Method ◽  
Ceramic Materials ◽  
Ferroelectric Material ◽  
X Ray Diffraction ◽  
Electronic Industry ◽  
X Ray ◽  
Formation Behavior ◽  
Thermogravimetric Studies

The goal of this study was to investigate the origin of ferroelectricity in Bi4Ti3O12. The bismuth titanate Bi4Ti3O12 (BTO), which belongs to the Aurivillius family, is one of the most interesting compounds among the bismuth-based layered ceramics. BTO is a ferroelectric material with wide applications in the electronic industry, as capacitors, transducers, memory devices and sensors. Aurivillius structures are described with a general formula following form:Am-1Bi2BmO3m-1. BTO ceramic materials is an Aurivillius structure with m = 3. This ceramic materials were prepared by conventional mixed-oxide method of the solid state reaction. The temperature of the Bi4Ti3O12 sintering was selected on basis of thermogravimetric studies. The crystal structure of Bi4Ti3O12 was examined at room temperature with an X-ray diffraction method. Phase formation behavior was investigated using the differential thermal analysis (DTA) and the thermal gravimetric (TG). The microstructure was investigated by SEM method. Based on the Dorrian’s model, the value of displacements between bismuth ions and oxygen octahedra was calculated.

Structure refinement of Cu8GeS6 using X-ray diffraction data from a multiple-twinned crystal

1999 ◽  
Vol 55 (5) ◽  
pp. 721-725 ◽  
Author(s):  
Mitsuko Onoda ◽  
Xue-An Chen ◽  
Katsuo Kato ◽  
Akira Sato ◽  
Hiroaki Wada
Keyword(s):  
Diffraction Data ◽  
Room Temperature ◽  
Structure Refinement ◽  
Unit Cell ◽  
Temperature Phase ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Germanium Sulfide ◽  
Symmetry Operations

The structure of the orthorhombic room-temperature phase of Cu8GeS6 (copper germanium sulfide), Mr = 773.27, has been refined on the basis of X-ray diffraction data from a 12-fold twinned crystal applying a six-dimensional twin refinement technique. For 1804 unique reflections measured using Mo Kα radiation, RF was 0.083 with 77 structure parameters and 12 scale factors. The symmetry operations, the unit cell and other crystal data are (0, 0, 0; ½, ½, 0) + x, y, z; y, x, z; ¼ − x, ¾ − y, ½ + z; ¾ − y, ¼ − x, ½ + z; a = b = 9.9073 (3) Å, c = 9.8703 (4) Å, α = β = 90°, γ = 90.642 (4)°; V = 968.7 (1) Å3, Z = 4, Dx  = 5.358 Mg m−3, μ = 21.70 mm−1. The standard setting of the space group and the reduced unit cell are Pmn21; a = 7.0445 (3), b = 6.9661 (3), c = 9.8699 (5) Å; Z = 2.

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