CS244158B1 - Method of yttrio-aluminium garnet's single crystals cultivation,doped with molybdenum ions - Google Patents

Abstract

Method of growing yttritohumina monocrystals garnets, doped with molybdenum ions β content up to tenths by weight % of molybdenum ions and distinct spectra, corresponding to their incorporation in lattice-like ions and suppressed by creating color centers, which brings considerable benefits in using these single crystals in laser technology and at detecting ionizing radiation where the target is achieved by being grown from the melt composed of yttrium oxides, aluminum oxides and, where appropriate, molybdenum crucible neodymium and raw material contains an admixture of 0.0003 to 0.1 wt. % of phosphorus based on the starting material, wherein the protective atmosphere is formed a mixture of 2 to 50 vol% hydrogen and 98 to 50 vol. % argon.

Description

The present invention relates to a process for the cultivation of molybdenum-doped yttrium-aluminum garnet monocrystals, wherein the resistance to the formation of undesired colored uenteres is increased.

The increased importance of yttrium-aluminum garnet single crystals as active materials for lasers undermines further development of cultivation methods. At the same time, the economically advantageous method of melt cultivation using molybdenum crucibles provides the possibility of doping said monocrystals with molybdenum ions. Using a perfectly pure protective atmosphere composed of noble gas and hydrogen, molybdenum dissolution in the melt practically does not occur and the monocrystals contain molybdenum more than the corresponding neutron activation analysis, i.e. less than 10%. %. Water vapor in slight conetration causes the dissolution of nolybdenum and its transfer to the growing single crystal, where its concentration can reach hundredths of a weight% without haze formation; when the water vapor content of the protective atmosphere is increased, the single crystal contains foreign-metal particles which render it devoid of any optical application, so that higher concentrations of nolybdenum present in the ionic form in the single crystal cannot be achieved by humidifying the protective atmosphere.

This deficiency can be remedied by the cultivation of molybdenum-doped yttrium-aluminum garnet monocrystals by melt cultivation consisting of yttrium oxides, aluminum oxides and possibly neodymium contained in molybde244 158 novel crucible according to the invention, characterized in that it is cultivated from melt containing admixture 0 The protective atmosphere consists of a mixture of 2 to 50 vol.% Hydrogen and 98 to 50 vol.% Argon.

In this process, molybdenum in the form of ions, molybdenites 10 to 10 is obtained, up to a concentration of tenths by weight without any haze. At the same time, the single crystal contains phosphorus ions, apparently incorporated as trivalent ions, at a concentration approximately ten times lower than that of molybdenum ions, which does not adversely affect the quality of the monocrystals grown. Monocrystals have a green color after cultivation, corresponding to relatively wide absorption bands with maxima at 383 and 670 nm, after oxidation annealing they are colorless and after annealing in hydrogen they have the same color as after cultivation. Unlike monocrystals grown in a humid protective atmosphere ultraviolet light does not induce color centers, lato arise only when a single crystal contains in addition to molybdenum other ions.

By the method of the present invention, single crystals of yttrium aluminum garnet containing up to tenths by weight of molybdenum lions have a distinct spectrum corresponding to their incorporation in the trivalent ion lattice and suppressed color center formation, which brings considerable advantages when using these single crystals in laser technology or in ionizing detection radiation.

Example 1

Single crystals of yttrium-aluminum garnet with a diameter of 25 mm and a length of 75 mm by the Czochralski method were grown using molybdenum kernels with an inner diameter of 50 mm and a height of 60 mm under a protective atmosphere consisting of a mixture of 8 vol% hydrogen and 92 vol% argon. Default-

244,158 na contained sintered aluminum hydroxide and yttrium oxalate prepared by the garnet phase Y 2 Al 2 O 4, to which yttrium phosphate was added in an amount corresponding to 0.006 haot% phosphorus, based on the starting material. The cultivated green monocrystals contained approximately 0.006 wt% molybdenum ions and were completely free of foreign phase inclusions. Monocrystals grown in exactly the same way, ¹ from the same batt but without phosphorus, contained inclusions and were not optically humogenous.

Example 2

Single crystals of yttrium aluminum garnet with a diameter of 30 mm and a length of 100 mm by the Czochralski method were grown using a molybdenum crucible with an inner diameter of 75 mm and a height of 80 mm under a protective atmosphere consisting of a mixture of 30 vol% hydrogen and 70 vol% argon.

The feedstock contained alumina, yttrium, and neodymium in a molar ratio of 5: 2.85: 0.15 and was added with 0.8 mol% yttrium phosphate based on yttrium oxide, i.e. 0.06 wt% phosphorus based on the starting material. The single crystals produced contained 0.8 at.% Neodymium and 0.04 at.% Molybdenum based on yttrite, and the laser rods produced from these single crystals exhibited 30% higher efficiency in the laser pulse operation than the same rods produced from single crystals grown in the same way, but from raw material without phosphorus.

Claims (1)

A process for the cultivation of yttrium aluminum garnet monocrystals doped with molybdenum ions from a melt consisting of yttrium, aluminum and optionally neodymium oxides contained in a molybdenum crucible, characterized in that the melt contains 0.0003 to 0.1 wt.% Phosphorus based on the feedstock, the protective atmosphere consists of a mixture of 2 to 50 vol% hydrogen and 98 to 50 vol% argon.