arXiv subjects

F. Chaimbault

Publications and source records attributed to F. Chaimbault.

3 recordsLinked to original sources

arXiv2005

Correlation between floppy to rigid transitions and non-Arrhenius conductivity in glasses

Non-Arrhenius behaviour and fast increase of the ionic conductivity is observed for a number of potassium silicate glasses $(1-x)SiO_2-xK_2O$ with potassium oxide concentration larger than a certain value $x=x_c=0.14$. Recovering of Arrhenius behaviour is provided by the annealing that enhances densification. Conductivity furthermore obeys a percolation law with the same critical concentration $x_c$. These various results are the manifestation of the floppy or rigid nature of the network and can be analyzed with constraint theory. They underscore the key role played by network rigidity for the understanding of conduction and saturation effects in glassy electrolytes.

cond-mat.dis-nn↗

arXiv2004

Direct evidence of rigidity loss and self-organisation in silicate glasses

The Brillouin elastic free energy change $DF$ between thermally annealed and quenched $(Na_2O)_x(SiO_2)_{1-x}$ glasses is found to decrease linearly at $x > 0.23$ (floppy phase), and to nearly vanish at $x < 0.18$ (stressed- rigid phase). The observed $D F(x)$ variation closely parallels the mean-field floppy mode fraction $f(x)$ in random networks, and fixes the two (floppy, stressed-rigid) elastic phases. In calorimetric measurements, the non-reversing enthalpy near $T_g$ is found to be large at $x < 0.18$ and at $x > 0.23$, but to nearly vanish in the $0.18 < x < 0.23$ range, suggesting existence of an intermediate phase between the floppy and stressed-rigid phases.

cond-mat.mtrl-sci↗

arXiv2003

Percolative conductivity in alkaline earth silicate melts and glasses

Ion conducting $(CaO)_x(SiO_2)_{1-x}$ glasses and melts show a threshold behaviour in dc conductivity near $x=x_t=0.50$, with conductivities increasing linearly at $x>x_t$. We show that the behaviour can be traced to a rigid ($x<0.50$) to floppy ($x>0.50$) elastic phase transition near $x=x_t$. In the floppy phase, conductivity enhancement is traced to increased mobility or diffusion of $Ca^{2+}$ carriers as the modified network elastically softens.

cond-mat.mtrl-sci↗