Home > Uncategorized > Introduction to Solid State Chemistry Lecture 18

Introduction to Solid State Chemistry Lecture 18

Overview
This class doesn’t have tests; it has celebrations of learning. Today’s lecture is on point defects. The regular teacher was getting vetted by the SS to meet POTUS. Apparently his education included time in Toronto.

Details
Crystals are like people, it’s the defects that make them interesting. Two errors are chemical and atomic arrangement/structure. Errors may be profitable and dopands or bad and impurities.

0D point defect
1D line
2D interphase
3D bulk

Point defects are localized disruptions in reguarity. One and between lattice sites. Substitutional impurities occupy normal lattice sites. Dopants like B or P. Alloying elements like Mg in Al, comtaminants like Li. Interstitial impurities occupy positions between lattice sites, contaminants like H in Fe, alloys like C in Fe. Hydrogen enters La-Ni complexes. Vacancy is an unoccupied lattice site, formed at the time of crystallization, formed in serivce under extreme conditions.

Breaking bonds costs energy, making bonds releases energy. It costs energy to make vacancy in materials. At finite temperature, thermal vacancies created.

Fraction of Vacant Sites:
nv (vacancies per unit volume)/(number of atomic sites per unit volume)
=A e (vacancy formation energy/thermal energy at temp of interest)
A = 0.1 – 10

For Cu at RT,
Nv = 1.1 e^(-1.03/Kb x 300)=2.19 x 10^-19
10^5 vacancies / cm3

At melting point of Cu, 1085C, Nv=1.67 x 10^-4

Atomix is a little shaker thing with bubbles inside of it. Approximates a real xstl.

Ionic crystal point defects must maintain global charge neutrality. Schottky imperfections are formation of equivalent numbers of cationic and anionic valences. Frenkel imperfections are formations of ionic vacancies and and ion interstitial; in crystals with very different atomic radii. . F center forms an ion vacancy adn a bound electron.

ZrO2 = VZr + 2Vo2

Dislocations are line defects in 2D. Dislocations in fingerprints are common. They help materials deform easily.

Review

IE 13 electron acceptor, electrophile, nonmetal.

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