MSE_442_Lecture_16_Oct 30 2013

Brackets the concentrahons g is the free energy

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: - thermally generated in pure compounds; extrinsic defects – produced by external influences such as impuriHes and gaseous atmospheres 8 Kröger-Vink Notation q༇  the main symbol §༊  M - the parHcular type of atom, V- vacancy §༊  L - the site in the perfect laice at which the defect is located. §༊  The superscript C - the effecHve charge (or relaHve charge) q༇  Possible Defects in Al2O3 9 Defect Reactions q༇  Three conservaHon rules are observed §༊  ConservaHon of mass §༊  Electroneutrality §༊  Site raHo conservaHon q༇  let us consider the incorporaHon of MgO into Al2O3 §༊  SubsHtuHonal (Mg2+ à༎ Al3+) §༊  IntersHHal §༊  Self- compensaHng - both subsHtuHonal and intersHHal defects 10 Defect Concentration q༇  Assume a general reacHon q༇  At equilibrium at a fixed temperature, the law of mass acHon - the acHviHes of the reactants and products are equal to their concentraHons q༇  The equilibrium constant Law of Mass q༇  The brackets - the concentraHons, ΔG is the free energy change for the reacHon, R is the gas constant, and T is the absolute temperature q༇  For reacHons involving gaseous species, the concentraHon of a gas is taken as its parHal pressure 11 Intrinsic Defects Schogky Defect Frenkel Defect Electroneutrality 12 Extrinsic Defects – Nonstoichiometry q༇  EquilibraHon of ionic solids (e.g., an oxide MO) with an ambi...
View Full Document

This document was uploaded on 12/23/2013.

Ask a homework question - tutors are online