Electronic conductivity lets begin by comparing the

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: - Solid State Chemistry Ionic vs. Electronic Conductivity Let's begin by comparing the properties of ionic conductors with the conventional electronic conductivity of metals. Metals Conductivity Range = 10 S/cm < < 105 S/cm Electrons carry the current Conductivity Increases linearly as temperature decreases (phonon scattering decreases as T ) Conductivity Range = 10-3 S/cm < < 10 S/cm Ions carry the current Conductivity decreases exponentially as temperature decreases (activated transport) Chem 754 - Solid State Chemistry Solid Electrolytes 2 Defects In order for an ion to move through a crystal it must hop from an an occupied site to a vacant site. Thus ionic conductivity can only y onl occur if defects are present. The two simplest types of point defects are Schottky and Frenkel defects. Schottky Defect (i.e. NaCl) Na+ + Cl- Vna + VCl Frenkel Defect (i.e. AgCl) Ag+ VAg+ Ag+interstitial Chem 754 - Solid State Chemistry Ion Migration (Schottky Defects) Consider the movement of Na+ ions in NaCl via vacancies originating from Schottky defects. Note that the Na+ ion must squeeze through the lattice, inducing significant local distortion/relaxation. This is one factor that limits the mobility mobility of ions. A second factor that contributes is the relatively high high probability that the ion will jump back to it's original position, position,...
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online