Micrometer-sized particles of cadmium carbonate (cores) were prepared by homogeneous precipitation from aqueous solution containing urea in the presence of cadmium sulfate. These particles were then homogeneously coated with a layer of nickel hydroxy carbonate by heating their dispersion in aqueous solution, containing nickel sulfate and urea, at 85 degrees C for 70 min with constant agitation. The same solution mixture produced spheroids of nickel hydroxy carbonate (coating precursors), when heated under similar conditions in the absence of the cadmium carbonate particles. The existence of the coated layer on the cores and its composition was confirmed by various physical methods. The as-prepared carbonated solids (cores, coating precursors, and coated particles) were converted into their oxide forms by calcination at 700 degrees C. The cores became porous, whereas the coating precursors and coating layer disintegrated into smaller particles during the calcination process.