Stoichiometric Silicon Nitride/Silicon Carbide Composites from Polymeric Precursors

A partially methylated highly branched polysilazane Si4N4CH9 is the first single-source precursor for stoichiometric Si3N4/SiC. Thermolysis delivers amorphous Si4N4C and H2 as the only gaseous by-product. Upon stepwise heating to 1900 °C, Si4N4C gradually crystallizes in the order α-Si3N4, β-SiC, and finally β-Si3N4, whereas at 2000 °C a fully crystalline α-Si/β-Si3N4/β-SiC composite is obtained (see Figure).