PHYSICAL-PROPERTIES OF RARE-EARTH METAL-ION VERMICULITE INTERCALATION COMPOUNDS

The structural and magnetic properties of vermiculite intercalation compounds (VIC's) with two-water-layer hydration states having Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, and Er3+ ions in the interlamellar space between the host silicate layers have been studied by means of (00L) x-ray scattering, dc magnetic susceptibility, and thermogravimetric measurements. The intercalate layer sandwiched between two water layers consists of u cations and w water molecules per unit rectangular cell of (a X b): u = 0.5-0.69, w = 0-4.0. The c-axis repeat distance is found to be roughly proportional to the ionic radius, giving indirect evidence for the strong rigidity of the host silicate layers. The magnetic susceptibility of these compounds shows a Curie-Weiss behavior. The Curie-Weiss temperature THETA for Ce3+, Pr3+, Nd3+, and Sm3+ is described by THETA = -1.58J(J + 1) [K], while THETA for Gd3+, Tb3+, Dy3+, Ho3+, and Er3+ is described by THETA = 0.93(g(J) -1)2J (J + 1) [K]. The Eu3+ VIC shows a Van Vleck susceptibility in the temperature range between 50 and 300 K.