Heat Capacity in α-β Phase Transition of Quartz

The heat capacity ( C p ) of quartz was measured by AC calorimetry near the α-β phase transition temperature. The existence of the intermediate phase (IP) was confirmed. A sharp increase of C p was observed at T C , the lower transition temperature. The value of T C in heating runs (HR) was higher than that in cooling runs (CR) by about 0.9 K. A hump of C p was clearly observed at T Q , the higher transition temperature in CR and also in HR of a special heating cycle without passing through T C . It was obscure, however, in the ordinary HR because of the hysteresis. The temperature range of IP was 1.15±0.05 K in CR, which is significantly narrower than the range where the X-ray satellite reflections are observable.