**5. Acknowledgement**

The authors wish to thank Telekom Malaysia for their funding support under project IMPACT (RDTC/100745) and Assoc. Prof. Dr. Mansor Hashim, Mr. Ismayadi Ismail and Mrs. Sabrina Mohd. Shapee for the guidance and support for this research work.

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**4** 

*PR China* 

**Microwave Sintering** 

Aimin Chang1, Huimin Zhang1, Qing Zhao1 and Bo Zhang1,2

**of Thermistor Ceramics** 

*1Xinjiang Key Laboratory of Electronic Information Materials and Devices, Xinjiang Technical Institute of Physics and Chemistry. CAS, Urumqi* 

Microwave sintering is a new sintering technology developed in the middle to late period of the 1980's, which is characterized by fast densification for ceramic materials[1]. In recent years, microwave heating has been well employed in the field of sintering and joining of ceramics as a result of its advantages against conventional methods. These ceramic materials include oxides, mixed oxides, non-oxides, composite ceramics, etc[2]. In addition, because ceramics have low thermal conductivities and are processed at high temperatures, many researchers have attempted to take advantage of volumetric heating for sintering, chemical vapor infiltration (CVI), and pyrolysis of polymeric precursors[3]. Now it has been found that the microwave sintering can also be applied as efficiently and effectively to thermistor ceramics as well as many other ceramics. This chapter compares advantages of microwave sintering with conventional sintering and presents some applications in thermistor ceramics.

Microwave is the name given to electromagnetic radiation 1 m to 1 mm in wavelength that corresponds to a frequency of about 300MHz to 300 GHz. Microwave heating is a process in which the materials couple with microwaves, absorb the electromagnetic energy volumetrically, and transform into heat. This is different from conventional methods where heat is transferred between objects by the mechanisms of conduction, radiation and convection[4]. In conventional heating, the material's surface is first heated followed by the heat moving inward. This means that there is a temperature gradient from the surface to the inside. However, microwave heating generates heat within the material first and then heats

Microwave sintering makes use of dielectric loss of materials in microwave electromagnetic fields to heat ceramic matrix to the sintering temperature fast. The microwave sintering

**2. Theoretical aspects of microwave sintering** 

**1. Introduction** 

the entire volume[5].

**2.1 The principle of microwave sintering** 

*2Graduate School of the Chinese Academy of Sciences, Beijing* 

