Thorium bismuthide when crystallized from a solution i bismuth results in large platelets which may be as large a 1 centimeter in diameter. A slurry of these platelets is difficult to pump through pipe lines and filters. The particle size can be reduced by (1) very rapid cooing (approximately 1000 degree C per second) or (2) ultrasonic treatment. The latter, much easier to attain in large scale, gives equiaxed particles of thorium bismuthide.