imperfection of solid & atom movements
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Imperfection of Solid & Atom movements
Subject: Elektrokimia Fasa Padatan
Dr. Fitria Rahmawati
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IMPERFECTION IN SOLID
Ideal solid does not exist, all contain defects
or imperfection.
Many defects available:1. Point defect
2. Linear defect3. Interfacial defect (boundaries)
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1. Point Defect:There are two types of point defect based on its
process of defect formation:1. intrinsic defect
the increase of entropy of crystal
2. extrinsic defect
defect which may occur in isolation in order
to balance the presence of impurity
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Intrinsic Point Defect Schottky Defect
Schottky defect consist of charge balancingcation and anion vacancies.
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Frenkel Defect
a defect due to atoms at interstitial position or a
place outside normal position.
Cation is displaced from normal to interstitial lattice
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Frenkel cation defect is more common due to
smaller size of cation hence easier to beoccomodated in interstitial site
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Color Centres Electrons are trapped in vacant sites give rise to
color materials
Trapped electrons can be made by:
1. irradiation of the sample
Irradiation can lead defect where an electron has beenadded or losed
2. treatment with an electron donor like sodium or
potassium donor Treatment with alkali metal vapour could produce electron
excess in material
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F, H and V Color Centres
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Application of color centre of BaFBr:Eu2+ phosphors in medical X-ray
analysis
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Extrinsic point defect Extrinsic defect will be produced when a cationic impurities or
dopants are introduced into solid however the dopant does not
have the same valence as cation which has been replaced. Examples:
Fe1-x O : cation vacancies
Ca2+ in ZrO2 : anion vacanciesY3+ in ZrO2 : anion vacancies
Ca2+ or Cd2+ in NaCl : cation vacancies
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Crystal structure of Fe1-xO
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Real crystals may contain both intrinsic and
extrinsic defect. The dominant defect depends
upon temperature and doping level
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2. Linear defect (Line defect)Line defect or dislocation mainly caused by the absence of ions in
a line structure or named as mis-alignment, or because of the
existence of vacancies along the line, these defect is called asedge dislocation. When the mis-alignment lead to the
movement of a block of ions gradually upward or downward, it
as screw dislocation (Rahmawati, 2012)
This defect can occur due to:
-mechanical stress and deformation
- unperfected crystal growing
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Most dislocation have mixes edge and screwcharacter
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3. Interfacial DefectInterfacial Defect is boundaries that have two dimensions and
normally separate regions of the materials that have different
crystal structures and / or different crystallographic orientation
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ATOM MOVEMENTS
(Rahmawati, 2012)
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(Rahmawati, 2012)
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References: Callister, W. (2000) Material Science and Engineering: An
Introduction, 5th edition, John Wiley & Sons, Inc., New Jersey.
De Guire, M.R. (2003) Introduction to Materials Science &Engineering, EMSE 201.
Effendy (2008) IKATAN IONIK dan cacat-cacat pada kristal ionik,
edisi 2, bayumedia Publishing, Malang. Rahmawati, F. (2012) Zirconia-LSGM Based Materials as
Electrolyte for SOFC, the mixtured materials for solid electrolyte,
LAP LAMBERT academic Publishing, Saarbrken, Germany. West, A. (1999) Basic Solid State Chemistry, second edition,
John Wiley & Sons, Ltd., Chichester, Ohio.