清华大学：《材料科学基础》课程教学资源（PPT课件讲稿）Chapter 3. 6 Intermetal l ic Compounds

33.6 Intermetal l ic Compounds (Intermetal l ic Phases) I Future 1. The structure of amb differs from those of either a or b 2. Its composition is variable to more or less extension 3. Mixed bonding 4. Intermediate properties

§3.6 Intermetallic Compounds (Intermetallic Phases) ◆ Ⅰ. Future 1. The structure of AmBn differs from those of either A or B 2. Its composition is variable to more or less extension 3. Mixed bonding 4. Intermediate properties

I Format ion A-B The property of Am Bn is between that of A and B

◆ Ⅱ. Formation A→←B The property of AmBn is between that of A and B

lll. Factor governing the structure of compounds 1)Electrochemical factor (X 2) Electron concentration(e/a) 3)Size factor Metal Nonmetal metalloid

◆ Ⅲ. Factor governing the structure of “compounds”. 1) Electrochemical factor (X) 2) Electron concentration (e/a) 3) Size factor Metal Nonmetal Metalloid

33.7 Normal Valence Compounds I Definition If the number of valence electrons of the cation is suficient to complete octahedron of the anion, the compound is called the normal valence compounds EXample: CmA mec=n(8 -) sometimes: m(ec-ecc-n(8-eaeAA)

§3.7 Normal Valence Compounds Ⅰ. Definition: If the number of valence electrons of the cation is sufficient to complete octahedron of the anion, the compound is called the normal valence compounds. Example: CmAn meC＝n(8－eA) sometimes: m(eC－eCC)＝n(8－eA－eAA)

Classification according to structure 1. NaCl and CaF2 types Nacl (Mg Ca Sr Ba)(se Te (Mn Pb Sn)(Se Te CaF? PtSn, PtIn, pt,P Anti-caF Mg,(si Ge Sn Pb) CuSe LiRAIN LiMgn as Sb Bi) AgMgAs

◆ Ⅱ. Classification according to structure 1. NaCl and CaF2 types NaCl: (Mg Ca Sr Ba)(Se Te) (Mn Pb Sn)(Se Te) CaF2: PtSn2 PtIn2 Pt2P Anti-CaF2: Mg2(Si Ge Sn Pb) Cu2Se Li3AlN2 LiMg(N As Sb Bi) AgMgAs

2. Diamond, Zinc blende, Wurtzite types Zinc blende (Be Zn Ca Hg)(s Se Te 1 Ga In)(P As sb Wurtzite (Zn Cd Mn) (Cd Mn)Se

2. Diamond, Zinc blende, Wurtzite types Zinc blende: (Be Zn Ca Hg)(S Se Te) (Al Ga In)(P As Sb) Wurtzite: (Zn Cd Mn)S (Cd Mn)Se

3. NIAs structure Example (Cr Fe Co Ni)(S Se Sb (Fe Co)Te (Mn Fe Ni Pt Cn)Sn Ni (As Sb Bi)

3. NiAs structure Example: (Cr Fe Co Ni)(S Se Sb) (Fe Co)Te (Mn Fe Ni Pt Cn)Sn Ni(As Sb Bi)

Structure Normal state Ni: As=1: 1

Structure c 4 1 c 4 3 • Normal state —— Ni : As = 1 : 1

When Ni does not full fill octahedral interspaces NI As1

• When Ni does not full fill octahedral interspaces Ni : As 1 : 1

4 Electron phase (Electron compounds For Alloys of IB or transition metals, and B group metals phases with sane or similar structure occur at approximately some electron concentration(ela) these alloys are therefore called as electron compounds

4. Electron Phase (Electron compounds) For Alloys of IB or transition metals, and B group metals phases with sane or similar structure occur at approximately some electron concentration(e/a) these alloys are therefore called as electron compounds