Investigation of grain boundaries for abnormal grain growth in polycrystalline SrTiO3

2010 ◽  
Vol 25 (2) ◽  
pp. 260-265 ◽  
Author(s):  
Shao-Ju Shih ◽  
Sergio Lozano-Perez ◽  
David J.H. Cockayne
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Energy Dispersive Spectrometry ◽  
Dominant Role ◽  
Morphological Type ◽  
Liquid Films ◽  
Model Material ◽  
Abnormal Grain Growth ◽  
Transmission Electron ◽  
Microstructural Behavior

Strontium titanate (SrTiO3) is widely used in electronic devices, and it is a model material for understanding the structural and dielectric properties of grain boundaries (GBs). In such materials, the GBs often play a dominant role in sintering and microstructural behavior. Abnormal grain growth (AGG) is a commonly observed phenomenon. Most studies explained that GBs contain continuous liquid films, and this liquid assists interface diffusion resulting in fast growth. However, few studies investigate the AGG behavior without any liquid. In this study, GB morphology and chemistry have been characterized by high-resolution transmission electron microscopy and x-ray energy-dispersive spectrometry, respectively. Different distributions of GB morphology have been observed in abnormal grains and matrix grains, and GB chemistry varies with different morphological type GBs. By correlating GB morphology and chemistry, a possible mechanism for AGG is proposed.

A Role of Low Energy Grain Boundaries in the Abnormal Grain Growth in Fe-3%Si Alloy

2011 ◽  
Vol 127 ◽  
pp. 89-94 ◽  
Author(s):  
Ye Chao Zhu ◽  
Jiong Hui Mao ◽  
Fa Tang Tan ◽  
Xue Liang Qiao
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Electron Backscatter Diffraction ◽  
Dominant Role ◽  
Coincidence Site Lattice ◽  
Diffraction Method ◽  
Abnormal Grain Growth ◽  
Low Energy ◽  
Backscatter Diffraction

Low energy grain boundaries were considered to be important in abnormal grain growth by theoretical deduction. The disorientation angles and coincidence site lattice grain boundaries distribution of more than 20 Goss grains and their neighboring matrix grains in primary recrystallized Fe-3%Si alloy were investigated using an electron backscatter diffraction method. It was found that the frequency of low energy grain boundaries of Goss grains which are more likely to abnormally grow are higher than their neighboring matrix grains, which indicated that low energy grain boundaries play a dominant role in the abnormal grain growth of Fe-3%Si alloy. The result meets well with the abnormal grain growth theory.

An Overview of Accomplishments and Challenges in Recrystallization and Grain Growth

2007 ◽  
Vol 558-559 ◽  
pp. 33-42 ◽  
Author(s):  
Anthony D. Rollett ◽  
Abhijit P. Brahme ◽  
C.G. Roberts
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Degrees Of Freedom ◽  
Driving Forces ◽  
Excess Free Energy ◽  
Abnormal Grain Growth ◽  
Process Models ◽  
Three Dimensions ◽  
Polycrystalline Materials ◽  
General Process

The study of microstructural evolution in polycrystalline materials has been active for many decades so it is interesting to illustrate the progress that has been made and to point out some remaining challenges. Grain boundaries are important because their long-range motion controls evolution in many cases. We have some understanding of the essential features of grain boundary properties over the five macroscopic degrees of freedom. Excess free energy, for example, is dominated by the two surfaces that comprise the boundary although the twist component also has a non-negligible influence. Mobility is less well defined although there are some clear trends for certain classes of materials such as fcc metals. Computer simulation has made a critical contribution by showing, for example, that mobility exhibits an intrinsic crystallographic anisotropy even in the absence of impurities. At the mesoscopic level, we now have rigorous relationships between geometry and growth rates for individual grains in three dimensions. We are in the process of validating computer models of grain growth against 3D non-destructive measurements. Quantitative modeling of recrystallization that includes texture development has been accomplished in several groups. Other properties such as corrosion resistance are being related quantitatively to microstructure. There remain, however, numerous challenges. Despite decades of study, we still do not have complete cause-and-effect descriptions of most cases of abnormal grain growth. The response of nanostructured materials to annealing can lead to either unexpected resistance to coarsening, or, coarsening at unexpectedly low temperatures. General process models for recrystallization that can be applied to industrial alloys remain elusive although significant progress has been made for the specific case of aluminum alloy processing. Thin films often exhibit stagnation of grain growth that we do not fully understand, as well as abnormal grain growth. Grain boundaries respond to driving forces in more complicated ways than we understood. Clearly many exciting challenges remain in grain growth and recrystallization.

Evolution of phases and microstructure in optical waveguides of lithium niobate

1994 ◽  
Vol 9 (8) ◽  
pp. 2040-2050 ◽  
Author(s):  
M.A. McCoy ◽  
S.A. Dregia ◽  
W.E. Lee
Keyword(s):  
Solid Solution ◽  
Lithium Niobate ◽  
Grain Growth ◽  
Optical Waveguides ◽  
Abnormal Grain Growth ◽  
Microstructural Development ◽  
X Ray Diffraction ◽  
Rutile Structure ◽  
Transmission Electron ◽  
Epitaxial Grain Growth

The microstructural development of Ti: LiNbO3 optical waveguides, as a function of annealing time and temperature, was studied by x-ray diffraction, scanning and transmission electron microscopy, and Auger electron spectroscopy. The microstructure evolves in three major stages: oxidation, precipitation and abnormal grain growth, and interdiffusion. The deposited Ti film is oxidized at low temperatures through a series of intermediate TiOx phases until complete oxidation to rutile TiO2 occurs at ∼500 °C. At intermediate temperatures, 500-800 °C, epitaxial precipitates of LiNb3O8 are formed at the rutile/LiNbO3 interface. At this stage abnormal grain growth occurs in the rutile film, causing multivariant epitaxy where all of the grains have a single orientation relationship to the substrate. Subsequent interdiffusion between TiO2 and LiNb3O8 produces a solid solution with the rutile structure which, at these temperatures, appears to coexist in equilibrium with the underlying lithium niobate substrate. This rutile solid solution serves as the source of Ti in the final stage of interdiffusion, which occurs only at higher temperatures (≳ 1000 °C), and leads to consumption of the rutile layer by the substrate. Structural models are discussed for epitaxial grain growth and interdiffusion.

Investigation of the Sintering Behavior of Ultrapure α-Alumina Containing Low Amounts of SiO2 or CaO

2006 ◽  
Vol 317-318 ◽  
pp. 1-6 ◽  
Author(s):  
Nicolas Louet ◽  
Thierry Epicier ◽  
Gilbert Fantozzi
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Oxygen Vacancies ◽  
Glassy Phase ◽  
Intermediate Stage ◽  
Abnormal Grain Growth ◽  
Sintering Behavior ◽  
Critical Temperatures ◽  
Heterogeneous Microstructures

The target of this work is to investigate the effect of small additions of SiO2 or CaO on the sintering behavior and the microstructure of an ultrapure α-alumina compound. The sintering behavior has been investigated through extensive dilatometric study. SiO2 additions lead to a significant decrease in shrinkage rate during the intermediate stage of sintering whereas CaO is beneficent to densification. It has been found that during this stage which corresponds to the maximum of densification rate, grain boundaries diffusion controls densification through oxygen vacancies. The study of the densification behavior under different atmospheres help us to explain the role of the additives in agreement with electroneutrality equations. S.E.M. investigations confirm the well know correlation between doping and heterogeneous microstructures. After doping with SiO2 or CaO, abnormal grain growth appears at temperatures corresponding to the lowest eutectics given by Al2O3-SiO2 or Al2O3-CaO phase diagrams. H.R.T.E.M. observations show that below the critical temperatures for abnormal grain growth, additives enrichment is observed near grain boundaries (GBs). Above these temperatures, glassy phase for SiO2-doping and calciumhexaluminate (CA6) for CaO-doping are present at grain boundaries.

Nucleation and Abnormal Grain Growth of Alpha-A12O3 in Gamma-Alumina Matrix

1991 ◽  
Vol 230 ◽  
Author(s):  
T. C. Chou ◽  
T. G. Nieh
Keyword(s):  
Grain Growth ◽  
Boundary Migration ◽  
Abnormal Grain Growth ◽  
Alumina Matrix ◽  
Orientation Relationships ◽  
Nucleation Kinetics ◽  
Alumina Films ◽  
Transmission Electron ◽  
Average Grain Size ◽  
Sputter Deposited

AbstractThe microstructures of reactive sputter-deposited alumina films have been studied by transmission electron microscopy. The as-deposited films contained γ-A12O3 phase in an amorphous alumina matrix. Annealing of the films at 1200° C for 2 h resulted in nucleation and concurrent anomalous grain growth of α-A12O3 in a polycrystaUine γ-Al2O3 matrix which exhibited a layered microstructure and was strongly textured along [001]. The grain sizes of α-A12O3 varied from 3 to 20 μm, while the average grain size of γ-A12O3 was only about 50 nm. It appears that the nucleation kinetics of a-A12O3 was slow. As a result, the abnormal grain growth of α-A12O3 proceeded by consuming surrounding γ-Al2O3 grains. An atomic model is presented to explain the origin of layered structure in γ-A12O3. The nucleation mechanism of a-A12O3 in γ-alumina matrix is suggested. Orientation relationships between γ- and α-A12O3 are reported. The anomalous grain growth of α- A12O3 is discussed in terms of γ/α interface boundary migration.

Grain Boundary Responses to Local and Applied Stress: An In Situ TEM Deformation Study

2006 ◽  
Vol 976 ◽  
Author(s):  
Bryan Miller ◽  
Jamey Fenske ◽  
Dong Su ◽  
Chung-Ming Li ◽  
Lisa Dougherty ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Transmission Electron Microscope ◽  
In Situ Tem ◽  
Deformation Twins ◽  
Transmission Electron ◽  
Dislocation Interactions

AbstractDeformation experiments at temperatures between 300 and 750 K have been performed in situ in the transmission electron microscope to investigate dislocation interactions and reactions with grain boundaries and other obstacles. Dislocations, both partial and perfect, as well as deformation twins have been observed being emitted from grain boundaries and, in some cases, even the same grain boundary. The ejection of dislocations from the grain boundary can result in its partial or total annihilation. In the latter case, the disintegration of the grain boundary was accompanied by grain growth and a change in misorientation.

Abnormal grain growth of sputtered CuNi(Mn) thin films

2000 ◽  
Vol 15 (5) ◽  
pp. 1062-1068 ◽  
Author(s):  
W. Brückner ◽  
V. Weihnacht ◽  
W. Pitschke ◽  
J. Thomas ◽  
S. Baunack
Keyword(s):  
Thin Films ◽  
Grain Growth ◽  
Abnormal Grain Growth ◽  
Temperature Cycle ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Columnar Grains ◽  
Maximum Temperatures ◽  
Film Substrate ◽  
20 Nm

The evolution in both stress and microstructure was investigated on sputtered Cu0.57Ni0.42Mn0.01thin films of 400 nm thickness during the first temperature cycle up to 550 °C. Samples from stress–temperature measurements up to various maximum temperatures were analyzed by x-ray diffraction, scanning and transmission electron microscopy, and Auger electron spectroscopy. The columnar grains with lateral diameters of about 20 nm in the as-deposited state coarsen to about 400 nm above 300 °C. Probably due to the impurity (Mn) drag effect, the coarsening occurs by abnormal grain growth rather than by normal grain growth, starting near the film–substrate interface. The stress development results from a combination of densification due to grain growth and plastic stress relaxation.

scholarly journals An in situ transmission electron microscope investigation into grain growth and ordering of sputter-deposited nanocrystalline Ni3Al thin films

2002 ◽  
Vol 17 (8) ◽  
pp. 2085-2094 ◽  
Author(s):  
H. P. Ng ◽  
A. H. W. Ngan
Keyword(s):  
Electron Microscope ◽  
Grain Growth ◽  
Transmission Electron Microscope ◽  
Growth Kinetics ◽  
Abnormal Grain Growth ◽  
Face Centered Cubic ◽  
Transmission Electron ◽  
Sputter Deposited ◽  
Grain Growth Kinetics

The grain growth kinetics and ordering behavior of direct-current magnetron sputter-deposited Ni75at.%Al25at.% alloy films were investigated using in situ isothermal annealing in a transmission electron microscope. Both normal and abnormal grain growth modes were observed. The normal grain growth kinetics under isothermal heating from 300 to 700 °C were found to comply with the Burke law d = K/dn−1, where d is grain size and K and n are constants with respect to time. The grain boundary mobility parameter K was found to obey an Arrehnius rate law with an apparent activation energy of 1.6 eV, and n was found to increase gradually from 5.2 at 300 °C to 8.7 at 700 °C. Abnormal grain growth occurred at 500 °C or higher, and grain coalescence was identified as an important operative mechanism. It was also observed that the initially as-deposited state of the films was crystalline with a disordered face-centered-cubic structure, but ordering into the equilibrium L12 intermetallic structure followed from annealing at temperatures above approximately 500 °C.

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