Phase transitions of quartz studied by a.c. calorimetry

Abstract

An a.c. calorimetric heat capacity measurement has been performed on high-quality synthetic quartz. It was found that at the incommensurate (IC)-β-phase transition, the heat capacity C p of as-grown samples show critical behavior, i.e. there is a sharp peak at the IC-β transition. The shapes of the C p are almost identical in both heating and cooling runs. However, when as-grown samples were annealed in the α-phase just below the α-IC transition, the C p peak became considerably rounded and, at the same time, the transition temperature slightly increased. The shapes of the C p peaks on heating and cooling became dissimilar for the annealed samples.