氏名　Sirirat Pattanachan
学位の種類　博士（工学）
学位記番号　博甲第284号
学位授与の日付　平成15年12月31日
学位論文題目　Mechanical Behavior of Oxide Ceramic-Based Smart Composites with Piezoelectric Phase　（圧電相を有する酸化物セラミックス基複合知能材料の力学的挙動）
論文審査委員
　主査　教授　武藤　睦治
　副査　教授　古口　日出男
　副査　助教授　岡崎　正和
　副査　助教授　井原　郁夫
　副査　千葉大学工学部　助教授　浅沼　博

• 論文目次
• 論文要旨

［平成15（2003）年度博士論文題名一覧］ ［博士論文題名一覧］に戻る．

CONTENTS

Abstract
contents

Chapter1　INTRODUCTION AND SCOPE OF THIS WORK　p.1
1. Smart materials　p.2
2. Why use a piezoelectric materials as a smart material　p.4
3. Piezoelectric ceramics　p.5
4. Piezoelectricity and basic relationship　p.8
5. Barium Titante　p.12
6. A new sintering method :Spark Plasma Sintering　p.20
7. Toughening nechanism in ceramic composite materials　p.23
8. Literature survey and the related works　p.25
9. Scope of the present works　p.31
References　p.33

Chapter2　MICROSTRUCTURE AND FRACTURE TOUGHNESS OF SPARK PLASMA SINTERED AL2O3 BASED COMPOSITES BaTiO3 PARTICULATES　p.38
1.Introduction　p.39
2.Preparation of composites and sintering process　p.41
3.Results and discussion　p.44
4.Conclusion　p.59
References　p.60

Chapter3　MICRPSTRUCTURE AND FRACTURE TOUGHNESS OF SPARK PLASMA SINTERED Mgo BASED COMPOSITES WITH BaTio3 PARTICULATES　p.62
1.Introduction　p.63
2.Experimental Procedure　p.64
3.Results and discussion　p.65
4.Conclusion　p.74
References　p.74

Chapter4　EFFECT OF POLARIZATION ON FRACTURE TOUGHNESS OF BaTio3 -Al2O3 AND BaTio3-Mgo COMPOSITES　p.77
1.Introduction　p.78
2.Experimental Procedure　p.80
3.Results and discussion　p.84
4.Conclusion　p.97
References　p.97

Chapter5　FRACTURE TOUGHNESS OF BaTio3-Al2O3 COMPOSITES APPLIED ELECTRIC FIELD　p.100
1.Introduction　p.101
2.Experimental Procedure　p.102
3.Results and discussion　p.105
4.Conclusion　p.110
References　p.110

Chapter6　FATIGUE BEHAVIOR OF BaTio3-Al2O3 COMPOSITE　p.113
1.Introduction　p.114
2.Experimental Procedure　p.115
3.Results and discussion　p.120
4.Conclusion　p.128
References　p.129

Chapter7　FABRICATION AND EVALUATION OF PIEZOELECTRIC LAMINATES FOR SMART MATERIALS　p.131
1.Introduction　p.132
2.Experimental Procedure　p.134
3.Results and discussion　p.136
4.Conclusion　p.148
References　p.149

Chapter8 OVERALL CONCLUSIONS AND THE FUTURE PROSPECTS　p.151
1.Overall conclusions　p.152
2.The prospects of future works　p.157

Acknowledge　p.159

Since ceramics are inherently brittle, various approaches have been attempted to improve their mechanical properties. Recently, novel composite materials that exhibit both the excellent structural and functional properties are interested in advanced engineering applications. Many research works on fracture behavior have been done for monolithic piezoelectric materials, while only few works have been conducted for piezoelectric composites. In the present study, ceramic composites, which were reinforced by the ferroelectric/piezoelectric secondary dispersions and piezoelectric laminates as smart materials, were fabricated. Their mechanical behavior and main toughening mechanism were investigated. Eight chapters are included in this thesis.
Chapter 1 "Introduction and scope of this work": related to the present research work were reviewed and the objectives of this study were addressed.
Chapter 2 "Microstructure and fracture toughness of spark plasma sintered Al2O3-based ceramic composite with BaTiO3 piezoelectric phase": dense BaTiO3-Al2O3 composites were fabricated by spark plasma sintering （SPS） at sintering temperatures between 1100 and 1500 C with a heating rate of 100 C/min. Microstructure, phase, density and mechanical properties of the present sintered composites were investigated as a function of BaTiO3 content. High-density of BaTiO3-Al2O3 with various composites could be achieved by SPS at lower sintering temperatures compared to those by pressure-less sintering （PLS） and fracture toughness of the composites was improved, compared to the monolithic Al2O3.
Chapter 3 "Microstructure and fracture toughness of spark plasma sintered MgO-based ceramic composite with BaTiO3 piezoelectric phase": since reaction phases between BaTiO3 and Al2O3 were observed, MgO-based composites were fabricated to avoid the reaction third phase. The higher fracture toughness of BaTiO3-MgO composite with 10 vol% BaTiO3 content was achieved, compared to monolithic MgO. No reaction phase was found for the sintered BaTiO3-MgO composites. With 10 vol% BaTiO3 content, transgranular crack paths at or near BaTiO3 particle were increasingly observed. This toughening effect can be primarily attributed to stress-induced domain switching toughening.
Chapter 4 "Effect of polarization on fracture toughness of BaTiO3-Al2O3 and BaTiO3-MgO composites": an applied electric field induced distinct anisotropy in fracture toughness of this composite between parallel and perpendicular to the poling direction. After polarization, fracture toughnesses of BaTiO3-Al2O3 and BaTiO3-MgO composites parallel to the poling direction were improved and higher than those before polarization. Anisotropy in residual stress was observed after polarization. The anisotropy in crack propagation behavior could be explained not by the residual stress presented in the poled BaTiO3-Al2O3 composites, but by the domain switching mechanism.
Chapter 5 "Fracture toughnesses of BaTiO3 and BaTiO3-Al2O3 under applied electric field": to discuss the toughening mechanisms, in this chapter, fracture toughnesses of 5 mol%BaTiO3-Al2O3 composite （denoted as 95A5B） for both before and after polarization were investigated under various applied electric field. Applied electric fields could increase or decrease fracture toughness of 95A5B composite depending on the direction of electric field. Polarization switching of piezoelectric BaTiO3 phase under electric fields has a significant influence on fracture toughness of the present composite.
Chapter 6 "Fatigue behavior of BaTiO3-Al2O3 composite": Fatigue tests of poled and unpoled 95A5B were conducted under sinusoidal waveform with frequency of 20 Hz at load ratio of 0.1. From the S-N curve, the present composites also exhibited high fatigue resistance compared to monolithic Al2O3. From the fatigue crack growth tests, poled BaTiO3-Al2O3 indicated high crack growth resistance compared to unpoled one and monolithic Al2O3 in the low crack growth rate region. From the detailed observations, the improvement of fatigue strength and crack growth resistance are seemed to be mainly due to stress-induced domain switching.
Chapter 7 "Fabrication and evaluation of piezoelectric laminates for smart material": piezoelectric laminates, BaTiO3/MgO （pre-shaped）/BaTiO3 and BaTiO3/10 vol% BaTiO3-MgO/BaTiO3, were successfully fabricated by using SPS method. Fatigue test was conducted to investigate the relationship between the crack length and the response output signal of the poled laminates. With increasing the maximum stress, the response output range of poled BaTiO3 monotonically increased. The decreasing of the response output range was agreement with increasing of the crack length. This suggests that the present laminates have a sensing function of crack and can be considered as a smart material.
Chapter 8 "Overall conclusion and future prospects": the general conclusions and future prospects have been given.