  Silicon carbide dust grains are ubiquitous in circumstellar envelopes around
C-rich AGB stars. However, the main gas-phase precursors leading to the
formation of SiC dust have not yet been identified. To date, only three
molecules containing an Si--C bond have been identified to have significant
abundances in C-rich AGB stars: SiC$_2$, SiC, and Si$_2$C. The ring molecule
SiC$_2$ has been observed in a handful of evolved stars, while SiC and Si$_2$C
have only been detected in the C-star envelope IRC +10216. We aim to study how
widespread and abundant SiC$_2$, SiC, and Si$_2$C are in envelopes around
C-rich AGB stars and whether or not these species play an active role as
gas-phase precursors of silicon carbide dust in the ejecta of carbon stars.
