Microwave versus conventional sintering: A review of fundamentals, advantages and applications

Chemistry: From Fundamentals to Manufacturing Helen J. Kitchen,† Simon R. Vallance,†,‡ Jennifer L. Kennedy,†,§ Nuria Tapia-Ruiz,† Lucia Carassiti,† Andrew Harrison, A. Gavin Whittaker, Timothy D. Drysdale, Samuel W. Kingman,‡ and Duncan H. Gregory*,† †WestCHEM, School of Chemistry, University of Glasgow, Joseph Black Building, Glasgow G12 8QQ, United Kingdom ‡Department of Chemical and Environmental Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom School of Engineering, University of Glasgow, James Watt South Building, Glasgow G12 8QQ, United Kingdom Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, F 38042, Grenoble, Cedex 9, France Tan Delta Microwaves Limited, 7 Nettlingflat, Heriot EH38 5YF, United Kingdom

Modern microwave methods in solid-state inorganic materials chemistry: from fundamentals to manufacturing.

A power transfer system is provided. The power transfer system includes a field-focusing element including a dielectric material. The dielectric material includes a ceramic material and a polymer material. The ceramic material includes an oxide compound comprising titanium and the polymer material includes a resin. Further, a method of forming a power transfer system is presented. The method includes forming a resonator. Forming a resonator includes the steps of disposing a metallic layer (62), blending a ceramic material and polymer material to form a dielectric material (64), depositing the dielectric material (64) over the metallic layer (62) to form a dielectric layer, forming a Swiss-roll structure (56) of metallic layer and dielectric layer (64), and curing the Swiss-roll structure (56) to form a monolithic Swiss-roll structure (56).

Dielectric materials for power transfer system

A series of compounds in the Li2O–Bi2O3–MoO3 ternary system were investigated with regard to the preparation, phase composition, microwave dielectric properties, and chemical compatibility with silver (Ag) and aluminum (Al) electrodes. All the ceramics in this work have sintering temperatures lower than 750°C. The sintering behaviors and microwave dielectric properties of three single phases Li2MoO4, (Li0.5Bi0.5)MoO4, and Li8Bi2Mo7O28 bulk ceramics, were of particular focus in this investigation. The Li2MoO4 ceramic can be sintered to a high density at 540°C/2 h with a relative permittivity ∼5.5, a Q×f value of 46 000 GHz, and a temperature coefficient of resonant frequency (TCF) of ∼−160 ppm/°C. The (Li0.5Bi0.5)MoO4 ceramic has a scheelite structure and the largest relative permittivity of 44.4 among the ceramics studied in this work with a sintering temperature around 560°C, a Q×f value of 3200 GHz, and a large positive TCF of ∼+245 ppm/°C. The Li8Bi2Mo7O28 ceramic could be sintered at 540°C and has a relative permittivity of 13.6, a Q×f value of 8000 GHz, and a small negative TCF value of ∼−59 ppm/°C. From the X-ray diffraction analysis of cofired ceramics, the Li2MoO4 ceramic does not react with either Ag or Al powders. The Li8Bi2Mo7O28 ceramic reacts with Ag but not with Al at its densification temperature. The (Li0.5Bi0.5)MoO4 ceramic was found to strongly react with Ag powder and to a limited extent with Al powders. From this study, the Li2O–Bi2O3–MoO3 ternary system has a number of attractive new materials with low sintering temperatures, high-performing microwave dielectric properties, chemical compatibility with both Ag and Al metal electrodes, nontoxicity, and low-cost constituents. All these materials can be included in the new field of ultra-low-temperature cofiring dielectrics for multilayer applications.

Microwave Dielectric Ceramics in Li2O–Bi2O3–MoO3 System with Ultra-Low Sintering Temperatures

Colossal Permittivity Materials as Superior Dielectrics for Diverse Applications

Dielectric properties of CaCu3Ti4O12 ceramics modified by SrTiO3

Microwave synthesis of high dielectric constant CaCu3Ti4O12

The microwave dielectric properties of the (1-x)CaTiO 3 - x Ca(Zn 1/3 Nb 2/3 )O 3 ceramic system have been investigated. The ceramic samples sintered at 1300°-1450°C for 4 h in air exhibit orthorhombic pervoskite and form a complete solid solution for different x value. When the x value increased from 0.2 to 0.8, the permittivity e r decreased from 115 to 42, the unloaded quality factor Q × f increased from 5030 to 13030 GHz, and the temperature coefficient τ f decreased from 336 to -28 ppm/°C. When x = 0.7, the best combination of dielectric properties, a near zero temperature coefficient of resonant frequency of τ f ∼ -6 ppm/°C, Q×f∼10 860 GHz and e r ∼51 is obtained.

Hongtao Yu

Papers

Dielectric properties of CaCu3Ti4O12 ceramics modified by SrTiO3

Microwave synthesis of high dielectric constant CaCu3Ti4O12

Dielectric Properties of (1−x)CaTiO3–xCa(Zn1/3Nb2/3)O3 Ceramic System at Microwave Frequency

Excellent energy storage and hardness performance of Sr0.7Bi0.2TiO3 ceramics fabricated by solution combustion-synthesized nanopowders

Effect of V2O5 additive to 0.4SrTiO3–0.6La(Mg0.5Ti0.5)O3 ceramics on sintering behavior and microwave dielectric properties