Scintillation crystals of bismuth germanate

Know-how of Novosibirsk scientists provides world electronic industry with laser and scintillation crystals of extremely high quality.

Ultrapure silicon is god of materials for electronic needs. When electronic industry switched from vacuum lamps to transistors and later to microcircuits, pure semiconducting silicon was the key to making electronic devices smaller in size. Today purity standards for silicon are 1 alien atom for 1 billion atoms of silicon.

No doubts silicon crystals will become more and more perfect. A variety of new application for crystals, made of this element, will evidently appear, and composition and structure of these crystals will be controlled at nearly atomic level.

Know-how of the researchers from Novosibirsk is the technique for crystal synthesis with very delicate conditions of phase formation. Crystal formation requires melting of a substance, and then its ordered crystallization. During this process parts of the future crystal have great difference in temperature, which means thermal stress in the growing crystal can easily disturb order of atoms in its structure, thus destroying its quality.

Russian chemists developed a technique, which reduces temperature difference during crystallization by the order of two and maintains stability of the whole system. No one else in the world can do it with crystals. The history of the technology dates back to the USSR, when researcher fellows from the Institute of Inorganic Chemistry (Siberian branch of Russian academy of sciences) developed and introduced automated technologies for growing laser crystals and other types of crystals into industry. When financial crisis after USSR collapse left basic science with nearly nothing, researchers decided to produce scintillation crystals of bismuth germanate and to export them abroad.

Later on the Institute of Inorganic Chemistry became the leading Russian supplier of laser and scintillation crystals to the world market. Laser crystals are used in various laser devices, and scintillation crystals emit light, when absorbing ionizing radiation, like gamma-quanta. Russian scintillation crystals are demanded by medics for making positron-emission tomography scanners (PETs), and by geologists for exploring rocks and finding carbon-oxygen ratio in oil wells. Another application is safety, when they help quickly determine chemical composition of suspicious substances.

Crystals of bismuth germanate, which are made in Russia, are in high demand in the USA, Canada, Italy, and other countries. Radiation-prone crystals from Novosibirsk work in forward calorimeter on BELLE detector in Japanese nuclear centre KEK.  Four years ago about 400 high-quality crystals from Novosibirsk got a job in an international astrophysical project POGoLite, aimed at studying polarized gamma-radiation of our Universe.

Laser crystals from Novosibirsk are perfect for making coherent radiation with precisely controlled wavelength between 1 and 10 microns. Such lasers work in dentistry and vascular surgery.

Sad fact is that all these fantastic crystals find almost no applications in our home country. Moreover, the government tends to prohibit commercial operations in non-private institutions, like research institutes of Russian academy of sciences, which all belong to the state. Hope tolerant Russian science will survive once again.

Source: Science & Life

Anna Kizilova