RUDN University chemists discovered the mechanism of radiation instability of lithium tetraborate

RUDN University chemists discovered the mechanism of radiation instability of lithium tetraborate

Chemists from RUDN University have studied the mechanism of radiation instability of thermoluminophores based on lithium tetraborate, which are used for the manufacture of radiation dosimeters. They found that the properties of the materials are deteriorating due to the breakdown of chemical bonds in the boron-oxygen network and the formation of clusters of manganese, which is part of the substances.

Lithium tetraborate was the first material thermoluminescent radiation dosimeters, which were highly sensitive to x-ray, gamma, and beta radiation, were made of. When ionising radiation enters a thermoluminescent dosimeter, the latter “stores” the absorbed energy due to the transfer of electrons to higher energy levels. When heated above a certain temperature, the electrons emit previously absorbed energy, and the dosimeter begins to glow. The light intensity is proportional to the amount of absorbed radiation. In order to make lithium tetraborate capable of this, impurities of manganese, silver, or other metals are introduced into it, which act as traps for those electrons that were excited by ionising radiation. But because of these impurities, the radiation resistance of the substance decreases. It has not been known why, until now.

RUDN University chemist Alexander Zubov and his colleagues compared ceramic samples based on lithium tetraborate with impurities of manganese, copper, zinc, tin, and beryllium. It turned out that the radiation stability of the substance is deteriorating due to the rupture of chemical bonds in the boron-oxygen network. And while the boron-oxygen lattice in a pure substance is capable of restoring itself during heating, the introduction of manganese interferes with this process.

The more evenly manganese is distributed in the structure of lithium tetraborate, the less negative impact it has on the radiation stability of the material is. Copper and tin prevent the clustering of manganese, forming bound complexes with it, thereby preventing it from “migrating” and “sticking” to the crystal lattice during recharging of the dosimeter. Moreover, ceramics with addition of tin, unlike of copper, also has thermoluminescent properties that allow its effective use in dosimetry.

Understanding of the physicochemical processes that occur during irradiation of a material is necessary to create new radiation resistant materials. The RUDN University chemists were able not only to explain the mechanism of radiation destruction of lithium tetraborate, but also to apply the new knowledge to create a material with a better composition, which can later be used in advanced pocket radiation dosimeters. In addition, the authors argue that their experimental approach, which involves searching for clustered manganese in the structure of lithium tetraborate, can be used as a new effective way to certify the radiation resistance of thermoluminescent dosimeters.

The work was published in the journal Radiation Measurements.

All news
18 Feb
RUDN University physicists analyzed the role of gravity in elementary particles formation

Gravity might play a bigger role in the formation of elementary particles than scientists used to believe. A team of physicists from RUDN University obtained some solutions of semi-classical models that describe particle-like waves. They also calculated the ratio between the gravitational interaction of particles and the interaction of their charges.

15 Feb
Iron Is to Blame for Carbon Dioxide Emissions from the Soil, Says a Soil Scientists from RUDN University

Iron minerals and bacteria can be the main agents of carbon dioxide emissions from the soil. A soil scientist from RUDN University made this conclusion after studying the process of organic plant waste decomposition of the micro-level. Iron and hydrogen peroxide enter into a reaction, as a result of which active oxygen forms (oxygen radicals) are formed. The radicals destroy plant waste in the soil and promote carbon dioxide emissions.

10 Feb
RUDN University Soil Scientist: Deforestation Affects the Bacterial Composition of the Soil

A soil scientist from RUDN University studied the effect of forest conversion on the properties of the soil: its acidity, carbon and nitrogen resources, bacterial composition, and the activity of microorganisms. The study can help improve the methods of soil cultivation after deforestation, namely, select the best fertilizers, prevent erosion, slow down nutrient depletion, and balance the composition of the bacterial community.