Dielectric Materials for Wireless CommunicationBy
- Mailadil Sebastian
Microwave dielectric materials play a key role in our global society with a wide range of applications, from terrestrial and satellite communication including software radio, GPS, and DBS TV to environmental monitoring via satellite.
A small ceramic component made from a dielectric material is fundamental to the operation of filters and oscillators in several microwave systems. In microwave communications, dielectric resonator filters are used to discriminate between wanted and unwanted signal frequencies in the transmitted and received signal. When the wanted frequency is extracted and detected, it is necessary to maintain a strong signal. For clarity it is also critical that the wanted signal frequencies are not affected by seasonal temperature changes. In order to meet the specifications of current and future systems, improved or new microwave components based on dedicated dielectric materials and new designs are required. The recent progress in microwave telecommunication, satellite broadcasting and intelligent transport systems (ITS) has resulted in an increased demand for Dielectric Resonators (DRs). With the recent revolution in mobile phone and satellite communication systems using microwaves as the propagation media, the research and development in the field of device miniaturization has been a major challenge in contemporary Materials Science. In a mobile phone communication, the message is sent from a phone to the nearest base station, and then on via a series of base stations to the other phone. At the heart of each base station is the combiner/filter unit which has the job of receiving the messages, keeping them separate, amplifying the signals and sending then onto the next base station. For such a microwave circuit to work, part of it needs to resonate at the specific working frequency. The frequency determining component (resonator) used in such a high frequency device must satisfy certain criteria. The three important characteristics required for a dielectric resonator are (a) a high dielectric constant which facilitates miniaturization (b) a high quality factor (Qxf) which improves the signal-to-noise ratio, (c) a low temperature coefficient of the resonant frequency which determines the stability of the transmitted frequency.
During the past 25 years scientists the world over have developed a large number of new materials (about 3000) or improved the properties of known materials. About 5000 papers have been published and more than 1000 patents filed in the area of dielectric resonators and related technologies. This book brings the data and science of these several useful materials together, which will be of immense benefit to researchers and engineers the world over.
The topics covered in the book includes factors affecting the dielectric properties, measurement of dielectric properties, important low loss dielectric material systems such as perovskites, tungsten bronze type materials, materials in BaO-TiO2 system, (Zr,Sn)TiO4, alumina, rutile, AnBn-1O3n type materials, LTCC, ceramic-polymer composites etc. The book also has a data table listing all reported low loss dielectric materials with properties and references arranged in the order of increasing dielectric constant.
Research scientists and engineers working in the area of wireless communication, postgraduate students in physical and chemical sciences, graduate and postgraduate students in electronic engineering.
Hardbound, 688 Pages
Published: June 2008
- Foreword by Prof. Neil Alford, F R Eng. Imperial College LondonChapter 1. IntroductionChapter 2. Measurement of microwave dielectric properties and factors affecting them 2.1. Permittivity2.2. Quality factor (Q)2.3. Measurement of microwave dielectric properties 2.3.1. Hakki and Coleman (Courtney) method 22.214.171.124. Measurement of Permittivity 126.96.36.199. Measurement of loss tangent 2.3.2. TE01Ô) mode dielectric resonator method 2.3.3. Measurement of quality factor by stripline method 2.3.4. Whispering Gallery Mode resonators 2.3.5. Split Post Dielectric Resonator (SPDR) method 2.3.6. Cavity Perturbation method 2.3.7. TM010 mode and Re-entrant cavity method 2.3.8. TE01n mode cavities 2.4. Estimation of dielectric loss by spectroscopic methods2.5. Factors affecting the dielectric loss2.6. Correction for porosity2.7. Calculation of permittivity using Clausius Mossotti equation2.8. Measurement of temperature coefficient of resonant frequency2.9. Tuning of resonant frequency ReferencesChapter 3. Microwave dielectric materials in the BaO-TiO2 system3.1. Introduction3.2. BaTi4O9 3.2.1. Microwave dielectric properties3.3. BaTi5O113.4. Ba2Ti9O20 3.4.1. Preparation 3.4.2. Structure 3.4.3. Properties3.5. BaTi4O9/Ba2Ti9O20 composites3.6. Conclusion References Chapter 4. (Zr,Sn)TiO4 ceramics4.1. Introduction4.2. Preparation 4.2.1. Solid state method 4.2.2. Wet chemical methods4.3. Crystal structure and phase transformation4.4. Microwave dielectric properties4.5. Conclusion ReferencesChapter 5. Tungsten bronze type materials5.1. Introduction5.2. Crystal structure5.3. Preparation of Ba6-3xLn8+2xTi18O54 ceramics5.4. Dielectric properties 5.4.1. Effect of dopants 5.4.2. Substitution for Ba 5.4.3. Substitution for Ti 5.4.4. Texturing 5.4.5. Effect of glass 5.5. Phase transition5.6. Conclusion ReferencesChapter 6. ABO3 type perovskites 6.1. Introduction6.2. Tolerance factor (t) and perovskite cell parameter (ap)6.3. ATiO3 (A=Ba, Sr, Ca) 6.4. Ag(Nb1-xTax)O36.5. Ca(Li1/3Nb2/3)O3-Ô6.6. CaO-Ln2O3-TiO2-Li2O system6.7. LnAlO36.8. Conclusion ReferencesChapter 7. A(B¡¦1/2B¡¨1/2)O3 complex perovskites 7.1. Introduction7.2. Ba(B¡¦1/2Nb1/2)O3 ceramics7.3. Ba(B¡¦1/2Ta1/2)O3 ceramics7.4. Sr(B¡¦1/2Nb1/2)O3 ceramics 7.4.1. Tailoring äf of Sr(B¡¦1/2Nb1/2)O3 ceramics7.5 Sr(B¡¦1/2Ta1/2)O3 ceramics 7.5.1. Effect of non-stoichiometry in Sr(B¡¦1/2Ta1/2)O3 ceramics 7.5.2. Effect of A and B Site substitutions 7.5.3. Effect of rutile addition7.6. Ca(B¡¦1/2Nb1/2)O3 ceramics 7.6.1. Tailoring the dielectric properties of Ca(B¡¦1/2Nb1/2)O3 ceramics by addition of TiO2 and CaTiO3 7.6.2. Effect of A and B site substitutions on the structure and dielectric properties 7.7. Ca(B¡¦1/2Ta1/2)O3 ceramics7.8. (Pb1-xCax)(Fe1/2B¡¨1/2)O3 [B¡¦=Nb,Ta]7.9. Ln(A1/2Ti1/2)O3 [Ln=lanthanide, A=Zn, Mg, Co]7.10 Conclusion ReferencesChapter 8. A(B¡¦1/3B¡¨2/3)O3 complex perovskites 8.1. Introduction8.2. Ba(Zn1/3Ta2/3)O3 (BZT) 8.2.1. Preparation 8.2.2. Crystal structure and ordering 8.2.3. Dielectric properties 8.2.4. Effect of BaZrO3 addition in BZT8.3. Ba(Mg1/3Ta2/3)O3 (BMT) 8.3.1. Preparation 8.3.2 Crystal structure and ordering 8.3.3. Properties 8.3.4 Effect of dopants 8.3.5. effect of glass addition 8.3.6. Nonstoichiometry 8.3.7 Dielectric properties at low temperatures8.4. (Ba,Sr)(Mg1/3Ta2/3)O38.5. Ba(Zn1/3Nb2/3)O3 (BZN) 8.5.1. Preparation 8.5.2. Dielectric properties8.6. Ba(Ni1/3Nb2/3)O38.7. Ba(Co1/2Nb2/3)O38.8. Ba(Mg(Nb1/3Nb2/3)O38.9 Conclusion ReferencesChapter 9. Cation deficient perovskites9.1 Introduction9.2. A4B3O12 ceramics9.3. A5B4O15 ceramics.9.4. A6B5O18 ceramics9.5. A8B7O24 ceramics 9.6. La2/3(Mg1/2W1/2)O3 9.7. Conclusions ReferencesChapter 10. A(A1/4B2/4C1/4)O3 (A=Ca,Mg, Zn, Sr, Co.., B=Nb,Ta) type materials10.1 Introduction10.2. Structure and properties of Ca5B2TiO12 [B=Nb,Ta] ceramics10.3. Effect of dopant addition in Ca5B2TiO12 (B=Nb.Ta) ceramics10.4. Effect of glass addition10.5. Effect of cationic substitution in A and B sites in Ca5B2TiO12 ceramics B=Nb,Ta)10.6 Conclusions ReferencesChapter 11. Alumina, titania and other materials11.1. Alumina11.2. Titania11.3. CeO211.4. Silicates11.5. Spinel11.6. Tungstates11.7. AB2O6(A=Zn,Co, Ni, Sr, Ca, Mg;B=Nb,Ta)11.8. A4M2O9 (M=Mg, Mn, Fe, Co: A=Ta,Nb)11.9. Ln2BaAO5 (Ln= lanthanide); A=Cu, Zn, Mg)11.10. LnTiAO6 (A=Nb.Ta)11.11. MgTiO311.12. ZnO-TiO2 system.11.13. Conclusion ReferencesChapter 12: Low Temperature Cofired Ceramics (LTCC)12.1. Introduction12.2. LTCC process and design aspects of microwave components12.3 Materials selection and requirements12.3. Important characteristics required for the glass ceramic composites 12.3.1 densification 12.3.2 Õr in the range 5-70 12.3.3. Qf>1000 12.3.4 äf close to zero 12.3.5. High thermal conductivity 12.3.6. Thermal expansion 12.3.7. Chemical compatibility with electrode material12.4. Commercial LTCC materials12.5. Glass-ceramic composites12.6. Microwave dielectric properties of glasses 12.7. LTCC materials and their properties 12.7.1 Alumina 12.7.2. TiO2 based LTCC 12.7.3. Li2O-M2O5-TiO2 system 12.7.4. Bismuth based materials 188.8.131.52. BiAO4 (A=Nb.TA) 184.108.40.206 BiO2-TiO2 220.127.116.11. Bi2O3-ZnO-Nb2O5 18.104.22.168. Bi12MO20-Ô 12.7.5 TeO2 type 12.7.6. ZnO-TiO2 system 12.7.7. MgAlO4 and ZnAlO4 12.7.8. Tungsten-bronze type 12.7.9. Pb1-xCax(Fe1/2Nb1/2)O3 12.7.10. Ca(Li1/3Nb2/3)O3)-d 12.7.11. BaO-TiO2 system 12.7.12 Vanadate system 12.7.13. Zinc and barium niobates 12.7.14. (MgCa)TiO3 12.7.15. Mg4(Nb/Ta)2O9 12. 7.16. Ba(Mg1/3Nb2/3)O3 12.7.17. (Zr,Sn)TiO4 12.7.18. Ag(NbTa)O3 system 12.7.19. AMP)2)O7 12.7.20 ABO4 (A=Ca, Sr, Ba, Mg, Mn, Zn; B=Mo,W) 12.8. Conclusion ReferencesChapter 13. Tailoring the properties of low loss dielectrics 13.1 Introduction13.2 Solid solution formation13.3 Use of additives13.4 Non-stoichiometry13.5 Stacked resonators13.6 Tailoring the properties by mixture formationReferencesChapter 14. ConclusionAppendix I. Ionic radii Appendix II. List of DRs reported in the literature with properties and references