Percolative conductivity in alkaline-earth silicate melts and glasses

Ion-conducting (CaO)x(SiO2)1 − x glasses and melts show a threshold behaviour in dc conductivity near x = xt = 0.50, with conductivities increasing linearly at x > xt. We show that the behaviour can be traced to a rigid (x 0.50) elastic phase transition near x = xt. In the floppy phase, conductivity enhancement is traced to increased mobility or diffusion of Ca2+ carriers as the modified network elastically softens.