Growth of MgWO₄Needle Crystals by KCl Flux Method

Abstract

Needle crystals of MgWO₄ were grown by cooling the high-temperature solution of MgW04 KCl mixture and crystal length was studied by means of photomicroscope. The MgWO₄KCl solution was heated to 900 or 1000°C for 5 hours and gradually cooled to about 500°C at a rate of 5°C/hr.
Results obtained were as follows ;
(1) Needle crystals of MgWO₄ were grown from the fluxed melt having the solute concentration from 1 to 15 mol% (soaking temperature 900°C) or from 2. 5 to 15 mol% (soaking temperature 1000°C).
(2) Needle crystal with the length of 5.7 mm and the diameter of 20 μ could be grown. The growth direction of the needle crystal was considered to be <100>. The needle crystals whose form was tetragonal prism had a silky luster and smooth surface.
(3) The relation between the length of needle crystal and solute concentration approximately followed Weimarn's theory.