**1. Introduction**

Microwave sintering (MWS) is emerging and an innovative sintering technology for process‐ ing of ceramic materials and is commonly related with volumetric and uniform heating. MWS is one of the exciting new fields in material science with vast potential for preparation of novel and/or nanostructured ceramics/materials. Microwave heating has some important benefits

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over normal heating for ceramic processing, including reduced processing time, higher energy efficiency, selective and controlled heating, environmental friendliness, and improved product uniformity and yields. Microwave processing of materials is a relatively new technology that can be used in wide range of different materials such as ceramics, ferroelectrics, oxides, metals, and composites [1–10].

The effect of microwave radiation on the processing of several ceramic materials such as magnetic materials, superconducting materials, dielectric materials, metals, polymers, ceramics, and composite materials offers numerous benefits over conventional heating techniques. These benefits include time and energy savings, volumetric and uniform heating, considerably reduced processing time and temperature, improved product yield, fine micro‐ structures, improved mechanical properties, lower environmental impact, reduction in manufacturing cost, and synthesis of new materials [11].

Microwave sintering has developed in recent years as a promising technology for faster, cheapest and most environmental-friendly processing of a wide variety of materials, which are regarded as significant advantages over conventional sintering procedures. Microwave radiation/heating for sintering of ceramic constituents has recently appeared as a newly motivated scientific approach [5].

Microwave sintering approach has unique advantages over conventional sintering methods in many respects. The essential difference in the conventional and microwave sintering processes is in the heating mechanism (Figure 1). In microwave heating, the materials them‐ selves absorb microwave energy and then transform it into heat within the sample volume and sintering can be completed in shorter times. In microwave sintering, the heat is generated internally within the test sample due to the rapid oscillation of dipoles at microwave frequen‐ cies [12]. The contribution of diffusion from external sources is lesser. The internal and volumetric heating makes the sintering rapidly and uniformly. The heat generated through conventional heating is generally transferred to the sample via radiation, conduction, and convention [13]. This process takes longer duration for sintering the materials and causes some of the constituents to evaporate. This may lead to modify the desired stoichiometry and grain.

**Figure 1.** Comparison of heating mechanism in microwave and conventional sintering methods.

In contrast, microwave energy is transferred directly to the material through molecular interaction with an electromagnetic field. Microwave heating is more effective than conven‐ tional methods in terms of the usage of energy, produces higher temperature homogeneity, and is considerably faster than conventional heat sources. In the last 8 years, we have success‐ fully sintered various ferrites/ferroelectrics, oxides, ceramics, mullite fiber, composites, and even powdered metals to full density using microwave processing [4, 5, 14–16].

over normal heating for ceramic processing, including reduced processing time, higher energy efficiency, selective and controlled heating, environmental friendliness, and improved product uniformity and yields. Microwave processing of materials is a relatively new technology that can be used in wide range of different materials such as ceramics, ferroelectrics, oxides, metals,

The effect of microwave radiation on the processing of several ceramic materials such as magnetic materials, superconducting materials, dielectric materials, metals, polymers, ceramics, and composite materials offers numerous benefits over conventional heating techniques. These benefits include time and energy savings, volumetric and uniform heating, considerably reduced processing time and temperature, improved product yield, fine micro‐ structures, improved mechanical properties, lower environmental impact, reduction in

Microwave sintering has developed in recent years as a promising technology for faster, cheapest and most environmental-friendly processing of a wide variety of materials, which are regarded as significant advantages over conventional sintering procedures. Microwave radiation/heating for sintering of ceramic constituents has recently appeared as a newly

Microwave sintering approach has unique advantages over conventional sintering methods in many respects. The essential difference in the conventional and microwave sintering processes is in the heating mechanism (Figure 1). In microwave heating, the materials them‐ selves absorb microwave energy and then transform it into heat within the sample volume and sintering can be completed in shorter times. In microwave sintering, the heat is generated internally within the test sample due to the rapid oscillation of dipoles at microwave frequen‐ cies [12]. The contribution of diffusion from external sources is lesser. The internal and volumetric heating makes the sintering rapidly and uniformly. The heat generated through conventional heating is generally transferred to the sample via radiation, conduction, and convention [13]. This process takes longer duration for sintering the materials and causes some of the constituents to evaporate. This may lead to modify the desired stoichiometry and grain.

**Figure 1.** Comparison of heating mechanism in microwave and conventional sintering methods.

and composites [1–10].

2 Advanced Ceramic Processing

motivated scientific approach [5].

manufacturing cost, and synthesis of new materials [11].

Due to the energy efficient nature of microwave heating, there is a great opportunity for the application of microwaves to process metal based materials to couple the many gains of microwave heating. Recently, microwaves energy has been successfully used in different composites, metal, ceramics, melting of metals and metal ores, joining or brazing of metals, and heat treatment of metals [17].

The microwave energy is highly versatile in its application in the field of communication, and it still dominates almost all communications in space and mobile or cordless phone technology involves microwave frequencies. However, other than this communication, microwave energy has found its use for a variety of applications including rubber products industry, food processing, wood/paper/textile/ceramic drying, pharmaceuticals, polymers, printing materi‐ als, and biomedical fields over the past 50 years. These applications involve low temperature (<500°C) utilization of microwaves. The high temperature (> 800°C) applications of micro‐ waves are a rather recent phenomenon.

Many researchers have reported that microwave heating is relatively faster than the conven‐ tional heating processes. This faster speed is manifested as a reduction in the densification time of ceramic powder compacts, often allied to lower sintering temperatures [7]. Generally, the synthesis kinetics and sintering materials are apparently upgraded by two or three orders of magnitude or even more when conventional heating is switched for microwave heating [18].
