Modification of chemical properties of iron cyanides in solid solutions

1968 ◽  
Vol 21 (9) ◽  
pp. 2175 ◽  
Author(s):  
JF Duncan ◽  
HJ Percival
Keyword(s):  
Solid Solutions ◽  
Point Defects ◽  
Alkali Halide ◽  
Chemical Properties ◽  
Host Lattices

The ions [Fe(CN)64-, [Fe(CN)63-, and [Fe(CN)5NO]2- have been incorporated as solid solutions in alkali-halide host lattices. For the hexacyanides, the CN stretch frequency is split in a manner which can be explained from C2v or D2h symmetry of the point defects introduced in the solid solutions. There is evidence of reduced species formed from [Fe(CN)6]3- and [Fe(CN)5NO]2-.

Defects in Crystals

1968 ◽  
Vol 26 ◽  
pp. 244-245
Author(s):  
Kenneth R. Lawless
Keyword(s):  
Electron Microscope ◽  
Point Defects ◽  
Surface Defects ◽  
Chemical Properties ◽  
Material Point ◽  
Crystal Defects ◽  
Defects In Crystals ◽  
Irradiation Effects ◽  
Normal Lattice ◽  
Line Defects

One of the most important applications of the electron microscope in recent years has been to the observation of defects in crystals. Replica techniques have been widely utilized for many years for the observation of surface defects, but more recently the most striking use of the electron microscope has been for the direct observation of internal defects in crystals, utilizing the transmission of electrons through thin samples.Defects in crystals may be classified basically as point defects, line defects, and planar defects, all of which play an important role in determining the physical or chemical properties of a material. Point defects are of two types, either vacancies where individual atoms are missing from lattice sites, or interstitials where an atom is situated in between normal lattice sites. The so-called point defects most commonly observed are actually aggregates of either vacancies or interstitials. Details of crystal defects of this type are considered in the special session on “Irradiation Effects in Materials” and will not be considered in detail in this session.

Non-Stoichiometric Compounds Derived From Point Defects

1994 ◽  
Author(s):  
Koji Kosuge
Keyword(s):  
Point Defects ◽  
Stoichiometric Composition ◽  
Pressure Gauge ◽  
Chemical Properties ◽  
Phase Rule ◽  
Chemical Balance ◽  
Long Time ◽  
Oxygen Gas ◽  
Pump Pressure ◽  
The One

In this chapter, we discuss ‘classical’ non-stoichiometry derived from various kinds of point defects. To derive the phase rule, which is indispensable for the understanding of non-stoichiometry, the key points of thermodynamics are reviewed, and then the relationship between the phase rule, Gibbs’ free energy, and non-stoichiometry is discussed. The concentrations of point defects in thermal equilibrium for many types of defect structure are calculated by simple statistical thermodynamics. In Section 1.4 examples of non-stoichiometric compounds are shown referred to published papers. The technical term ‘non-stoichiometric compounds’ has been used for a long time, in contradiction to the term ‘stoichiometric compounds’. The existence of non-stoichiometric compounds, which have also been called Bertholides compounds, cannot be explained from the law of definite proportion in its simplest meaning. Proust insisted that only stoichiometric compounds (also named Daltonide compounds) existed, whereas Bertholet maintained the existence of not only stoichiometric compounds but also non-stoichiometric compounds. This is a very famous argument in the history of chemistry. In the early years of the twentieth century, Kurnakov investigated the physical and chemical properties of intermetallic compounds in detail and found that the maximum or minimum in melting point, electrical resistivity, and also in the ordering temperature of lattices does not necessarily appear at the stoichiometric composition. An important discovery of Dingman was that stoichiometric FeO1.00 is non-existent under ordinary conditions. (At present, we can synthesize stoichiometric FeO1.00 under high pressure.) Non-stoichiometry, which originates from various kinds of lattice defect, can be derived from the phase rule. As an introduction, let us consider a trial experiment to understand non-stoichiometry (this experiment is, in principle, analogous to the one described in Section 1.4.8). Figure 1.1 shows a reaction vessel equipped with a vacuum pump, pressure gauge for oxygen gas, pressure controller for oxygen gas, thermometer, and chemical balance. The temperature of the vessel is controlled by an outer-furnace and the vessel has a special window for in-situ X-ray diffraction. A quantity of metal powder is placed on the chemical balance, and then the vessel is evacuated at room temperature.

Fascinating Alkali Halide Structures of Different Dimensionalities Incorporated in Host Lattices

2000 ◽  
Vol 39 (19) ◽  
pp. 3470-3473 ◽  
Author(s):  
R. Vaidhyanathan ◽  
S. Neeraj ◽  
P.A. Prasad ◽  
Srinivasan Natarajan ◽  
C.N.R. Rao
Keyword(s):  
Alkali Halide ◽  
Host Lattices

scholarly journals Study of Alkali Halide Solid Solutions by Scanning Electron Microscopy and X-ray Diffraction

2017 ◽  
Vol 23 (S1) ◽  
pp. 934-935
Author(s):  
R. Rodriguez-Mijangos ◽  
O. Hernández-Negrete ◽  
R. C. Carrillo-Torres ◽  
F. J. Carrillo-Pesqueira ◽  
M. E. Alvarez-Ramos ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Solid Solutions ◽  
Alkali Halide ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron
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