Percolation effects in mixed β/β″-alumina crystals

Mixed β/β″-alumina crystals are two-dimensional ion conductors, whose conductivities vary dramatically upon mixing of two types of mobile ions. We summarize a theoretical model, which can explain these conductivity variations quantitatively. According to the model, percolation effects are expected to occur at intermediate mixing ratios and low temperatures. It is suggested that detailed measurements should uncover these effects and thus allow one to measure critical transport exponents predicted by percolation theory.