Space and Satellite Technology: AlN ceramic has other interesting characteristics apart from good heat conduction. Firstly, its specific weight of 3.3 grams per cubic centimetre is 25 percent lighter than aluminium oxide. Secondly, its thermal expansion coefficient of about 3 times ten to the minus sixth is less than half that of aluminium oxide, a third that of beryllium oxide and is in fact very close to silicon. The low coefficient of expansion and good heat conducting properties guarantee high stability under changing temperature conditions and thermal shock resistance.