CS233264B1 - Method of corundum preparation for dosimettering purposes - Google Patents

Abstract

A method for preparing corundum for dosimetric purposes with highly stable dosimetric properties, which is achieved by heating aluminum oxide containing 10"3 to 10° wt. % alkaline earth ions •5 -2 and optionally 5.10 to 10 wt. % titanium ions to a temperature of 1000 to 1800 °C for a period of 0.5 to 30 h in an atmosphere containing free oxygen and subsequent heating to a temperature of 1200 to 2000 °C for a period of 0.5 to 15 h in an atmosphere containing free hydrogen.

Description

Back ^and reindeer preparation of alumina for dosimetric purposes

Process for preparing corundum for dosimetric purposes with highly stable dosimetric properties, which is achieved by heating alumina containing

10 ° ^3-10 wt. % of alkaline ions • 5 -2 soils and optionally 5.10 to 10 wt. % of titanium ions at a temperature of 1000 to 1800 ° C for 0.5 to 30 h in an atmosphere containing 20% by weight of titanium ions; free oxygen followed by heating to 1200 to 2000 ° C for 0.5 to 15 h in a free hydrogen atmosphere.

- 2 233 264.

The present invention relates to the preparation of corundum suitable as a material for thermolumination reaction dosimeters.

Corundum is a suitable material for the detection of ionizing radiation on the principle of thermoluminescence. At present, a number of ways how thermoluminescence properties are influenced by the composition and content of color centers or vacancies are described. A number of papers have also been published in which thermoluminescent materials are described, but the composition of the material and its processing is known incompletely or not at all. Of the known thermoluminescent materials, magnesium corundum appears to be a perspective.

The admixture of these ions substantially stimulates the thermoluminescent emission of corundum, but the undefined composition, respectively the thermal or previous radiation treatment precluded the practical use of this material. In practice, corundum with an admixture of magnesium ions is characterized by a high sensitivity, a simple course of thermoluminescence emission in blue-violet, for the detection of a favorable spectrum region and a high reproducibility of the measured values.

The corundum with the above properties can be prepared by the process according to the invention, characterized in that the alumina containing the admixture of 10 ^-3 to 10% by weight of alkaline earth ions is exposed to heating in an atmosphere containing 1 to 100 vol. 1000 to 1800 ° C for 0.5 to 30 h and then exposed to heating in an atmosphere containing free hydrogen at a temperature of 1200 to 2000 ° C for 0.5 to 15 h.

- 3 233 264

A first heating in the atmosphere, containing said sufficient amount of free rabbit, which can be conveniently combined with the preparation of aluminum oxide from other aluminum compounds, will create cationic vacancies in the alumina and eliminate excess metal ions common to melt prepared from melt under reducing conditions. By further heating in hydrogen, hydrogen ions are incorporated in the corundum lattice and the excess oxygen ions are removed. This creates a material that exhibits a good thermoluminescence response to the received dose of ionizing radiation with a single temperature peak at 150-200 ° C and emission in the blue region of the spectrum. The stability and / or reproducibility of the thermoluminescence response is further increased when the starting alumina contains 5.10 < -1 > to 10-2 wt% titanium ions.

By the process of the invention, corundum can be prepared for dosimetric purposes, either without light sensitivity or, if it contains a large amount of titanium, with light sensitivity but with otherwise extremely stable dosimetric properties.

Example 1

100 g of crystalline síraau hlinitoamonného NH ^ A1 (SO ^) ₂ .12H ₂ O and 2 g crystalline magnesium sulfate MgSO * 7H ₂ 0 was dissolved in water and the resulting solution was precipitated with ammonia, aluminum hydroxide, all containing added magnesium. The hydroxide was washed with water, dried and exposed to 1200 ° C in air for 6 h. Subsequently, the formed alumina was exposed to 1600 ° 0 in an atmosphere containing 75 vol% nitrogen and 25 vol% hydrogen for 12 h. the powdered corundum exhibited reproducible responses to X-rays and was used as a fill in glass tube dosimeters.

Example 2

Corundum monocrystals containing 0.003 wt% calcium and 0.0004 wt% titanium were grown by the Czochralski method in a neutral environment of pure helium and showed almost no thermoluminescence after irradiation with radiation from Co60

- 4 233 264 response. Therefore, they were first exposed to 1600 ° C in an atmosphere of oxygen for 25 h and then in hydrogen at 1950 ° C for 5 h. Single crystals were then made of 1 mm thick, 3 mm in diameter, which in view of high and good reproduction Frontal thermoluminescence response to ionizing radiation was used as the activating material of dosimeters.

SCOPE OF THE INVENTION 233 264

Claims (2)

SCOPE OF THE INVENTION 233 264 1. A process for the preparation of corundum for dosimetric purposes, characterized in that alumina containing from 10 to 10% by weight of alkaline earth ions is heated in an atmosphere containing from 1 to 100% by volume of free oxygen to a temperature of 1000 to 1800 ° C after sampling 0, 5-30 h, and then heated again to a temperature of 1200-2000 ° C for 0.5 to 15 h in an atmosphere containing free hydrogen _with 2. Method of claim 1, wherein the aluminum oxide contains in addition 5.10 * 5 _and * ^2? 10 wt% of titanium ions