The high-temperature mechanical behavior of zircon materials may be connected with the chemical nature of the glassy phase present in these materials. Internal-friction measurements were carried out with a low-frequency pendulum, working in the 300 to 1300 K temperature range. The samples were zircon materials fabricated by sintering at 1843 K (ZIsamples) and 1903 K (ZII samples).
In the ZII samples, a mechanical loss peak is observed in the temperature range between 1000 and 1250 K; the peak temperature depends on the frequency of measurement. This peak is tentatively attributed to grain boundary sliding controlled by the viscosity of the glassy phase segregated in the boundary, in the temperature range of its α relaxation.