Ionic solid, electrical conductivity

Electrical conductivity of metals is very high and is of the order of 106 108 ohm-1 cm-1 while that of insulators is of the order of 10-12 ohm-1 cm-1. Semi-conductors have intermediate conductivity which lies in the range 102 10-9 ohm-1 cm1. Electrical conductivity of solids may arise through the motion of electrons and positive holes (electronic conductivity) or through the motion of ions (ionic conductivity). The conduction through electrons is called n-type conduction and through positive holes is called p-type conduction. Pure ionic solids where conduction can take place only through motion of ions are insulators. However, the presence of defects in the crystal structure increases their conductivity. 

These criteria for the ideal insertion material were questioned at the beginning of the 2000s with the arrival of nanomaterials for which the Laboratoire de Reactivite et Chimie des Solides (LRCS) [POI 01] was a pioneer. Along with the structure and composition, size was the third parameter it was possible to recover many materials previously neglected due to poor ionic and electric conductivity or to uncover new reaction mechanisms that did not require lacvmar compovmds. The benefits offered by nanoscale and nanostructured materials to Li-ion technol( are now so numerous that we will provide only the three best examples. 

When a voltage is applied to a piece of metal, an electric current flows in it because the delocalised electrons (mobile electrons) are free to move. Metallic bonding is the only type of bonding that allows us to predict reliably that a solid will conduct electricity. Covalent solids cannot conduct electricity because none of their electrons are free to move, although graphite is an exception to this. Ionic solids cannot conduct because neither their electrons nor their ions are free to move. 

Electrical properties of liquids and solids are sometimes crucially influenced by H bonding. The ionic mobility and conductance of H30 and OH in aqueous solutions are substantially greater than those of other univalent ions due to a proton-switch mechanism in the H-bonded associated solvent, water. For example, at 25°C the conductance of H3O+ and OH are 350 and 192ohm cm mol , whereas for other (viscosity-controlled) ions the values fall... 

Electrolyte a substance, liquid or solid, which conducts electrical current by movement of ions (not of electrons). In corrosion science, an electrolyte is usually a liquid solution of salts dissolved in a solvent, or a molten salt. The term also applies to polymers and ceramics which are ionically conductive. 

When an ionic solid such as NaCl dissolves in water the solution formed contains Na+ and Cl- ions. Since ions are charged particles, the solution conducts an electric current (Figure 2.12) and we say that NaCl is a strong electrolyte. In contrast, a water solution of sugar, which is a molecular solid, does not conduct electricity. Sugar and other molecular solutes are nonelectrolytes. 

Ionic solids do not conduct electricity because the charged ions are fixed in position. They become good conductors, however, when melted or dissolved in water. In both cases, in the melt or solution, the ions (such as Na+ and Cl-) are free to move through the liquid and thus can conduct an electric current. 

When we study a solid that does not have the characteristic lustrous appearance of a metal, we find that the conductivity is extremely low. This includes the solids we have called ionic solids sodium chloride, sodium nitrate, silver nitrate, and silver chloride. It includes, as well, the molecular crystals, such as ice. This solid, shown in Figure 5-3, is made up of molecules (such as exist in the gas phase) regularly packed in an orderly array. These poor conductors differ widely from the metals in almost every property. Thus electrical conductivity furnishes the key to one of the most fundamental classification schemes for substances. 

When an ionic solid like sodium chloride is melted, the molten salt conducts electric current. The conductivity is like that of an aqueous salt solution Na+ and Cl- ions are present. The extremely high melting temperature (808°C) shows that a large amount of energy is needed to tfear apart the regular NaCl crystalline arrangement to free the ions so they can move. 

Ionic bond, 287, 288 dipole of, 288 in alkali metal halides, 95 vs. covalent, 287 Ionic character, 287 Ionic crystal, 81, 311 Ionic radius, 355 Ionic solids, 79, 81, 311 electrical conductivity, 80 properties of, 312 solubility in water, 79 stability of, 311... 

Measurements of electrical conductivity permit the identification of the charge-carrying species in the solid phase and also the detection of ionic melts [111,417]. Bradley and Greene [418], for example, could determine the kinetics of reactions between Agl, KI and Rbl because the product (K, Rb)Ag4Is had a considerably higher conductivity than the reactants. The conductivity of the reactant mixture was proportional to the thickness of the product layer. 

All metals conduct electricity on account of the mobility of the electrons that bind the atoms together. Ionic, molecular, and network solids are typically electrical insulators or semiconductors (see Sections 3.f3 and 3.14), but there are notable exceptions, such as high-temperature superconductors, which are ionic or ceramic solids (see Box 5.2), and there is currently considerable interest in the electrical conductivity ol some organic polymers (see Box 19.1). 

The effect of water salinity on crop growth is largely of osmotic nature. Osmotic pressure is related to the total salt concentration rather than the concentration of individual ionic elements. Salinity is commonly expressed as the electric conductivity of the irrigation water. Salt concentration can be determined by Total Dissolved Solids (TDS) or by Electrical Conductivity (EC). Under a water scarcity condition, salt tolerance of agricultural crops will be the primordial parameter when the quality of irrigation water is implicated for the integrated water resources management [10]. 

The presence of ions in solution is what gives a sodium chloride solution the ability to conduct electricity. If positively and negatively charged wires are dipped into the solution, the ions in the solution respond to the charges on the wires. Chloride anions move toward the positive wire, and sodium cations move toward the negative wire. This directed movement of ions in solution is a flow of electrical current. Pure water, which has virtually no dissolved ions, does not conduct electricity. Any solution formed by dissolving an ionic solid in water conducts electricity. Ordinary tap water, for example, contains Ionic Impurities that make It an electrical conductor. 

An important developing area that lies in the region between polymer chemistry, ceramic science, and metals, involves the search for new electrically-conducting solids. Linear polymers may conduct electricity by electronic or ionic mechanisms. As will be discussed, polyphosphazenes have been synthesized that, depending on the side group structure, conduct by either of these two processes. 

FIGURE 3.9 The electrical conductivity of La1 xSrxCo03 3in air as a function of Sr doping, x. (From Petrov, A.N. et al., Solid State Ionics, 80 189-199, 1995. With permission.)... 

Zhong H-H, Zhou X-L, Liu X-Q, and Meng G-Y. Synthesis and electrical conductivity of perovskite Gd1 ICaICr03 (0Sx 0.3) by auto-ignition process. Solid State Ionics 2005 176 1057—1061. 

Yasuda I and Hishinuma M. Electrical conductivity and chemical diffusion coefficient of Sr-doped lanthanum chromites. Solid State Ionics 1995 80 141-150. 

Tsoga A, Naoumidis A, and Stover D. Total electrical conductivity and defect structure of Zr02-Ce02-Y203-Gd203 solid solutions. Solid State Ionics 2000 135 403M09. 

We shall briefly discuss the electrical properties of the metal oxides. Thermal conductivity, electrical conductivity, the Seebeck effect, and the Hall effect are some of the electron transport properties of solids that characterize the nature of the charge carriers. On the basis of electrical properties, the solid materials may be classified into metals, semiconductors, and insulators as shown in Figure 2.1. The range of electronic structures of oxides is very wide and hence they can be classified into two categories, nontransition metal oxides and transition metal oxides. In nontransition metal oxides, the cation valence orbitals are of s or p type, whereas the cation valence orbitals are of d type in transition metal oxides. A useful starting point in describing the structures of the metal oxides is the ionic model.5 Ionic crystals are formed between highly electropositive... 

These forces affect the boiling point, melting point, hardness, and electrical and heat conductivity of a substance. In this chapter, we will study metals, ionic solids, network solids, dipole-dipole attractions, van der Waals forces and hydrogen bonds. 

In ionic solids, electrons are held in place around the ions so they don t conduct electricity. However, in aqueous solution and molten state, they do conduct electricity. Electrical conductance of ionic compounds is not due to movement of electrons but to the movement of ions. 

KC1, NaNOs and LiF are ionic solids. Ionic solids don t conduct electricity in the solid state, however, aqueous solutions and molten forms of ionic compounds contain mobile ions so they can conduct electricity Thus, aqueous KC1 and LiF conduct electricity but solid NaN03 doesn t. 

Aqueous soap solutions can be obtained in three distinct forms, the sol form containing the ionic micelle, a clear gel, and a white opaque solid the curd. The sol and gel forms of various soaps have been examined by McBain and his co-workers and shown to differ only in elasticity and rigidity, whilst the electrical conductivity, refractive index, concentration of metallic ion and lowering of the vapour pressure are all identical, results to be anticipated on the fibrillar theory. The gel as we have seen is fibrillar in nature and the conversion of a gel into a curd is brought about by the removal of soap fi om solutions in the form of relatively coarse fibres, a process similar to crystallisation. The experiments of Laing and McBain... 

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