A new method for determining the d.c. conductivity of powdered materials

The measurement of d.c. ionic conductivity in samples that are not liquids or monolithic solids generally presents a problem. Here we show how the d.c. ionic conductivity determined for a powdered glass can reproduce the conductivity of the monolithic material using a.c. measurements on a sample contained in a sealed NMR tube, in which the structural characteristics can be sequentially determined. While the technique we have developed here has been proof tested and verified against d.c. ionic conductivity measurements made on bulk pieces of Li+ ion conducting glasses, the methodology we have developed should be valid for both crystalline and amorphous samples. The tremendous advantage that this technique presents is that it obviates the need to produce pressed pellets of powders under study and in doing so completely avoids the often very difficult and time consuming process of curve fitting the, typically, complicated and convoluted complex impedance plane arcs to separately determine the bulk and intergranular grain boundary impedances.