The Concentration and Mobility of Vacancies in Sodium Chloride

Abstract

Articles you may be interested inEffect of concentration on the thermodynamics of sodium chloride aqueous solutions in the supercooled regime Dynamics of cavitation bubble induced by 193 nm ArF excimer laser in concentrated sodium chloride solutionsThe .electrical cond?-ctivity of sodium chloride, containing cadmium chloride as an impurity, has been ?etermme~ a~ a ~unction of tempe.rature. From these data it is calculated that the mobility of the positive IOn vacancies IS gIVen by the equation 11= (19600/T)exp( -9860/T) cm. 2 /volt-sec. between 250°C and 400°C !he concentration of positive ion vacancies in a "pure" sodium chloride crystal was 1.0X 10 17 cm-3 and mdependent of temperature below 550°C.

Ionic conductivity of pure and doped sodium chloride crystals

“…Despite minor differences in actual numbers, a pattern of consistency had now emerged in the diffusion measurements, but E,, must still be separated into i h s + Ah,, where hs is the enthalpy of Schottky defect formation and Ah,, the enthalpy of migration of an anion vacancy. Barr, Morrison, and Schroeder (24) used the then-determined experimental value of 2.02 eV for hs by Etzel and Maurer (26), which gave Ah,, = 0.91 eV. This value of hs is too low by current standards, so that 0.91 eV would be an upper bound.…”

Stabilizing NaCl particles with Cd2+ in a saturated solution during ex situ PSD measurement

“…In the solution containing small amounts of Cd 2þ and NaCl crystals, the Cd 2þ ions enter the Na þ lattice substitutionally on the surface of NaCl crystals. Since the crystal must be electrically neutral, each divalent impurity ion replaces two sodium ions with the result that an excess concentration of positive ion vacancies equal to the concentration of impurity ion is introduced into the crystal [7]. However, at low enough temperature the concentration of vacancies is so low that the impurity ions are mostly unassociated and permanently fixed at their positions in the lattice.…”

“…Cadmium was chosen as the divalent impurity because its ionic radius is within 5% of that of sodium [7][8][9][10]. Also the value of s à is determined not only by impurity concentration (number of impurity ions per mole of NaCl), but by its type as well.…”

“…The use of 100 ppm CdCl 2 was chosen to stabilize NaCl particles since Cd 2þ is known to adsorb on the crystal surface [6][7][8], pinning and immobilizing the steps in the surface of the NaCl crystal. Cadmium was chosen as the divalent impurity because its ionic radius is within 5% of that of sodium [7][8][9][10].…”

The thermal expansion of sodium chloride and some other alkali halides at high temperatures

“…However, the choice of a0 instead of c~99a does not eliminate the Lawson (1950) gives different values, the difference being due to misprints in Stelkow's paper, to the non-linearity of the plot of equation (2) and to the choice of a different temperature of fusion. f: Etzel & Maurer, 1950. g: In the case of Schottky defects, ~he volume expansion should be of the same order of magnitude as the concentration of defects; in the case of Frenkel defects, it should be less (cf.…”