Wunderlich W. (ed.). Ceramic Materials

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Ceramic Materials

edited by

Wilfried Wunderlich

SCIYO

Ceramic Materials

Edited by Wilfried Wunderlich

Published by Sciyo

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Ceramic Materials, Edited by Wilfried Wunderlich

p. cm.

ISBN 978-953-307-145-9

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Chapter 1

Chapter 2

Chapter 3

Chapter 4

Chapter 5

Chapter 6

Chapter 7

Chapter 8

Chapter 9

Preface VII

Development of Thermoelectric materials based on

NaTaO3 - composite ceramics 1

Wilfried Wunderlich and Bernd Baufeld

Glass-Ceramics Containing Nano-Crystallites of Oxide

Semiconductor 29

Hirokazu Masai, Yoshihiro Takahashi and Takumi Fujiwara

Tape Casting Ceramics for high temperature

Fuel Cell applications 49

Alain S.Thorel

Alkoxide Molecular Precursors for Nanomaterials:

A One Step Strategy for Oxide Ceramics 69

Łukasz John and Piotr Sobota

New ceramic microﬁltration membranes from Tunisian natural

materials: Application for the cuttleﬁsh efﬂuents treatment 87

Sabeur Khemakhem, André Larbot, Raja Ben Amar

Electron microscopy and microanalysis of the ﬁber, matrix and ﬁber/

matrix interface in sic based ceramic composite material for use in a

fusion reactor application 99

Tea Toplisek, Goran Drazic, Vilibald Bukosek, Sasa Novak and Spomenka Kobe

Mechanical Properties of Ceramics by Indentation:

Principle and Applications 115

Didier Chicot and Arnaud Tricoteaux

Ceramic Materials and Color in Dentistry 155

Cláudia Ângela Maziero Volpato, Márcio Celso Fredel Analúcia Gebler Philippi

and Carlos Otávio Petter

Surface quality controls mechanical strength and fatigue

lifetime of dental ceramics and resin composites 175

Ulrich Lohbauer, Roland Frankenberger and Norbert Krämer

Contents

Chapter 10

Chapter 11

Re-use of ceramic wastes in construction 197

Andrés Juan, César Medina, M. Ignacio Guerra, Julia M. Morán,

Pedro J. Aguado, M. Isabel Sánchez de Rojas, Moisés Frías and Olga Rodríguez

Ceramic Products from Waste 215

André Zimmer

“Ceramic materials” is the title of this book, which describes the state-of-the-art of some

aspects in this large eld in engineering materials. By invitation of the publisher, several

authors from ten countries, most of them do not know each other, have collected a bunch

of chapters which cover a wide area of engineering science. The rst three chapters describe

the fundamental aspects of functional ceramics for thermoelectric, semiconductor and fuel

cell applications. Chapters 4, 5 and 6 describe the processing of nano-ceramics and their

characterisation. The following chapters describe structural ceramics; chapter 7 describes a

new hardness characterisation method for thin lms, and chapters 8 and 9 describe ceramic

materials for dental applications. Finally, chapters 10 and 11 describe the re-use of ceramics

for new structural applications.

This is the rst book of a series of forthcoming publications on this eld by Sciyo publisher.

The reader can enjoy both a classical printed version on demand for a small charge, as well as

the online version free for download. Your citation decides about the acceptance, distribution,

and impact of this piece of knowledge. Please enjoy reading and may this book help promote

the progress in ceramic development for better life on earth.

Editor

Prof.Dr. Wilfried Wunderlich

Tokai University, Dept. Mat.Sci.,

Japan

Preface

Development of Thermoelectric materials based on NaTaO3 - composite ceramics 1

Development of Thermoelectric materials based on NaTaO3 - composite

ceramics

Wilfried Wunderlich and Bernd Baufeld

Development of Thermoelectric materials

based on NaTaO

- composite ceramics

Wilfried Wunderlich

and Bernd Baufeld

Tokai University, Dept. Material Science., Kitakaname 1117, Hiratsuka-shi, Japan

Kath. Universiteit Leuven, Dpt MTM Metallurgy and Ma. Eng., Leuven, Belgium

1. Introduction

This chapter describes the development of novel thermoelectric materials for high-

temperature applications like gas burners, combustion engines, nuclear fuel, or furnaces.

The goal of this development is to recycle waste heat for energy harvesting in order to

contribute in saving the environment. The research results are described in the following

sub-chapters in four different sections.

After a general review about perovskites and NaTaO

in section 2, ab-initio-simulations of

the Seebeck coefficient are described in section 3. The Seebeck coefficient strongly depends

on the effective mass and carrier concentration. The electronic band-structure calculations

showed a large electron effective mass for NaTaO

. Heavily doping changes NaTaO

’s band-

structure in a similar way as the well-known thermoelectric material Nb-doped SrTiO

Hence, NaTaO

, which is stable up 2083 K and which is known as a material with excellent

photo-catalytic properties, was chosen as a candidate for thermoelectric materials.

Section 4 describes the finding of suitable doping elements by sintering NaTaO

with

different raw materials. While both, pure NaTaO

and NaTaO

sintered with Fe

, are

almost insulators, it was discovered that sintering with metallic iron increases both, electric

conductivity and Seebeck coefficient. Microstructural characterization by SEM and XRD

measurements showed that a NaTaO

-Fe

composite material is formed. The amount of

Fe solved in the NaTaO

lattice is much higher when the starting materials consist of Fe

instead of Fe

. Addition of several metals like Mn, Cr, Ti, Ni, Cu, Mo, W, Fe, and Ag were

tested, but only the later two elements lead to remarkable electric conductivity observed

above 773 K.

Section 5 describes the measurement of thermoelectric properties such as Seebeck-voltage at

a large temperature gradient, a method which is close to applications, but not yet commonly

used, because the thermoelectric theory is based on small temperature gradients. Thermal

conductivity is not measured, but only estimated. The doping is achieved by sintering

metallic iron or silver together with NaTaO

. The results are high negative Seebeck voltages

up to -320 mV at a temperature difference of 700 K, as well as high closed-circuit currents up

to -250 A for Fe-doping and positive values for Ag-doping. Besides reporting previous

results, several new findings are described here for the first time. Composites with Cu yield

Ceramic Materials 2

to a small Seebeck voltage of about -10 mV with a strong response, when heat flow direction

is reversed.

In section 6 the thermokinetic measurement by differential scanning calorimetry (DSC) and

thermoanalysis (TA) clarifies the reaction sintering between Fe and NaTaO

. The

experimental data obtained at different heating rates were analyzed by Friedman analysis

and showed a characteristic shape in the plot of energy versus partial area. Further

directions of improvement, like improving the densification by sintering, are mentioned in

the last section under discussions.

2. Perovskite structure

2.1 Functional Engineering Materials based on Perovskite Crystal structure

The goal of this book chapter is to describe the development of new thermoelectric materials

(TE), whose most important features are described first. Then the perovskite structure is

reviewed, before focusing on the main topic, NaTaO

Successful thermoelectrics have to be semiconductors [Sommerlate et al. 2007, Nolas et al.

2001, Ryan&Fleur 2002, Bulusu et al.2008], so there are two possible approaches in TE

development, one from the ceramic side, which have large Seebeck coefficients, and one

from the metal side, which have large electric conductivity, but a rather poor Seebeck

coefficient. The main goal of development for ceramics, which are the focus in this book, is

the improvement of the electric conductivity. The engineering targets of such TE-ceramics

are applications in any combustion engines, gas turbines, power plants including nuclear

power plants, furnaces, heaters, burners or in combination with solar cells or solar heaters as

illustrated in fig. 1.

Fig. 1. Possible applications for high-temperature thermoelectric ceramics (in blue color) in

solar cells, solar heaters, combustion engines or gas turbines.

The service temperatures of such devices are usually too high as to be applicable for other

TE materials. The temperature difference [Ryan& Fleur 2002] between the hot chamber

inside and the (cold) ambient environment is considered as the energy source for these

energy conversion devices, which have a long life time and low maintenance costs, because

there are no rotating parts. The main advantage is that any waste heat can be converted into

electricity. Hence, advanced thermoelectrics are both, environment-friendly eco-materials

and energy materials, which main purpose is producing energy. For a wide range of

applications, materials with higher energy conversion efficiency than present TEs need to be

found, in order to be considered as clean energy sources helping to solve the severe CO

problem. One important indicator for efficient thermoelectric material is the figure-of-merit

ZT=S







(1)

which should have a value significantly larger than 1 to be economically reasonable.

Improvement of ZT requires a high Seebeck coefficient S and electric conductivity  and a

low thermal conductivity



. For increasing ZT several concepts for materials design of

thermoelectrics have been introduced [Nolas et al. 2001, Ryan&Fleur 2002, Bulusu et al.2008,

Wunderlich et al. 2009-c]. These are phonon-glass electron-crystal (PGEC) [Terasaki et

al.1997], heavy rattling atoms as phonon absorbers, proper carrier concentration [Vining

1991, Wunderlich et al.2006], differential temperature dependence of density of states, high

density of states at the Fermi energy, high effective electron mass [Wunderlich et al. 2009-a],

superlattice structures with their confined two-dimensional electron gas [Bulusu et al. 2008,

Ohta et al. 2007, Vashaee & Shakouri 2004], and electron-phonon coupling [Sjakste et al.

2007]. As all these factors can influence also the material focused in this chapter NaTaO

, at

first basic principles of the Pervoskite crystal structure are briefly reviewed, as this

interdisciplinary approach is supposed to gain important understanding for future

improvement.

The interest on Perovskite structure related materials has dramatically increased in the past

three decades after the discovery of many superior solid-state properties, which makes

Perovskite materials or their layered derivatives record holders in many fields of solid state

physics as shown in fig. 2. The most popular finding was the discovery of superconductivity

in Y

7-x

(YBCO) for which the Nobel Prize 1987 was provided. The present record

holder is Bi2212 with a critical temperature of T

=120K. A large scale application of YBCO

since 1998 is the linear motor train using the magnetic levitation (Maglev) in Yamanashi-ken

Japan, whose entire rail consists of Helium-cooled superconductors. Present portable phone

technology is all based on layered (Ba,Sr)TiO

dielectric material [Ohsato 2001, Wunderlich

et al. 2000] due to their high dielectric constant (e>10000) and quality factor. During the

materials development detailed spectroscopic data of the electromagnetic resonance [Bobnar

et al. 2002, Lichtenberg et al. 2001] have been measured, which further analysis can provide

more understanding of electron-phonon interactions as one of the key issue for

thermoelectrics based on perovskites. Piezoelectric materials on Pb(Ti

1-x

(PZT) or the

environmental benign lead free K

0.5

NbO

(KNN) materials [Stegk et al. 2009] have an

increasing application demand in actuators and sensors.

Fig. 2. As Perovskite-structure based mate-rials are record holders in many solid-state

properties, they might become so in thermoelectrics too.