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

Today's subjects電子セラミックスと

は？ What is Electroceramics?

固体化学とは？What is

Solid State Chemistry?

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 this relationship been utilized for? The interdisciplinary study of these two subjects has developed technology, and has been producing lots of sophisticated products underpinned modern society.

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

電子セラミックスとは？What is Electroceramics?

セラミックスとは？What is a 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.

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

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 ) 　　 、メモリーｺﾝﾃﾞﾝｻ• Conductors ( 導電体 ) 　　抵抗、 、発熱体、ｻｰﾐｽﾀ ｶﾞｽｾﾝｻ• Piezoelectrics ( 圧電体 ) 　 、 、超音波診断装置ｽﾋﾟｰｶ ﾌｨﾙﾀ• Pyroelectrics ( 焦電体 ) 　　赤外線ｾﾝｻ• Optics ( 光学材料 ) 　　光 、透明電極ﾌｧｲﾊﾞｰ　　　　　　　　　・　　　　　　　　　　　　・　　　　　　　　　　　　・　　　

固体化学の基礎Fundamental

Solid State Chemistry

固体化学って何？What is Solid State Chemistry?

• Preparative methods• Crystal chemistry• Phase diagrams• Phase transition• Electrical properties• Magnetic properties• Optical properties

•

•

•

Crystal defectsNon-stoichiometrySolid solution

Electroceramics

Crystal defects

Point Defects Schottky defect Frenkel defect intrinsic and extrinsic defects Interchanged Atoms

Perfect and Imperfect Crystals

• Perfect Crystals in 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.

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）

Example of Non-stoichiometric compounds

Ideal formula : FeO Actual formula : Fe1-XO (X≈0.05)

In the latter formula, Fe3+ ions are present

and O2− vacancies are formed.

Ferrous oxide: FeO （酸化鉄(Ⅰ) ）

Why non-stoichiometry exists?

Since the solid needs to be overall electrically 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.

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.

Types of Defect

• Schottky defect

At room temperature, only one in 1015 of both ion sites in NaCl is vacant.

NaNa NaNa Na

Na Na Na Na

Na NaNaNaNa

Na Na Na Na

Na NaNaNa

Na

Na Na Na Na

Na Na NaNa

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl Na Na Na Na

NaNa NaNa Na

Na Na Na Na

Na NaNaNaNa

Na Na Na Na

Na NaNaNa

Na

Na Na Na Na

Na Na NaNa

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl Na Na Na Na

Types of Defect

• Frenkel defect

Ag

Ag

Ag Ag Ag Ag

Ag Ag Ag

Ag Ag

Ag Ag Ag

Ag

AgAg

ClClCl

Cl

Cl

Cl

Cl

Cl Cl Cl

Cl Cl

Cl Cl Cl

Cl Cl

Ag

Ag

Ag Ag Ag Ag

Ag Ag Ag

Ag Ag

Ag Ag Ag

Ag

AgAg

Ag

ClClCl

Cl

Cl

Cl

Cl

Cl Cl Cl

C Cl

Cl Cl Cl

Cl Cl

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” )

Kroger-Vink notation

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

ii

Na

Cl

Na

Na Cl

Examples of Kroger-Vink notation• NaCl

null → VNa’+VCl•

無　　　　空の Na+ 格子点　　　空の Cl– 格子点

(NaxNa+Clx

Cl→ VNa’+VCl• +Nax

s +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+Clx

Cl→ Agi•+V’Ag+Clx

Cl)

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 including Cr2O3

Example 2: ZnO including Al2O3

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.

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%

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

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.

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.

応用例 1 ： BaTiO3 系サーミスタ PTC thernistor

Temperature-sensitive Resistors(Thermal Resistors :Thermistors)

• Negative temperature coefficient of resistance (NTC)

• Positive temperature coefficient of resistance (PTC)

0 40 80 120 1600

1

2

3

4

5

6

log(

ρ/Ω

m)

T/ºC

PTC Thermistor

Pt wire

NTC Thermistor

Transformation of BaTiO3

0 40 80 120 1600

1

2

3

4

5

6

log(

ρ/Ω

m)

T/ºC

PTC Thermistor

Pt wire

NTC Thermistor

相変態

立方晶

正方晶

単斜晶

菱面体晶

PTC Thermistors

• Lanthanum-doped BaTiO3(Ba1-XLaXTiO3)

or

• Niobium-doped BaTiO3 (BaTi1-XNbXO3)

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 + 2OX

O +2e’ + 1/2O2

• La•Ba is compensated by an electron ( 2TiO2 + 2BaO →

2BaXBa + 2TiX

Ti + 6OXO ).

Defect chemistry of BaTiO3

• In case of another stoichiometric BaTiO3

Nb2O5(+2BaO)

Nb2O5 → 2Nb•Ti + 4OX

O +2e’ + 1/2O2

• In case of stoichiometric BaTiO3

–Al2O3(+2TiO2)

Al2O3 → 2Al’Ti + 3OXO +V••

O

or Al2O3 + 1/2O2 +2e- → 2Al’Ti + 4OXO

Solid state chemistry固体化学

Solid state chemistry固体化学

Electroceramics電子セラミックスElectroceramics電子セラミックス

The End

Electroceramics and Solid State Cheminstry

電子セラミックスと固体化学

Application of Lattice Defects

格子欠陥の利用

工学部　応用化学科　片山　恵一

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>