The existence of anti-phase domain boundaries (APBs) in polycrystalline materials is usually established by electron microscopic techniques (SEM/TEM) [1] and is also discussed in diffraction data analyses.[2]
I don’t have a good familiarity with TEM/SEM (and I’m very open to be educated here) but it doesn’t seem convincing enough to look at some microscopic images with atomic level resolution where APBs are found as a straight line (or arbitrarily curved line as in Figure 7 in ref. 1) forming a boundary/wall between the two domains in the same particles, while there is no disorderliness of any sort around and away from the APB.
The reason I’m raising this point is that particle surface is usually more disordered than any kind of defects in the bulk. In fact, it’s even well established that the surface of solid particles behave more or less like a liquid layer [3], and the smaller the particle size the thicker the liquid layer at the surface. And yet, in the TEM images of nanoparticles that I have seen in some articles there is(are) only the APB(s) visible, and no sign of the bigger unavoidable inherent surface disorder.
Is it possibly due to the fact that in TEM, the electrons pass through the particles and form an image which is influenced by the bulk of the particle? If so, why then the rest of the atomic arrangements within the domains look nearly perfect (i.e. as if it’s a single layer of pointy ordered atoms)?
And as for diffraction data, APBs affect some of the reflections selectively but usually there are different broadening contributions which make it challenging to disentangle. Nevertheless, at least the existence of planar defects like APBs is indicated in diffraction patterns.
Any input would be appreciated.
1) Article Antiphase Boundary Defects in Strontium Doped Lanthanum Scandate
2) Article Signature of antiphase boundaries in iron oxide nanoparticles
3) Article Observation of Surface Melting
Transmission electron microscopy (TEM) is a widely used technique for the characterization of materials at the nanoscale, including metal oxides. However, the reliability of TEM for the characterization of antiphase boundary (APB) defects in metal oxides depends on various factors, including the quality of the sample preparation, the type of microscope used, and the interpretation of the data.
In general, TEM can provide high-resolution images of APB defects in metal oxides, allowing their size, shape, and distribution to be determined. Additionally, TEM can provide information about the crystallographic orientation of the material and the atomic structure of the APB defect. This information can be used to understand the formation and behavior of APBs in metal oxides.
However, there are several challenges associated with the use of TEM for APB characterization in metal oxides. One challenge is the difficulty in preparing high-quality thin sections of the material for TEM analysis, particularly for complex or irregularly shaped materials. Another challenge is the potential for beam damage during TEM analysis, which can cause the material to undergo structural changes that may affect the observed APB defects.
Furthermore, the interpretation of TEM data can be complex, and it is important to use complementary techniques to confirm the observations made with TEM. For example, electron diffraction can be used to determine the crystallographic orientation of the material and confirm the location of APB defects observed by TEM.
In summary, TEM is a powerful technique for the characterization of APB defects in metal oxides, but its reliability depends on various factors, and care must be taken in sample preparation, data acquisition, and interpretation. When used appropriately and complemented by other techniques, TEM can provide valuable insights into the structure and behavior of APBs in metal oxides.
Jurabek Muzaffar ugli Abdiev, thank you for your answer. I think your answer is rather general about TEM (which is good to know) but my questions is more specific and about these domain boundaries (like ABP) under TEM. In a lot of cases, the surface of particles is disordered (the smaller the particle, the thicker the disordere layer). But there are TEM images with atomic resolutions and they show ABP defects. As far as I can say, surface disorder blurs the images. So how can those atomic resolutions be obtained without any blurring effect caused by the surface disorder?
Do you personally have experience with TEM-imaging of ABP?
You're correct that surface disorder can cause blurring in TEM images. However, in some cases, it's possible to obtain atomic-resolution images even for disordered surfaces. Here are a few factors that can contribute to this:
In summary, obtaining atomic-resolution images of disordered surfaces in TEM can be challenging, but it's possible under certain conditions. High electron energy, thin samples, careful imaging conditions, and surface preparation techniques can all contribute to achieving atomic resolution in these cases.
Polikristal malzemelere elektron mikroskobuyla bakıldığında kusurların farklı görünmesi metalin yapısından kaynaklanır. Çokkristalli malzemeler oksidasyon sırasında yapı olarak farklı sınır bölgelerine ayrılır. Bu bölgeler büyüklük ve yoğunluk bakımından önemlidir. Çünkü aynı şartlar altında oksidasyondan farklı şekilde etkilenirler. Oksidasyondan önce ve oksidasyondan sonra atom yoğunluklarının farklı olduğu bölgeler farklı kırılma indisine sahiptir. Bu bölgelerin atomik dizilişleri de önemlidir. Kütle önemli bir parametre değil, önemli olan oksidasyona uğrayan bölgenin oksidasyondan etkilenme derecesidir. Oksidasyon sırasında bazı sınır bölgelerdeki atomlar etkilenmeden çıkabilir.
Transmission electron microscopy (TEM) is a powerful technique for the characterization of antiphase boundary (APB) defects in metal oxides. However, the reliability of the technique depends on several factors.
One of the main challenges in the characterization of APB defects is their small size and the fact that they are often located within the bulk of the material. This makes it difficult to image them with conventional microscopy techniques. TEM overcomes this challenge by allowing for high-resolution imaging at the nanoscale.
However, the reliability of TEM in characterizing APB defects depends on several factors, including the quality of the sample preparation, the accuracy of the imaging parameters, and the experience and skill of the operator. Additionally, interpreting the TEM images to identify APB defects requires expertise in crystallography and image analysis.
In general, TEM is a reliable technique for the characterization of APB defects in metal oxides, but it requires careful sample preparation, imaging, and interpretation. Other complementary techniques, such as X-ray diffraction, scanning transmission electron microscopy (STEM), and atomic force microscopy (AFM), may also be used to provide additional information about the structure and properties of APB defects.
Alireza Badiei
Thank you for the general information. The specific part of the question is not addressed in the answers here though. Let's assume that the prepared sample is optimal, the operator is experienced and other conditions are met, how is it possible to capture a wall 'defect', dividing let's say the particle into two (seen as a line in the image), while there is no sign of surface disorder in the same image. Is it a matter of focusing on the defect and removing the blurring effect of surface defects?
It seems like imaging a not-very-disordered wall (APB) located under (and above) a large amount of surface disorder.
P.S. I have seen TEM data of amorphous surfaces which look quite blurry.
I apologize for the misunderstanding in my previous response. To answer your specific question, capturing a wall 'defect' (such as an APB) that is dividing a particle into two can be challenging, especially if there is a large amount of surface disorder that is blurring the image. Here are some possible strategies that can be used to capture such a defect:
In summary, capturing a wall 'defect' that is dividing a particle into two can be challenging, especially if there is a large amount of surface disorder. Using a combination of higher magnification, higher electron dose, different imaging modes, image processing techniques, and complementary techniques may help to capture the defect more clearly.
Dear Alireza Badiei
Thank you for the detailed answer. So, in principle it's possible but challenging.
I'm actually not going to be a TEM operator in the future (I'm not planning to), so I'll not need to know all the experimental problems and considerations. I mainly wanted to know how much I can rely on the data that I see in the literature (I gave a specific reference to an article in the question).
It's good anyways to have general information about it, so thank you for your time.
- Badges
- Science topic