A NEW FAMILY OF FAST-ION CONDUCTOR-MONTMORILLONITES

The natural mineral montmorillonite is a type of aluminosilicate with a layered structure. Al-O and Mg-O octahedrons are sandwiched between layers of Si-O tetrapedral. The total conductivity of Li-montmorilloni te with 15% water content was determined by AC impedance measurement t o be 1.04 x 10(-3) S cm(-1) at 25 degrees C, and the activation energy is 0.13 eV. The conductivity of Na-montmorillonite with the same wate r content was determined to be 2.76 x 10(-3) S cm(-1); the activation energy is 0.11 eV. The results obtained with Ca-, Zn- and Mg-montmoril lonites with about 17% water content are 1.27 x 10(-3) S cm(-1), 1.02 x 10(-3) S cm(-1) and 1.21 x 10(-3) S cm(-1), respectively. The activa tion energies are all about 0.17 eV. By using Wagner's DC polarization technique, the electronic conductivities of Li- and Mg-montmorillonit es were measured to be 4 x 10(-10) S cm(-1) and 3 x 10(-10) S cm(-1). Their ionic conductivities measured here vary with the water content a nd are associated with outside surfaces. The compensated cations with their hydrated water spheres play the essential role in the conductivi ty.