Abstract

Crystals of alkali metal tungstates are widely used as photonic materials due to their physico-chemical stability, wide transmission range, and relatively low cost. Since bulk boules with a size of 40 mm are required for the creation of scintillators, it is necessary to develop new approaches to crystal growth under conditions of low temperature gradients. This method is the low-gradient Czochralski method, which allows for the production of homogeneous crystals with a lower number of structural defects and thermoelastic stresses.

Method

The feedstock was loaded into a crucible, then melted in a sealed chamber with a thermoinsulation installed above the crucible with a pipe. Immediately before the crystal growth process, the melt was kept at a temperature slightly above the melting point to homogenize the melt. The seed is a single crystal of high structural perfection with a minimum density of dislocations, which is cut in a strictly defined crystallographic direction. The seed was immersed in the melt. The process of crystal stretching began with the formation of a monocrystalline neck, immersing the seed into the melt. The neck was formed by simultaneously lowering the melt temperature at a high linear velocity and large axial temperature gradients. Once the crystal reaches the desired diameter, the growing conditions should be stabilized to ensure a constant crystal diameter and high structural perfection.

Results

We have successfully grown Na₂W₂O₇ crystals using the low-temperature gradient Chochralski method and measured the excitation and emission spectra of the crystal.

Conclusion

Growing crystals of alkali metal tungstates using the Chochralski method with low temperature gradients is a effective method for growing single crystals. The advantages of this method include the ability to change the crystal's geometric shape and the reduction of temperature gradients, which allows for the production of larger crystals with high optical quality.