Introduction

Alumina (Al2O3) is one of the most important ceramic materials, both pure and as a ceramic and glass component. Some uses of alumina are given in Table 1; an exhaustive and detailed description of many of these uses is given in [1]. There are also extensive dis­cussions of uses of alumina in [2]. Processing of alumina is discussed in both these refer­ences, and [2] has a summary of some properties of alumina. In writing this review, I have relied on material from these references. Anyone interested in more details of processing and properties of alumina should obtain [2] from the American Ceramic Society. Reference [1] is also available from the Society and has additional information on processing and uses of alumina. More recently, there have been two issues of the Journal of the American Ceramic Society devoted to alumina [3, 4]; these issues concentrate on defects and inter­faces, especially grain boundaries [3], grain growth, and diffusion in alumina [4].

The usefulness of alumina derives from a variety of its properties. It has a high melting temperature of 2,054°C, and is chemically very stable and unreactive, leading to applications as high-temperature components, catalyst substrates, and biomedical implants. The hardness, strength, and abrasion resistance of alumina are among the highest for oxides, making it useful for abrasive materials, bearings,

J. F. Shackelford and R. H. Doremus (eds.), Ceramic and Glass Materials: 1

Structure, Properties and Processing.

© Springer 2008

Furnace components

Catalyst substrates

Electronics substrates

Electrical insulators

Cutting tools

Bearings

Spark Plugs

Arc lamp tubes

Laser hosts

Gem stones

Alumina powders

Abrasives Catalyst pellets

Alumina coatings Oxidation protection of aluminum and aluminum alloys Capacitors Transisitors Bioceramics Alumina fibers

Thermal insulators Fire retardation Alumina as a component of Ceramics and glasses Mullite components Electrical insulators Porcelains Durable glasses

and cutting tools. The electrical resistance of alumina is high, so it is used pure and as a component in electrical insulators and components. Alumina has excellent optical transparency, and along with additives such as chromium and titanium, it is important as a gem stone (sapphires and rubies) and a laser host (ruby). Because of its high melting temperature, chemical inertness, and optical transparency, it is highly useful for containing arcs in street lamps. See Table 1 and also [1, 2] for more on uses of alumina.

In this review, the processing of alumina is discussed next, and then its properties are tabulated and described. In a summary future uses of alumina are considered.