Defect Concentration: Vacancies in Metals ny =N exp (-AHv)/kT) 4Hny≈1eV T=300K n,/N0≈10-18 too small to be measured T=1200K n/No≈105 measurable Arrhenius plot In ny=In No-PH)/kT slope =-H/kT Higher T→more defects Lower AH→more defects 士1T
Defect Concentration: Vacancies in Metals nv = N exp (- ∆Hf(v) / kT ) ∆Hf(v) ≈ 1 eV T = 300 K nv / N0 ≈ 10-18 too small to be measured T = 1200 K nv / N0 ≈ 10-5 measurable ln nv = ln N0 - Hf(v) / kT Higher T more defects Lower ∆Hf more defects
空位的迁移能 空位的迁移能与晶体的结构有关： ●面心立方晶体： Ev≈E, ·体心立方晶体： E、 2 ●金刚石结构Si,Ge) E 10
ぎԡⱘ䖕⿏㛑 ぎԡⱘ䖕⿏㛑Ϣԧⱘ㒧ᵘ᳝݇ : 䴶ᖗゟᮍԧ : ԧᖗゟᮍԧ : 䞥߮㒧ᵘ ( S i , G e ) Em v ≈ Ev Em v Ev 2 1 ≈ Em v Ev 1 0 1 ≈
Diffusion 类似地，扩散系数D,由下式给出： -Ep kgT where Ep is the energy of diffusion and Do is a diffusion constant specific to the element. Strictly this applies only to self-diffusion,that is diffusion in an elemental substance
Diffusion ㉏Ԑഄ, ᠽᬷ㋏᭄ D, ⬅ϟᓣ㒭ߎ: − = k TE D D exp B D O where ED is the energy of diffusion and DO is a diffusion constant specific to the element. Strictly this applies only to self-diffusion, that is diffusion in an elemental substance.
Quenching(淬火) 温度越高，空位浓度越大.采用淬火的方法可以产生 过饱和的点缺陷.即将高温状态的晶体急剧冷却到低温 这样高温下处于热力学平衡的空位来不及扩散就被冻 结.但淬火方法一般不能把过饱和浓度的填隙原子冻结 因为填隙原子的迁移能太小. 这种缺陷可以引起附加的电阻： AR-Cn-CNexp C是比例常数
Quenching ⏀☿ ⏽ᑺ䍞催,ぎԡ⌧ᑺ䍞. 䞛⫼⏀☿ⱘᮍ⊩ৃҹѻ⫳ 䖛佅ⱘ⚍㔎䱋. ेᇚ催⏽⢊ᗕⱘԧᗹދ࠻ैࠄԢ⏽ , 䖭ḋ催⏽ϟ໘Ѣ⛁ᄺᑇ㸵ⱘぎԡᴹϡঞᠽᬷህ㹿ޏ 㒧. Ԛ⏀☿ᮍ⊩ϔ㠀ϡ㛑ᡞ䖛佅⌧ᑺⱘ฿䱭ॳᄤޏ㒧 , Ў฿䱭ॳᄤⱘ䖕⿏㛑ᇣ. 䖭⾡㔎䱋ৃҹᓩ䍋䰘ࡴⱘ⬉䰏: − ∆ = = k TE R Cn CN exp B V Cᰃ↨՟ᐌ᭄.
2.Interstitials(填隙) If the interstitial atom is the same size as the close packed atoms,then considerable disruption to the structure occurs. 00000O Again,this is a point defect and requires much energy Vacancy Interstitial
2. Interstitials ฿䱭 If the interstitial atom is the same size as the close packed atoms, then considerable disruption to the structure occurs. Again, this is a point defect and requires much energy