Structure.homework-#7 answer - x is a small fractional...

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MTLE-2100 Structure of Engineering Materials, Homework #7 --Answer 1. Calculate the theoretical density of the following materials. a) CaO-stabilized ZrO 2 Zr 0.80 Ca 0.20 O 1.80 Fluorite structure, cubic a=5.124 Å , oxygen vacancy d={4x0.8x91.22+4x0.2x40.08+8x(1.80/2.0)x16}/{(5.124) 3 x 10 -24 x6.02x10 23 }=439.168/80.989=5.42g/cm 3 b) Wustite, Fe 0.91 O Rock salt structure, a = 4.282 Å , cation vacancy d = {4x0.91x 55.85 +4x16}/(4.282) 3 x10 -24 x6.02x10 23 =267.294/47.265=5.66g/cm 3 2. Predict the conduction type (n-type or p-type) of the following non-stoichiometric compounds
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Unformatted text preview: x is a small fractional number a) Co 1-x O In a stoichiometric compound, CoO, cobalt would take 2+ valence. Since Co deficient, some cobalt would increase their valence to 3+. Tri-valent Co 3+ could change Co 3+ Co 2+ + h • p-type semiconductor b) WO 3-x In a stoichiometric compound, WO 3 , tungsten would take 6+ valence. Since oxygen is deficient, some tungsten would reduce their valence to 5+. W 5+ could change W 5+ W 6+ + e’ n-type semiconductor...
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