Ca3Co2O6 crystal has a K4CdCl6-derived structure with a space group of R 3c, characterized by the two-different Co sites; an octahedral site (Co1) and a trigonal prism site (Co2), which alternately stand along a hexagonal c-axis in an infinite Co2O6 chain. 1) The Co–O bond length 1.916 A of Co1 is appreciably smaller than the Co–O bond 2.062 A of Co2. This indicates that the Co1 site is in a low-spin (LS) state under the influence of strong crystalline field while the Co2 site is in a high-spin (HS) state. The magnetic moments for Co1 and Co2 were estimated from the powder neutron diffraction to be 0:08 0:04 B and 3:00 0:05 B, respectively. The anisotropic magnetization measurements and their analysis have suggested the tri-valent of Co ions for both Co1 and Co2 sites. The interaction in each chain along c-axis is ferromagnetic and a partially disordered antiferromagnetic state appears by the interchain antiferromagnetic interaction, which brings in a spin freezing at low temperatures due to magnetic frustration in the triangular lattice. Although there are plenty of reports on substituted systems for cobalt sites of Ca3Co2O6, there are no experimental studies on the substitution for Ca sites of Ca3Co2O6 except for the band calculation of the Ysubstituted Ca3Co2O6, in which the ferromagnetic insulator at specific Y concentrations has been predicted. We consider that substitution for Ca site has the advantage of investigating the valence and spin-states of Co ions of Ca3Co2O6 because the randomness in the Co sites is not relevant at all. In this short-note, we report the first systematic studies of lattice parameters, magnetic susceptibility, and electrical resistance for polycrystalline samples of Ca3 xYxCo2O6. Polycrystalline samples of Ca3 xYxCo2O6 (x 1⁄4 0:0, 0.1, 0.2, 0.5) were prepared by a solid-state reaction. CaCO3, Co3O4, and Y2O3 were dehydrated at 200 C for one night, mixed with a cationic composition of (Ca,Y) : Co 1⁄4 3 : 2:1 for 1 h, pressed into pellets, and heated in air atmosphere at 980 C for 48 h. Samples were checked to be single phase from the powder X-ray diffraction. Magnetic susceptibility was measured by using a standard Faraday type magnetometer (Cahn-2000) in a magnetic field of 0.81 T from 4.2 to 300K. Electrical resistance measurements were carried out using a conventional four-probe method from 300K down to the lowest temperature where the resistance was not beyond a few tens of megaohms. Lattice parameters of Ca3 xYxCo2O6 (x 1⁄4 0:0, 0.1, 0.2, 0.5) are summarized in Table I. With increasing x, the hexagonal c-axis along an infinite Co2O6 chain increases monotonically while the a-axis is not altered appreciably. It is noted that the c=a ratio determines the relative strengths of interchain and intrachain coupling. Figure 1 shows the temperature dependence of magnetic susceptibility for Ca3 xYxCo2O6. For x 1⁄4 0:0, 0.1, and 0.2, the onset temperature T1 of a steep rise in susceptibility and the peak temperature T2 correspond to the ferromagnetic and the partially disordered antiferromagnetic transition temperatures, respectively. As shown in the inset of Fig. 1, both T1 and T2 shift to lower temperature with increasing x and finally disappear at x 1⁄4 0:5 at temperatures above 4.2K. The x dependence of T1 implies that the expansion of Co–Co distance suppresses the intrachain ferromagnetic interaction. In this respect, Martinez et al. reported that the ferrimagnetic phase, resulting from the antiferromagnetic coupling of ferromagnetic chains, is stabilized under pressure. Therefore, the x-dependence of T2 can be qualitatively interpreted as the negative pressure effect due to the volume expansion by the doping. The susceptibility data were fitted to the Curie–Weiss law between 100 and 300K. The magnetic parameters obtained from the least-squares fitting are listed in Table I, where eff is an effective magnetic moment, is a Curie–Weiss temperature, and 0 is a temperature-independent susceptiTable I. Lattice parameters, magnetic parameters obtained from Curie– Weiss fitting, and activation energy estimated from resistance measurements in Ca3 xYxCo2O6 (x 1⁄4 0:0, 0.1, 0.2, 0.5).