電子セラミックスと固体化学 Electroceramics and Solid State Cheminstry

1. 電子セラミックスと固体化学Electroceramics and Solid State Cheminstry 格子欠陥の利用 Application of Lattice Defects 工学部　応用化学科　片山　恵一

2. 電子セラミックスとは？What is Electroceramics?　 固体化学とは？ What is Solid State Chemistry?　　　　 Today's subjects これらの関係は？ What is the relationship between these two subjects ?　 この関係は何に利用されている？ What has thisrelationship been utilized for?　 The interdisciplinary study of these two subjects has developed technology, and has been producing lots of sophisticated products underpinned modern society.

3. 講義の流れFlow of today's talk • 電子セラミックスとは？ • What is Electroceramics? • 固体化学 • Solid State Chemistry • 実用例 • Application

4. 電子セラミックスとは？What is Electroceramics?

5. セラミックスとは？What isa ceramic? 加熱して作製される非金属無機固体化合物 A ceramic is an inorganic, non-metallic solid prepared by heating. 　　　例：陶磁器pottery 　　　　　半導体材料として広範に利用されている。 In the 20th century, new ceramic materials were developed for use in advanced ceramic engineering; for example, in semiconductors.

6. Definition of Ceramicsセラミックスの定義 The term ‘ceramics’ is restricted to polycrystalline, inorganic, non-metallic materials that can acquire their mechanical strength through a firing or sintering process. Glass and single crystals are sometimes included as a matter of convenience.　　　　　　　　　　 厳密には多結晶を対象とするが、単結晶･ガラスを含む場合もある

7. 電子セラミックスClassification of Electroceramics • Insulators (絶縁体 )　　基板、点火プラグ • Magnetics (磁性体 )　　磁石、記録装置 • Dielectrics (誘電体 )　　ｺﾝﾃﾞﾝｻ、メモリー • Conductors (導電体 )　　抵抗、ｻｰﾐｽﾀ、発熱体、ｶﾞｽｾﾝｻ • Piezoelectrics (圧電体 )　ｽﾋﾟｰｶ、ﾌｨﾙﾀ、超音波診断装置 • Pyroelectrics (焦電体 )　　赤外線ｾﾝｻ • Optics (光学材料 )　　光ﾌｧｲﾊﾞｰ、透明電極 　　　　　　　　　・　　　 　　　　　　　　　・　　　 　　　　　　　　　・　　　

8. 固体化学の基礎Fundamental Solid State Chemistry

9. Preparative methods Crystal chemistry Phase diagrams Phase transition Electrical properties Magnetic properties Optical properties • • • 固体化学って何？What is Solid State Chemistry? Electroceramics Crystal defects Non-stoichiometry Solid solution

10. Crystal defects Point Defects • Schottky defect • Frenkel defect • intrinsic and extrinsic defects • Interchanged Atoms

11. Perfect and Imperfect Crystals • Perfect Crystalsin which all atoms are at rest on their correct lattice positions. • Imperfect Crystals which contain random defects, resulting in the deficiency of one element. At all real temperatures, crystals are imperfect.

12. Stoichiometry and Non-stoichiometry • Stoichiometric compounds （化学量論組成化合物） • Non-stoichiometric compounds （非化学量論組成化合物）

13. Example of Non-stoichiometric compounds Ferrous oxide: FeO（酸化鉄(Ⅰ)） Ideal formula : FeO 　　Actual formula : Fe1-XO(X≈0.05) In the latter formula, Fe3+ ions are present and O2− vacancies are formed.

14. Why non-stoichiometry exists? Since the solid needs to be overallelectrically neutral, the missing atom's charge needs to be compensated by a change in the charge for another atom in the solid, by changing the oxidation state, or by replacing it with an atom of a different element with a different charge.

15. Types of Defect • Schottky defect（ショットキー欠陥）: A pair of vacant sites, a cation defect and an anion defect　（一対の陽イオンと陰イオンが抜ける） • Frenkel defect（フレンケル欠陥） : An atom displaced off its lattice site into an interstitial site 　（片方のイオンが格子間位置に移動） These defects are described using the Kroger-Vink notation.

16. Cl Cl Na Na Cl Cl Cl Cl Cl Cl Cl Cl Na Na Na Na Na Na Cl Cl Cl Cl Cl Cl Na Na Na Na Cl Cl Na Na Na Na Na Na Na Na Cl Cl Cl Cl Cl Cl Cl Cl Na Na Na Na Na Cl Cl Na Na Na Na Na Na Na Cl Cl Cl Cl Cl Cl Na Na Cl Cl Cl Cl Cl Cl Na Na Cl Cl Cl Cl Na Na Na Na Na Na Na Na Cl Cl Na Na Cl Cl Cl Cl Na Na Na Na Cl Cl Na Na Na Na Na Na Cl Cl Na Na Na Na Cl Cl Cl Cl Cl Cl Cl Cl Na Na Na Na Cl Na Na Cl Cl Cl Cl Cl Cl Cl Na Na Na Na Types of Defect • Schottky defect At room temperature, only one in 1015 of both ion sites in NaCl is vacant.

17. Ag Ag Ag Ag Ag Ag Cl Cl Ag Ag Cl Cl Cl Cl Ag Ag Ag Ag Ag Ag Cl Cl Cl Cl Cl Cl Cl Cl Ag Ag Ag Ag Ag Ag Ag C Cl Cl Cl Cl Cl Ag Ag Ag Ag Ag Ag Cl Cl Cl Cl Cl Cl Cl Cl Ag Ag Ag Ag Ag Ag Ag Ag Cl Cl Cl Cl Cl Cl Types of Defect • Frenkel defect

18. Kroger-Vink notationクレーガー･ビンク記号 • The symbol for the atom involved, or “V” if the site is vacant　　（空孔はVで表す） • A superscript indicating the net charge: “” for charge 1, “” for zero net charge, 　 “ ” for charge 1　　　　　（元に比べて“＋”の場合“” 、”－“の場合は“” 、変化なしの場合は“” ） • A subscript to indicated the nature of the site in an ideal crystal, with ” i” for an interstitial site and “s” for a surface site　（格子間位置は”i” )

19. Kroger-Vink notation Na Cl Na , Cl : Na+and Cl ions on regular lattice sites, zero net charge V : a Na+ ion vacancy, net charge 1 V : a Cl ion vacancy, net charge 1 Mg : a substitutional Mg2+ ion on a Na site, charge +1 Ag  : an interstitial Ag+ ion in AgCl, charge 1 F  : an interstitial F ion in CaF2, charge 1 Na Cl Na i i

20. Examples of Kroger-Vink notation • NaCl null → VNa’+VCl• 無　　　　空のNa+格子点　　　空のCl–格子点 (NaxNa+ClxCl→ VNa’+VCl• +Naxs +Clxs ) • AgCl AgAgx → Ag•i + VAg’ 　　　空のAg+格子点　　　　　　　　　　　 　　　 格子間位置にあるAg+ 本来の格子点にあるAg+ (AgxAg+ClxCl→ Agi•+V’Ag+ClxCl)

21. Other examples of Defects • Intrinsic defects:defects which are thermally created Example: ZnO(Zn1+xO), NiO(Ni1-xO) • Extrinsic defects:defects which are associated with dopants or impurities Example 1: Al2O3 includingCr2O3 Example 2: ZnO including Al2O3

22. Solid Solutions（固溶体） • A crystalline phase that can have variable composition　　　　　　　　　　 (規則性なく組成が変化する結晶相） 水とエタノールの混合と同じ！ Examples • Fe0.95O : Mixtures of FeO and Fe2O3 Problem 1: Calculate the molar fraction of each compounds in Fe0.95O.

23. Answer to the problem The formation of Fe0.95O is; x FeO + y Fe2O3→Fe0.95O (x: mols of FeO in SS, y: mols of Fe2O3 in SS) x+2y=0.95 ·····(1) x+3y=1.00 ·····(2) (2) – (1); y=0.05, x=0.85 Answer: FeO = 0.85 / 0.90 = 94.4 mol% Fe2O3= 100 – 94.4 = 5.6 mol%

24. Types of Solid Solutions • Substitutional solid solutions (置換型) • The atoms or ions that is being introduced directly replaces an atom or ion in the parent structure • Interstitial solid solutions （格子間型） • The introduced species occupies a site that is normally empty and no ions or atoms are left out

25. Substitutional solid solutions • Al2-xCrxO3 (0≤x ≤ 2) (derived from Al2O3) • Al3+ and Cr3+ ions are distributed at random • the probability that it is one or the other is related to the composition x. (each site is occupied by an ‘average cation’) • Average cation whose properties, atomic number, size, etc., are intermediate between those of Al3+ and Cr3+ ions 　(固溶体の物性値は、それぞれの値の平均！) Example Ionic radius of a cation in Al1.6Cr0.4O3 is calculated to be 69.1 nm from ionic radii of Al3+: 67.5 nm and Cr3+: 75.5 nm.

26. Interstitial solid solutions • If the solute atoms are small, they may dissolve interstitially in the host crystal. • YF3 in CaF2 • Y3+ is interstitially located in the lattice, and V•Ca is created. • PdHx(0 ≤ x ≤ 0.7) • Pd metal occludes(吸蔵する)H2 gas, and H atoms occupy interstitial sites.

27. 応用例1：BaTiO3系サーミスタPTC thernistor

28. 6 5 NTCThermistor 4 log(ρ/Ω m) 3 2 PTC Thermistor 1 Pt wire 0 0 40 80 120 160 T/ºC Temperature-sensitive Resistors(Thermal Resistors :Thermistors) • Negative temperature coefficient of resistance (NTC) • Positive temperature coefficient of resistance (PTC)

29. 6 5 NTCThermistor 4 log(ρ/Ω m) 3 2 PTC Thermistor 1 Pt wire 0 0 40 80 120 160 T/ºC Transformation of BaTiO3 相変態 単斜晶 立方晶 菱面体晶 正方晶

30. PTC Thermistors • Lanthanum-doped BaTiO3(Ba1-XLaXTiO3) or • Niobium-doped BaTiO3 (BaTi1-XNbXO3)

31. Defect chemistry of BaTiO3 • In case of addition of La2O3 and forming non-stoichiometric BaTiO3 • BaO is formed or vacancies of Ti are formed. 　　 La2O3→ 2La•Ba+ 2BaO +2e’ + 1/2O2 La2O3→ 2La•Ba+ 2V••••Ti + 10e’ + 1/2O2 • In case of addition of La2O3 and forming stoichiometric BaTiO3 • La2O3(+2TiO2) La2O3→ 2La•Ba+ 2OXO +2e’ + 1/2O2 • La•Ba is compensated by an electron ( 2TiO2 + 2BaO → 2BaXBa + 2TiXTi + 6OXO ).

32. Defect chemistry of BaTiO3 • In case of another stoichiometric BaTiO3 • Nb2O5(+2BaO) Nb2O5→ 2Nb•Ti+ 4OXO +2e’ + 1/2O2 • In case of stoichiometric BaTiO3 • Al2O3(+2TiO2) • Al2O3→ 2Al’Ti+ 3OXO +V••O • or Al2O3+ 1/2O2+2e-→ 2Al’Ti+ 4OXO

33. Electroceramics 電子セラミックス Solid state chemistry 固体化学

34. Electroceramics and Solid State Cheminstry電子セラミックスと固体化学 The End Application of Lattice Defects 格子欠陥の利用 工学部　応用化学科　片山　恵一

35. Assignment Explain the relationship 　　　between electroceramics and crystal defects 　within 200 words or less. 　　　　　　　　　（日本語の場合は500字以内） Submission deadline: Feb. 27 E-mail to: Katayama Keiichi<katakei@keyaki.cc.u-tokai.ac.jp>