Carriers were successfully doped into RbCa 2 NaNb 4 O 13 by the substitution of Sr 2+ for Na + , yielding electroconducting niobates with a layered structure consisting of four perovskite-like layers. Single-phase products of polycrystalline RbCa 2 Na 1−x Sr x Nb 4 O 13 (x=0.2 and 0.4) were synthesized by the solid-state reaction of RbCa 2 Nb 3 O 10 , Sr 5 Nb 4 O 15 , Nb 2 O 5 , and Nb metal. The solid solutions were indexed based on a tetragonal structure, corresponding to the end-member RbCa 2 NaNb 4 O 13 . With the increase in the amount of strontium substitution, an expansion of the c-axis was observed while the a-axis was essentially constant. The products showed semiconducting properties.