Lanthanide tantalite (Ln= La, Nd, Sm, Dy, Er and Tm) was synthesized by a solid state reaction between mixed powders of and . The single-phase was prepared by sintering at temperatures of 1423-1673 K in air. The SEM observation showed that the particles were provided with the growth steps and the depeloped facets. The photocatalytic activity for water splitting of prepared was measured under UV light irradiation. The activity obtained was higher than that previously reported. These results suggested the crystallinity of photocatalysts correlates closely with the efficiency of water splitting.

The preparation of single-phase with delafossite-type structure by means of the solid-state reaction method was investigated using X-ray diffraction. The results showed that notwhistanding the fact that there was a trace of metallic copper, nearly single-phase was obtained by using as a lanthanum source and by firing the mixed powder with nonstoichiometric composition ratio of in a vacuum at 1273 K for 10 h. The measurement of electrical conductivity and Seebeck coefficient showed that thus obtained was a p-type semiconductor and had a Seebeck coefficient of approximately .