Regularly shaped single-crystalline, hexagonal, and hollow Sr-Er- and Sr-Dy-sialon microtubes were yielded by high-temperature reaction using a radio-frequency furnace at 1600 degrees C and 1670 degrees C, respectively. Starting materials were silicon diimide (Si(NH)(2)), AlN, Sr and Er or Dy, respectively. The carbonates Er-2(CO3)(3) and SrCO3, respectively, have been used as oxygen providing reactants. The sialon microtubes had an average diameter between 3 and 25 mu m and an average length between 30 and 150 mu m.