A series of Li deficient LiTi2(PO4)3 samples were prepared and sintered and the density was measured to determine the rate-controlling species for sintering of LiTi2(PO4)3. It was observed that as the Li content decreased the density decreased. This result suggests that oxygen does not control sintering. A comparison of the LiTi2(PO4)3 sintering data to sintering and diffusion data in olivine, which exhibits a similar framework structure to LiTi2(PO4)3, suggests that P is the species which controls sintering. This suggestion was confirmed by the density results of a Li excess LiTi2(PO4)3 sample.