Junction grain boundary

Effects due to grain boundaries have been discussed by Chartier et al. [93] with respect to the CdS/polysulfide junction. The photoelectrochemical behavior of polycrystalline CdS layers obtained by the spraying technique was found to be... 

Grain boundaries form junctions between grains within the particle, due to vacancy and line-defect formation. This situation arises because of the 2nd Law of Thermodjmamics (Entropy). Thus, if crystallites are formed by precipitation from solution, the product will be a powder consisting of many small particles. Their actual size will depend upon the methods used to form them. Note that each crystallite can be a single-crystal but, of necessity, will be limited in size. 

Figure 6.11 (a) Definition of the dihedral angle, , at a junction of three grain boundaries in a polycrystalline solid, (b) Schematic illustration of the shape of an inclusion phase for different dihedral angles. 

One of the features first observed in BaPbj B Og, and now known as a hallmark of bulk ceramic superconductors is the appearance of grain boundary Josephson junctions. One of the most... 

With the additional possibility of electrostatic coupling and charging of grain boundaries to modify the properties of the JJ s (48), it is attractive to consider the use of these JJ s in microelectronics, perhaps for on chip optical or microwave Josephson Junction communications. 

However, Plateau s laws are not obeyed by the grain boundary structure in the special polycrystal in Fig. 15.15. To achieve local equilibrium at all grain junctions, so that Plateau s laws are obeyed, the faces of each grain must be curved [31]. A boundary structure in which all junctions obey Plateau s laws is presented in Fig. 15.16, which shows a polycrystal consisting of six grains that meet at four vertices. Each grain fully occupies one face of the polycrystal. As in Fig. 15.15,... 

These conditions are Young s equation, qi/sin i = 72/sind>2 = 73/singrain-boundary angles to be 27r/3 for the uniform boundary-energy case and the requirement that quad- and higher-order junctions are unstable in two dimensions [30]. 

Microstructures are generally too complex for exact models. In a polycrystalline microstructure, grain-boundary tractions will be distributed with respect to an applied load. Microstructures of porous bodies include isolated pores as well as pores attached to grain boundaries and triple junctions. Nevertheless, there are several simple representative geometries that illustrate general coupled phenomena and serve as good models for subsets of more complex structures. 

TEM micrograph of a Cu-Al203 nanocomposite. The Cu particles are elongated and located at grain boundaries and triple junctions. 

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