The synthesis of Al28C6O21N6 powder (ALCON), starting from the binary compounds is described. The powder is resistant to oxidation in air up to 760 degrees C. From the prepared powder, fully dense ceramics have successfully been prepared using hot pressing. The as-prepared ceramics had a thermal conductivity of 20Wm(-1)K(-1). Experiments showed that it is also possible to prepare ALCON ceramics by reactive hot-pressing, starting from Al2O3, AIN and Al4C3. Further optimization is expected to raise the thermal conductivity significantly. The strength, about 300 MPa, is similar to that of AIN. The thermal expansion coefficient of 4.8 x 10(-6)K(-1) closely matches that of silicon, making application of ALCON ceramics as heat sinks an interesting possibility.