Glass in Two Forms: Heterogeneous Electrical Relaxation in Nanoglassy Petalite

Glassy materials with specific functions are almost universally used in our daily life. If prepared via quenching, that is, by rapid cooling of the molten glass, a frozen liquid with a high degree of lattice disorder and stress is obtained. The release of stress through mechanical action may significantly affect the microstructure and dynamic features of the so-obtained nanoglass. Considering ion conducting glasses, it has recently been shown that mechanical treatment of glasses causes the long-range ion transport to significantly decrease. The origin of this astonishing behavior of nanoglasses is, however, far from being understood completely. Here, we show that depending on the duration of mechanical impact in a high-energy planetary ball mill, the petalite glass, LiAlSi ₄ O ₁₀ , passes through a state with two Li reservoirs distinctly differing in electrical relaxation and, thus, in ion transport. The two species, characterized by electrical relaxation rates differing by two orders of magnitude, show up clearly if we use the electric modulus representation to analyze the data. This feature is also seen in conductivity spectra revealing a two-step increase of the conductivity with frequency. Accordingly, we propose a two-phase model with nanometer-sized non-relaxed glassy particles next to or surrounded by structurally relaxed regions.