Structural and Electronic Properties of a Triangular Lattice Magnet NaPrTe$_2$ Compared with NaNdTe$_2$ and NaTbTe$_2$

NaPrTe$_2$, NaNdTe$_2$, and NaTbTe$_2$ are found to be triangular lattice magnets with the alpha-NaFeO$_2$ structure, where lanthanoid atoms with 4f electrons form a triangular lattice, based on the structural analysis and physical property measurements of synthesized polycrystalline samples. The alpha-NaFeO$_2$ structure is a new polymorph of NaPrTe$_2$, which has been reported to crystallize in the cubic LiTiO$_2$ structure. Polytypism in NaPrTe$_2$ was discussed based on the structural parameters determined by the Rietveld analysis. NaPrTe$_2$ is suggested to be in the proximity of the phase boundary between the LiTiO$_2$ and alpha-NaFeO$_2$ types, as compared to NaNdTe$_2$ and NaTbTe$_2$, indicating that this compound might be interesting from the perspectives of the dimensional control of geometrically frustrated lattices. The magnetic susceptibility and heat capacity data indicated that NaPrTe$_2$ do not show long-range magnetic order or a spin-glass transition above 2$^\circ$ K.