Combined effect of grain size and tensile stresses on the ferroelectric properties of sol-gel (Pb,La)TiO3 thin films

1999 ◽  
Vol 14 (12) ◽  
pp. 4570-4580 ◽  
Author(s):  
M. Alguerá ◽  
M. L. Calzada ◽  
L. Pardo ◽  
E. Snoeck
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Size ◽  
Lead Titanate ◽  
Ferroelectric Properties ◽  
Sol Gel ◽  
Precursor Solution ◽  
Grain Size Effect ◽  
Transmission Electron ◽  
Switchable Polarization

Transmission electron microscopy has shown that the grain size of sol-gel-prepared lanthanum-modified lead titanate films increases from ∼100 to ∼1 μm when the excess of PbO in the precursor solution is reduced from 20 to 10 mol%. Switchable polarization is higher in the films with a smaller grain size. Profilometry and the temperature dependence of the dielectric permittivity indicate that films are tensile stressed by the substrate. The grain-size effect on polarization switching is explainedby taking into account this tensile stress, which is thought to induce some a-domain orientation and 90° domain wall clamping in the grains attached to the substrate.

scholarly journals The Domain and Microstructure of Resin-Bonded Magnets

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2849
Author(s):  
Marcin Jan Dośpiał
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Size ◽  
Size Distribution ◽  
Domain Structure ◽  
Grain Size Distribution ◽  
Exchange Interactions ◽  
Force Microscopy ◽  
Transmission Electron ◽  
Scanning Electron

This paper presents domain and structure studies of bonded magnets made from nanocrystalline Nd-(Fe, Co)-B powder. The structure studies were investigated using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Mössbauer spectroscopy and X-ray diffractometry. On the basis of performed qualitative and quantitative phase composition studies, it was found that investigated alloy was mainly composed of Nd2(Fe-Co)14B hard magnetic phase (98 vol%) and a small amount of Nd1.1Fe4B4 paramagnetic phase (2 vol%). The best fit of grain size distribution was achieved for the lognormal function. The mean grain size determined from transmission electron microscopy (TEM) images on the basis of grain size distribution and diffraction pattern using the Bragg equation was about ≈130 nm. HRTEM images showed that over-stoichiometric Nd was mainly distributed on the grain boundaries as a thin amorphous border of 2 nm in width. The domain structure was investigated using a scanning electron microscope and metallographic light microscope, respectively, by Bitter and Kerr methods, and by magnetic force microscopy. Domain structure studies revealed that the observed domain structure had a labyrinth shape, which is typically observed in magnets, where strong exchange interactions between grains are present. The analysis of the domain structure in different states of magnetization revealed the dynamics of the reversal magnetization process.

Interfacial precipitation in titania-doped diphasic mullite gels

1998 ◽  
Vol 13 (4) ◽  
pp. 974-978 ◽  
Author(s):  
Seong-Hyeon Hong ◽  
Naesung Lee ◽  
Altaf H. Carim ◽  
Gary L. Messing
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Phase Transformations ◽  
Orientation Relationship ◽  
Sol Gel ◽  
Sintered Body ◽  
Transmission Electron

Interfacial precipitation in sol-gel derived, titania-doped diphasic mullite gels was investigated using conventional and high resolution transmission electron microscopy. Rutile, anatase, and brookite precipitated on the interface between {110} planes of mullite and glass pockets in the sintered body. The formation of brookite may be attributable to the Si- and Al-rich environment during precipitation. Each polymorph of titania has a unique morphology and orientation relationship with mullite. Brookite exhibits a truncated pill box shape, and anatase displays a vermicular morphology. Quenching experiments suggest that the precipitates grow and undergo phase transformations during cooling.

Eu3+/Tb3+ Co-Doped Cerium Oxide Transparent Nanocomposite for Color-Tunable Emission

NANO ◽  
2018 ◽  
Vol 13 (10) ◽  
pp. 1850119
Author(s):  
Xiaoyan Li ◽  
Yunlong Yu ◽  
Xiangfeng Guan ◽  
Peihui Luo ◽  
Linqin Jiang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thermal Stability ◽  
Transmission Electron Microscopy ◽  
Sol Gel ◽  
Homogeneous Precipitation ◽  
Transmission Electron ◽  
Color Tunable ◽  
Co Doped ◽  
Tunable Emission

Eu[Formula: see text]/Tb[Formula: see text] co-doped nanocomposite containing CeO2 nanocrystals was successfully prepared by an in situ sol–gel polymerization approach. High-resolution transmission electron microscopy demonstrated the homogeneous precipitation of CeO2 nanocrystals among the polymethylmethacrylate (PMMA) matrix. The thermal stability and UV-shielding capability of the obtained nanocomposite were improved with increase of CeO2 content. The tuning of the emissive color from green and yellow to red can be easily achieved by varying the dopant species and concentration. These results suggested that the obtained nanocomposite could be potentially applicable in transparent solid-state luminescent devices.

Preparation of Titanium Oxide Nanotube by Hydrothermal Process

2007 ◽  
Vol 124-126 ◽  
pp. 1165-1168 ◽  
Author(s):  
M. Qamar ◽  
Cho Rong Yoon ◽  
Hyo Jin Oh ◽  
Anna Czoska ◽  
K. Park ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Titanium Oxide ◽  
Sol Gel ◽  
Hydrothermal Process ◽  
Hollow Fibers ◽  
Systematic Analysis ◽  
Transmission Electron ◽  
Tio2 Sol ◽  
Naoh Solution

The TiO2 sol was prepared hydrothermally in an autoclave from aqueous TiOCl2 solutions as starting precursor. Hollow fibers were obtained when sol-gel derived TiO2 sol was treated chemically with NaOH solution and subsequently heated in autoclave under various conditions. A systematic analysis of the influence of different NaOH concentrations on the formation of nanotubes has been carried out using XRD and SEM. The phase structure of the synthesized material was determined by transmission electron microscopy and found that these materials are, infact, hollow fibers widely known as nanotubes. From the TEM images, the outer and inner diameters of the tubes were measured ca. 8 and about 4 nm, respectively, with several hundred nanometers in length.

Tem Study of Yielding in Polycrystalline Gold Thin Films

1997 ◽  
Vol 505 ◽  
Author(s):  
Kwame Owusu-Boahen ◽  
Alexander H. King
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Size ◽  
Rock Salt ◽  
Gold Films ◽  
Plastic Yielding ◽  
Transmission Electron ◽  
Mean Grain Size ◽  
Polycrystalline Gold ◽  
Individual Grains

ABSTRACTWe have used transmission electron microscopy (TEM) to study the microstructure of thin gold films which were grown on 〈100〉 rock salt. The samples were annealed on the rock salt substrate or on a gold TEM specimen grid. Films annealed on rock salt had a larger mean grain size than those annealed on TEM grids. All of the annealed films have a 〈111〉 preferred orientation. Several cracks are observed in the film annealed on rock salt. Plastic yielding of the film was identified by the presence of dislocations, and is caused by tensile stress derived from grain growth. In spite of the uniform texture of the films, the observed dislocations were concentrated only in some individual grains, while their surrounding grains remained dislocation-free. Yielded grains showed no difference of orientation that would lead to higher Schmid factors, so other predictors of yielding must be considered.

The effect of grain size on microstructure and stress relaxation in polycrystalline Y1Ba2Cu3O7−δ

1989 ◽  
Vol 4 (2) ◽  
pp. 248-256 ◽  
Author(s):  
T. M. Shaw ◽  
S. L. Shinde ◽  
D. Dimos ◽  
R. F. Cook ◽  
P. R. Duncombe ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
Grain Size ◽  
Stress Relaxation ◽  
Optical Microscopy ◽  
Slow Cooling ◽  
Hierarchical Arrangement ◽  
Transmission Electron ◽  
Processing Variables

We have used transmission electron microscopy and optical microscopy to examine the effect that grain size and heat treatment have on twinning and microcracking in polycrystalline Y1Ba2Cu3O7−δ. It is shown that isothermal oxygenation heat treatments produce twin structures consisting of parallel twins, with a characteristic spacing that increases with increasing grain size. Slow cooling through the temperature range where the orthorhombic-to-tetragonal transformation induces twinning, however, produces a structure consisting of a hierarchical arrangement of intersecting twins, the scale of which appears to be independent of grain size. It is also shown that the microcracking induced by anisotropic changes in grain dimensions on cooling or during oxygenation can be suppressed if the grain size of the material is kept below about 1 μm. The results are examined in the light of current models for transformation twinning and microcracking and the models used to access the effect other processing variables such as oxygen content, doping or heat treatment may have on the microstructure of Y1Ba2Cu3O7−δ.

TEM Study of FePt and FePt:C/FePt Composite Double-Layered Thin Films

2013 ◽  
Vol 275-277 ◽  
pp. 1952-1955
Author(s):  
Ling Fang Jin ◽  
Xing Zhong Li
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Grain Size ◽  
Magnetic Properties ◽  
Composite Layer ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

New functional nanocomposite FePt:C thin films with FePt underlayers were synthesized by noneptaxial growth. The effect of the FePt layer on the ordering, orientation and magnetic properties of the composite layer has been investigated by adjusting FePt underlayer thickness from 2 nm to 14 nm. Transmission electron microscopy (TEM), together with x-ray diffraction (XRD), has been used to check the growth of the double-layered films and to study the microstructure, including the grain size, shape, orientation and distribution. XRD scans reveal that the orientation of the films was dependent on FePt underlayer thickness. In this paper, the TEM studies of both single-layered nonepitaxially grown FePt and FePt:C composite L10 phase and double-layered deposition FePt:C/FePt are presented.

TiO2-Al2O3 nanocomposites

1995 ◽  
Vol 10 (5) ◽  
pp. 1264-1269 ◽  
Author(s):  
G. Pacheco-Malagon ◽  
A. Garcia-Borquez ◽  
D. Coster ◽  
A. Sklyarov ◽  
S. Petit ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Critical Radius ◽  
Sol Gel ◽  
Atomic Ratio ◽  
Mas Nmr ◽  
Band Edge ◽  
Alumina Matrix ◽  
Transmission Electron

Nanosized TiO2 is synthesized in a nanosized alumina matrix by a sol-gel procedure. The results of the study of the blueshift of the TiO2 UV band edge are compared to the information obtained from transmission electron microscopy (TEM). As long as the atomic ratio Ti/Al remains smaller than 17.5%, no individualized TiO2 particles are detected by TEM, in spite of the fact that no modification of the alumina structure occurs, as revealed by 27Al MAS NMR. The shift of the UV band edge suggests the growth of homogeneous TiO2 domains in the alumina matrix. Above a critical radius, on the order of 1.2 nm, individual and crystalline TiO2 particles become visible in the TEM picture, and the porosity of the material decreases markedly.

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