At present one can hardly find a branch of science or technology where this crystal is not used. Demand for sapphire grows year after year, almost exponentially.

Devices and their components applied in aviation and space industries, in chemical processing, and in many other fields are simultaneously subjected to the action of aggressive media, radiation, high temperatures, pressures, and mechanical loads. Under such extreme conditions any material is prone to intense corrosion and erosion. High-strength alloys have reached the practical limits of their capabilities. The structure of polycrystalline materials and consequently their mechanical properties essentially change under extreme conditions due to recrystallization, corrosion of the grain boundaries, and so forth.

The rate of diffusion via the grain boundaries grow with increasing temperature, radiation dose, and operation time. As a result, the material breaks down. Such drawbacks are inherent in sapphire components and assemblies to a considerably lesser extent. There are two classes of modern articles made of sapphire: constructional and functional. Constructional sapphire is used for the creation of products with high mechanical stability. Functional sapphire has a specific structure and electrical, optical, and thermal properties. This classification is arbitrary, as this material is multifunctional, and sapphire articles (such as rocket nose cones) often combine the two functions. Constructional and functional sapphires are comparatively new materials, so the scale of their production compares unfavorably with that of traditional materials.

At the same time, the rate of growth in their production far exceeds that of steel, aluminum, and some other materials. It also should be emphasized that sapphire is used in complex technical systems with costs several times as high as that of the sapphire elements.

At present, the greater part of artificial sapphire is used as a functional material. However, extremely high production rates are predicted for constructional sapphire as well. This follows from estimations made by specialists in the world’s leading firms. According to the performed analysis, in 70% of cases future prospects for the use of sapphire are tied to its mechanical, thermal, and chemical properties.

For a long time sapphire has not been considered by material scientists to be a possible constructional material due to the fact that its treatment is both complicated and expensive. After the appearance of a wide variety of profiled sapphire, such a problem is not as relevant. However, purely physical obstacles in the use of sapphire as a constructional material still exist. First, this is the main disadvantage of sapphire – its brittleness. Concerning other significant working parameters such as thermal stability, hardness, corrosion resistance, and density, as well as availability and low price of raw material, sapphire compares favorably with metals, alloys, and some ceramics. The tendency of sapphire to brittle failure is associated with low defect mobility, which is a primary result of the specific ionic-covalent bonding of this material. Therefore, a good deal of effort now is being undertaken by researchers to eliminate the microscopic defects that function as crack nucleation centers in sapphire upon loading.

As shown by the last decade of the development of the sapphire industry and the corresponding application fields, interest in both constructional and functional sapphire has grown to a great extent. One may even say that such a “renaissance” of sapphire is one of the most significant tendencies in modern materials science. This is caused by many factors. Here are several:

• Sapphire is a multifunctional material
• The raw material for sapphire production is readily available and cheap
• As a rule, the technology of sapphire production is less energy-intensive than alternative materials and allows the growth of large-size crystals
• Sapphire production does not pollute the environment. The growth of sapphire is less harmful than that of alternative materials due to the absence of processes such as electrolysis, pyrometallurgy, the action of aggressive media, and other factors
• Compared to other materials, sapphire possesses higher corrosion and radiation resistance, which results in operational longevity of sapphire articles in aggressive media
• Sapphire is characterized by higher biological compatibility than metals and polymers; therefore it is used in medical implants, as a constructional material in biotechnology, in medical instrument-making, and in genetic engineering

Today, sapphire primarily is used for:

• Fabrication of substrates for light-emitting diodes, new generations of TV receivers, projectors, and microwave devices
• Fabrication of windows for civilian and military equipment
• Production of bearings and windows for watches and devices
• Making of precious jewels for the jewelry industry

The light sources in which light-emitting diodes are used instead of filament lamps allow reduction of electric power consumption by approximately ten times. It has been calculated that the funds that could be saved due to the substitution of conventional light sources by light diodes in all the world’s lighting systems would be equivalent to the cost of several hundred nuclear power stations!

The immense output of present-day TV receivers, mobile phones, and other household appliances that contain or will contain sapphire components speaks for itself. The statement to the effect that the technologies using sapphire articles have penetrated into practically all the spheres of science and engineering is confirmed by an analysis of the recently published book “History of Science and Engineering” (2004, Houghton Mifflin) and the patents granted in the world from 1990 to present. Approximately 5–7% of these publications are in some way related to sapphire.

Over the past few years, the range of manufactured sapphire items has sharply increased and the requirements for the quality of their working surfaces have become more stringent. Therefore, special attention is being concentrated on the possibility of controlling the structure perfection not only in the process of sapphire growth, but also during subsequent thermo- and mechanochemical treatment. Much effort also is being undertaken to investigate thermal power effects on the structure evolution of sapphire articles to develop basically new sapphire treatment methods.

Now let us outline the near future for sapphire. The present-day market for synthetic stones is estimated to exceed $6 billion. In the world ~300 tons of rubies and colored sapphires and 100 tons of sapphire are produced. In the opinion of specialists, by 2008 the world market of synthetic crystals will reach $11.3 billion; the share of sapphire being about one quarter of this value. The growth rate of sapphire production is extremely high. One should expect that during the next 20 years the world production of sapphire will increase approximately tenfold. Currently, the leading manufacturers of sapphire are the United States and Russia. In the United States, sapphire crystals are grown by the Czochralski, Kyropoulos, HEM, and EFG methods. In Russia the Kyropoulos and Stepanov methods dominate. The rate of sapphire production is being stepped up in the Ukraine and Japan. China is endeavoring to hit the world market, too. At present, the annual increase in the production rate of sapphire articles in China is ~20%. However, the quality of these products is still insufficient.

Since the beginning of 2004, contradictory tendencies have been observed for the world sapphire market. During the past 5 years the world production of sapphire has increased by ~10% annually, whereas during the past 2 years the average growth in demand for this material and articles based on it have exceeded 15–20%. At the same time, technical requirements for the quality of the material itself and the working surfaces of sapphire articles become ever more stringent. The performed analysis indicates that one of most important problems for the development of sapphire production is the increase in the size of the crystals. This is explained not only by economic considerations, but also by technical requirements. Large-size sapphire crystals are needed for optics and airborne windows with apertures of 600 mm and larger (for the medium-wave IR region of the spectrum). At present, the only material used for the windows with a diameter greater than 300 mm is ZnSe. Its ultimate strength reaches 69 MPa (10,000 psi). Large-size windows have a thickness of 20 mm or more, and such a thickness makes the windows heavy and expensive. Moreover, it gives rise to an essential optical scattering.

5 mm with a complete absence of optical scattering. As shown by recent investigations, large area (500 × 500 mm and 1,000 × 1,000 mm) is necessary for making transparent armor used for the windows of helicopters, special-purpose vehicles, and so forth Work in the creation of this kind of armor has been started in the United States, Russia, Ukraine, Czech Rep., and other countries. The strength of a “glass sandwich” with a thickness of 25–35 mm will correspond to that of ~100-mm-thick armored glass. The upper layer of such a “glass sandwich” would contain a sapphire sheet meant to absorb the greater part of the kinetic energy of bullets. The rest of this energy will be absorbed in the layers of glass and plastic. The growth of large-size sapphire crystals is an urgent problem. Required for this purpose are large crystallization units that provide not only high perfection of the crystals, but also quantity production. The use of such units essentially decreases consumption of both energy and materials, so the cost of the crystal diminishes. The growth of one crystal with a weight of 30, 100, 200, and even 500 kg is more profitable than the growth of the corresponding quantity of smaller crystals. Thus, it is to be concluded that in the near future sapphire, as with silicon and germanium, will become one of the strategic materials for materials science. The main trends in the development of the sapphire industry will be the increase in the size of the grown crystals and the creation of technologies for obtaining permanent sapphire joints.