Growth of Large Single Crystals. Ce2Mg3(NO3)12·24H2O (CMN)

Abstract

An apparatus and method is described for the growth of large, flawless, high‐purity, oriented, single crystal cylinders (at least 50 mm in diameter by 55 mm long) of cerous magnesium nitrate 24 hydrate [Ce2Mg3(NO3)12·24H2O; (CMN)]. The CMN single crystals are grown at 30 °C in an air thermostat by evaporation of a saturated aqueous solution using reagent H2SO4 (98 wt %) as a desiccant for H2O removal. Growth is in a cylindrical container with the c crystal axis oriented parallel to the cylinder axis. The container and crystal orientation limit growth in the fastest growing directions perpendicular to the c axis. Rate of growth parallel to the c axis is set at 0.9 mm/day. Large single crystals are assured provided the procedure described is followed rigorously. Fabrication of the CMN cylinders into spheres and the location and marking of the crystal axes are also described. A spark source mass spectrometeranalysis of pieces of such CMN crystals gave an impurity level expressible as 615 < atomic ppm impurities <1710 (atomic ppm relative to Ce). It is suggested that the apparatus and method may find general use in the growth of large single crystals of other substances, perhaps with a modification to allow continuous solution addition.