Competitive Role of Impurities on the Electrical Activity of as-grown Σ=13, Σ=25 and Deformed Σ=9 Grain boundaries in p-type Silicon Bi-crystals

2012 ◽  
Vol 1474 ◽  
Author(s):  
S. Gaiaschi ◽  
A. El Kouadri Boudjelthia ◽  
G. Regula ◽  
N. Burle ◽  
A. Mesli ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Before And After ◽  
Electron Beam Induced Current ◽  
Gold Diffusion ◽  
P Type ◽  
Czochralski Process ◽  
Probe Measurements ◽  
Good Agreement

ABSTRACTElectrical properties of grain boundaries grown by Czochralski process were studied by microwave phase shift (μW-PS) and electron beam induced current (EBIC), before and after gold diffusion at 700°C. As-grown samples had similar doping levels determined by four-point probe measurements but somewhat different oxygen concentrations, obtained by Fourier transform infrared spectroscopy (FTIR). It is shown that the increase of the grain boundary activity due to Au gathering at this planar defect can be hindered by native impurities (likely oxygen). EBIC and μW-PS techniques gave respectively electron diffusion lengths and lifetime values, both in good agreement. EBIC images on deformed Σ =9 showed that extrinsic dislocations do not activate the grain boundary at 300K.

Mechanisms of ductility improvement in L12 compounds

1988 ◽  
Vol 3 (3) ◽  
pp. 426-440 ◽  
Author(s):  
Osamu Izumi ◽  
Takayuki Takasugi
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Intermetallic Compounds ◽  
Present Article ◽  
Electronic Structures ◽  
Alloying Effect ◽  
Test Environment ◽  
Materials Development

The present article first describes some characteristics of structure, chemistry, and electronic (bond) nature for grain boundaries in the A3B Li2-type intermetallic compounds. Next, the phenomenological aspects for the grain boundary brittleness of the Li2-type intermetallic compounds are reviewed with respect to the combination of the constituent atoms, the alloying effect, the stoichiometry effect, and a role of impurity or gaseous atoms. It is emphasized that the brittleness of grain boundaries in the intermetallic compounds is directly controlled by the atomistic and electronic structures at grain boundary regions. Based on these systematic investigations, it is suggested that the brittleness of the Li2-type intermetallic compounds can be manipulated by appropriate control of composition and the corresponding electrochemical bond environment at grain boundary planes and by control of test environment. Furthermore, some examples of the materials development are described.

The Structure of Dislocations in Low-Angle Grain Boundaries in the Diamond Cubic Lattice

1981 ◽  
Vol 5 ◽  
Author(s):  
C.B. Carter
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Stacking Faults ◽  
Burgers Vector ◽  
Cubic Lattice ◽  
Partial Dislocations ◽  
Tilt Boundaries ◽  
P Type ◽  
Twist Boundaries

ABSTRACTDislocations in low-angle tilt boundaries exhibit a wide variety of Burgers vector including a/2<112> a<001> and a<111>. The dislocations are usually dissociated: Shohkley, stair-rod and Frank partial dislocations may each be formed together with associated intrinsic and extrinsic stackingfaults. Dislocations in low-angle {111} twist boundaries are usually assumed to dissociated by a glide mechanism to give two types of extended nodes, known as P–type and K–type, which contain intrinsic and extrinsic stacking-faults respectively. It is shown that dissociation by climb actually occurs for both types of grain boundary.

scholarly journals On the Role of Grain Boundaries During Sintering

2021 ◽  
Author(s):  
Torsten Staab ◽  
Ricardo Helm ◽  
Andreas Diegeler
Keyword(s):  
Mass Transport ◽  
Grain Boundaries ◽  
Average Distance ◽  
Intermediate Stage ◽  
Sintering Process ◽  
Positron Annihilation Lifetime ◽  
Boundary Signal ◽  
Increasing Temperature ◽  
Good Agreement

We present new results in positron annihilation lifetime spectroscopy (PALS), thermo-optical dilatometry and microscopy, which are indicating a strong correlation between grain-boundaries and mass transport during the sintering process of carbonyl iron powder. In this particular system we were able to show that the change in particle shape and size with increasing temperature yields an anisotropy in shrinkage, which manifests itself in a higher shrinkage perpendicular to the compaction axis. In the intermediate stage of sintering, where the major mass transport occurs, the average distance between two grain boundaries could be determined to (3,73 &plusmn; 0,18) &mu;m at T = 744&deg;C. This is in good agreement with previous calculations of positron pathways in defect free particles. Furthermore, due to sintering temperatures far above the annealing temperature of dislocations in iron, the existence of dislocations in the bulk of the particles is very unlikely. These claims are reflected by the collected positron data, which exhibit a clear grain boundary signal of &sim; 250ps while no vacancy or dislocation signal (typically &sim; 160 ps) is evident in the intermediate stage of sintering.

The role of microscopy in the alloy design of Ni- and Fe-based aluminides

1992 ◽  
Vol 50 (1) ◽  
pp. 168-169
Author(s):  
J.A. Horton
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Oxidation Resistance ◽  
Industrial Applications ◽  
Al Alloys ◽  
Ordered Alloys ◽  
Successful Control ◽  
Oxidation Resistant

During the last 10 years, there has been a resurgence of interest in ordered alloys for structural uses due to the discovery of the dramatic ductilizing effect of boron on grain boundaries in Ni3Al. With this discovery, it was hoped that the property of an increase in strength as the temperature is increased could be utilized as well as the excellent oxidation resistance. Now, alloys based on Ni3Al are in use in specialized industrial applications, such as high temperature forging dies and being tested for use as turbocharger rotors. Due to the successful control of the grain boundary strength in Ni3Al, other systems were reexamined. For example, Fe3Al was also thought to have inherently brittle grain boundaries, however it was found that with purer alloys the material failed by cleavage. Subsequently, development of practical, inexpensive, oxidation resistant alloys has proceeded. Fe3Al alloys are currently being tested for automobile exhaust applications.

Nanostructure, Nanochemistry and Grain Boundary Conductivity of Yttria-Doped Zirconia

2005 ◽  
Vol 106 ◽  
pp. 83-86
Author(s):  
A. Rizea ◽  
Jean Marc Raulot ◽  
C. Petot ◽  
Georgette Petot-Ervas ◽  
Gianguido Baldinozzi
Keyword(s):  
Grain Boundary ◽  
Beneficial Effect ◽  
Grain Boundaries ◽  
Strong Interaction ◽  
Glassy Phase ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
Boundary Conductivity ◽  
Comprehensive Study

This work was directed at a comprehensive study of the role of the nanostructure and nanochemistry on the transport properties of yttria-stabilized zirconia. Alumina additions lead to a decrease of sgb when the samples have clean grain boundaries, while sgb goes through a maximum in samples having glassy grain boundaries. The differences were attributed to the strong interaction between Al2O3 and SiO2 impurities leading to a glassy phase depletion at the grain-boundaries, due to a change in wettability. Moreover, XPS analyses show that Si and Y segregate near these interfaces according to a kinetic demixing process, explaining why a faster cooling rate after sintering has a beneficial effect on sgb.

Transient creep in fine-grained polycrystalline Al2O3 with Lu3+ ion segregation at the grain boundaries

2001 ◽  
Vol 16 (3) ◽  
pp. 716-720 ◽  
Author(s):  
Hidehiro Yoshida ◽  
Yuichi Ikuhara ◽  
Taketo Sakuma
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Testing Temperature ◽  
Grain Boundary Sliding ◽  
Transient Creep ◽  
Transient Time ◽  
Fine Grained ◽  
Boundary Sliding ◽  
The Difference ◽  
Good Agreement

The creep deformation in fine-grained polycrystalline Al2O3 is highly suppressed by the addition of 0.1 mol% LuO1.5. The transient creep behavior in Lu-doped Al2O3 was examined at the testing temperature of 1250–1350 °C, and the data were analyzed in terms of the effect of stress and temperature on the extent of transient time and strain. The experimental data on the transient creep in Lu-doped Al2O3 showed good agreement with the prediction from a time function of the transient and the steady-state creep associated with grain boundary sliding as well as an undoped one. The difference in the transient creep between Lu-doped and undoped Al2O3 can also be explained by the retardation of grain boundary diffusion due to the Lu3+ ions segregation in the grain boundaries.

Sign in / Sign up

Export Citation Format

Share Document