Abstract
Alumina (α-Al2O3) is one of the representative high-temperature structural materials. Dislocations in alumina play an important role in its plastic deformation, and they have attracted much attention for many years. However, little is known about their core atomic structures, with a few exceptions, because of lack of experimental observations at the atomic level. Low-angle grain boundaries are known to consist of an array of dislocations, and they are useful to compose dislocation structures. So far, we have systematically fabricated several types of alumina bicrystals with a low-angle grain boundary and characterized the dislocation structures by transmission electron microscopy (TEM). Here, we review the dislocation structures in { 11 2 ¯ 0 } / [ 0001 ] , { 11 2 ¯ 0 } / 〈 1 1 ¯ 00 〉 , { 1 1 ¯ 00 } / 〈 11 2 ¯ 0 〉 , ( 0001 ) / 〈 1 1 ¯ 00 〉 , { 1 ¯ 104 } / 〈 11 2 ¯ 0 〉 , and ( 0001 ) / [ 0001 ] low-angle grain boundaries of alumina. Our observations revealed the core atomic structures of b = 1 / 3 〈 11 2 ¯ 0 〉 edge and screw dislocations, 〈 1 1 ¯ 00 〉 edge dislocation, and 1 / 3 〈 1 ¯ 101 〉 edge and mixed dislocations. Moreover, the stacking faults on { 11 2 ¯ 0 } , { 1 1 ¯ 00 } , and ( 0001 ) planes formed due to the dissociation reaction of the dislocations are discussed, focusing on their atomic structure and formation energy.
Highlights
A dislocation is one-dimensional lattice defect within a crystal structure
Pair contrasts are periodically arrayed with the interval of about 13.2 nm, suggesting that each dislocation is dissociated into two partial dislocations
These partial dislocations are separated along the 1120 plane, suggesting that a stacking fault on the 1120 plane is formed between the partial dislocations
Summary
A dislocation is one-dimensional lattice defect within a crystal structure. A dislocation is characterized by its Burgers vector and line direction. The Burgers vector represents the direction and magnitude of lattice distortion due to a dislocation, which is a critical parameter to determining the behavior of a dislocation, such as its slip direction and self-energy. Since the Burgers vector of a perfect dislocation must coincide with a lattice translation vector, the number of possible Burgers vectors is restricted in a crystal structure. In this sense, it should be efficient to characterize dislocation structures systematically in terms of Burgers vector in order to understand the dislocation behavior in a crystal
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