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2.3 Calculation of thermal defect concentration课程教案、知识点、字幕

同学们好

上节课

Last class

介绍了缺陷反应方程式的书写

这节课

结合缺陷反应方程式

讲解热缺陷浓度的计算

并且是不断产生和消失的

在一定的温度下

当单位时间内产生和因复合而消失的缺陷数目相等时

系统就达到平衡

热缺陷的数目保持不变

类似于常见的化学反应平衡

我们可根据质量作用定律

利用化学平衡的方法计算缺陷的浓度

热缺陷浓度的计算直接使用下面的公式即可

我们来看公式中每一部分表示的含义

其中小n代表单位体积缺陷的个数

大N代表单位体积晶体中的总结点数

E就代表形成缺陷所需要的能量

大家要注意单位通常是电子伏特

计算时需要把它换算成焦耳

k是玻尔兹曼常数

直接使用即可

T代表绝对温度

使用时需换成换算成开氏温度

下面我们来看点缺陷的化学平衡

缺陷的产生和消失是一个动态的平衡

与化学反应一样

也可看成动态的化学平衡

因而采用化学平衡的方法计算缺陷的浓度

这里主要介绍Frenkel缺陷和Schottky缺陷的化学平衡

首先我们来看弗伦克尔缺陷

它的特点是质点离开原来的位置

进入间隙形成间隙原子

原来的位置形成空位

缺陷反应方程式如何书写呢

以溴化银晶体为例

方程式左边为

方程式左边为

正常结点的Ag+和未被占据的间隙

右边写Ag+进入间隙形成带正电荷的Agi• 和V'Ag

化学平衡常数可以用这个公式表示

即Agi• 和V'Ag浓度的乘积

除以正常结点Ag+浓度和未被占据空隙的浓度

由于空位和间隙原子是成对产生的

因而间隙Ag+浓度和空位Ag+的浓度相等

我们再看肖特基缺陷的化学平衡

对于离子晶体而言

正负离子同时迁移到表面

形成正负离子的空位

以氧化镁晶体为例

我们看形成Schottky缺陷时

缺陷反应式如何书写

方程式左边表示正常结点处的Mg2+和O2-

右边写MgS和 OS

下标S代表表面位置

同时形成VO•• 和 V''Mg

通常

迁移到表面的新质点与原表面的质点

没有本质区别

因而

Schottky缺陷反应式可简写为

左边正常无缺陷的晶体 右边是形成的空位

空位无质量这个反应式也满足书写规则

大家要注意

为保持电中性

正离子和负离子空位成对产生

所以二者的浓度也是相等的

所以二者的浓度也是相等的

同样带入平衡常数计算公式

计算Schottky缺陷的浓度

从以上讲解可以看出

Frenkel和Schottky缺陷的浓度计算公式

具有相同的形式

has the same form

热缺陷的浓度是

缺陷形成自由焓和温度的函数

他们之间的关系可归纳为

开始时介绍的浓度公式

温度越高

热缺陷浓度越大

我们来回顾一下这节课的内容

这节课主要以Frenkel缺陷和Schottky缺陷为例

介绍了缺陷浓度的计算

大家要掌握其计算方法

这节课就讲到这里

同学们再见

Fundamentals of Inorganic Materials Science课程列表:

1 Introduction

-Introduction

-introduction

-Test for chapter 1

2 Crystal Imperfection

-2.1 Type of defect

--2.1 Types of point defects

--2.1 Types of point defects

-2.2.1 The expression methods of point defects

--2.2.1 The expression methods of point defects

--2.2.1 The expression methods of point defects

-2.2.2 The rules for writing of defect reaction equation

--2.2.2 The rules for writing of defect reaction equation

--2.2.2 The rules for writing of defect reaction equation

-2.3 Calculation of thermal defect concentration

--2.3 Calculation of thermal defect concentration

--2.3 Calculation of thermal defect concentration

-2.4 Non-stoichiometric compounds

--2.4 Non-stoichiometric compounds

--2.4 Non-stoichiometric compounds

-Homework for chapter 2

-Test for chapter 2

3 Solid solution

-3.1 The classification of solid solutions

--3.1 The classification of solid solutions

--3.1 The classification of solid solutions

-3.2 Substitutional solid solution

--3.2 Substitutional solid solution

--3.2 Substitutional solid solution

-3.3 Interstitial solid solution

--3.3 Interstitial solid solution

--3.3 Interstitial solid solution

-3.4 The research method of solid solutions

--3.4 The research method of solid solutions

--3.4 The research method of solid solutions

-3.5 Questions for crystal imperfection and solid solution

--Questions for crystal imperfection and solid solution

-Homework for chapter 3

-Test for chapter 3

4 Melt and glass

-4.1 Melt structure

--4.1 Melt structure

--4.1 Melt structure

-4.2 The properties of the melt

--4.2.1 The properties of the melt_viscosity

--4.2.2 The properties of the melt_surface tension

--4.2 The properties of the melt

-4.3 The characteristics of glass

--4.3 The characteristics of glass

--4.3 The characteristics of glass

-4.4 The formation of glass

--4.4.1 The formation of glass_kinetics conditions

--4.4.2 The formation of glass_crystal chemical conditions

--4.4 The formation of glass

-4.5 The structure of glass

--4.5 The structure of glass

--4.5 The structure of glass

-4.6 The typical glass

--4.6 The typical glass

--4.6 The typical glass

-4.7 Questions for melt and glass

--Questions for melt and glass

-Test for chapter 4

5 Phase equilibrium

-5.1 Phase equilibrium in silicate systems

--5.1 Phase equilibrium in silicate system

--5.1 Phase equilibrium in silicate system

-5.2 One-component system phase diagram

--5.2 One-component system phase diagram

--5.2 One-component system phase diagram

-5.3 Applications of one-component diagrams

--5.3 Applications of one-component diagrams

--5.3 Applications of one-component diagrams

-5.4 Binary diagrams

--5.4.1 Binary diagram with eutectic point

--5.4.2 Binary system with a congruent melting compound and one with an incongruent melting compound

--5.4.3 Other five types of phase diagrams of binary systems

--5.4 Binary diagrams

-5.5 Applications of binary phase diagrams

--5.5 Applications of binary phase diagrams

--5.5 Applications of binary phase diagrams

-5.6 Ternary diagrams

--5.6.1 Representation of ternary system composition

--5.6.1 Representation of ternary system composition

--5.6.2 Three-dimensional state diagram and plane projection diagram of a simple ternary system

--5.6.2 Three-dimensional state diagram and plane projection diagram of a simple ternary system

--5.6.3 (1) Basic types of ternary phase diagrams

--5.6.3 (2) Basic types of ternary phase diagrams

--5.6.3 (3) Basic types of ternary phase diagrams

--5.6.3 Basic types of ternary phase diagrams

-5.7 Applications of ternary phase diagrams

--5.7 Applications of ternary phase diagrams

--5.7 Applications of ternary phase diagrams

-5.8 Research methods of phase equilibrium

--5.8 Research methods of phase equilibrium

--5.8 Research methods of phase equilibrium

-5.9 Questions for phase equilibria

--Questions for phase equilibria

-Homework for chaper 5

-Test for chapter 5

6 Diffusion

-6.1 Overview of diffusion

--6.1 Overview of diffusion

--6.1 Overview of diffusion

-6.2 The kinetic equations of diffusion

--6.2 The kinetic equations of diffusion

--6.2 The kinetic equations of diffusion

-6.3 The thermodynamic equation of diffusion

--6.3 The thermodynamic equation of diffusion

--6.3 The thermodynamic equation of diffusion

-6.4 Diffusion mechanisms and diffusion coefficient

--6.4 Diffusion mechanisms and diffusion coefficient

--6.4 Diffusion mechanisms and diffusion coefficient

-6.5 Diffusion in solid

--6.5 Diffusion in solid

--6.5 Diffusion in solid

-6.6 Factors affecting diffusion

--6.6 Factors affecting diffusion

--6.6 Factors affecting diffusion

-6.7 Questions for diffusion

--Questions for diffusion

-Homework for chaper 6

-Test for chapter 6

7 Solid state reactions

-7.1 Overview of solid state reactions

--7.1 Overview of solid state reactions

--7.1 Overview of solid state reactions

-7.2 Kinetic equation of solid state reaction

--7.2 Kinetic equation of solid state reaction

-7.3 Factors affecting the solid state reaction

--7.3 Factors affecting the solid state reaction

--7.3 Factors affecting the solid state reaction

-Homeword for chapter 7

8 Phase transformation

-8.1 The categories of phase transformation

--8.1 The categories of phase transformation

--8.1 The categories of phase transformation

-8.2 Crystallization

--8.2.1 Crystallization thermodynamics

--8.2.2 Crystallization kinetics

--8.2 Crystallization

-8.3 Phase Separation of glass

--8.3 Phase separation of glass

--8.3 Phase separation of glass

-8.4 Questions for phase transformation

--Questions for phase transformation

-Test for chapter 8

9 Sintering

-9.1 Overview of sintering

--9.1 Overview of sintering

--9.1 Overview of sintering

-9.2 The driving forces and models of sintering

--9.2 The driving forces and models of sintering

--9.2 The driving forces and models of sintering

-9.3 Solid state sintering

--9.3.1 Evaporation-Condensation mass transfer

--9.3.2 Diffusion mass transfer

--9.3 Solid state sintering

-9.4 Liquid phase sintering

--9.4.1 Flow mass transfer

--9.4.2 Solution-Precipitation mass transfer

--9.4 Liquid phase sintering

-9.5 Grain growth and secondary recrystallization

--9.5.1 Grain growth

--9.5.2 Secondary recrystallization

--9.5 Grain growth and secondary recrystallization

-9.6 Factors affecting sintering

--9.6 Factors affecting sintering

--9.6 Factors affecting sintering

-9.7 Questions for sintering

--Questions for sintering

-Homework for chapter 9

-Test for chapter 9

2.3 Calculation of thermal defect concentration笔记与讨论

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