DIELECTRIC-PROPERTIES OF SYNTHETIC QUARTZ CRYSTALS

The dielectric constant (K) and loss (tan delta ), hence the conductivity ( sigma ), of high-quality synthetic quartz crystals have been measured with the electric field parallel (or perpendicular) to the optical axis (c-axis). These measurements are carried out in the frequency region 10**2 to 10**7 Hz and in the temperature range 30 to 400 degree C. The temperature variation of K at different frequencies exhibits two regions: (i) a slow increase up to about 280 degree C which is frequency independent and (ii) a fast increase beyond 280 degree C which is frequency dependent, K having larger values at lower frequencies. Similar behaviour is exhibited by tan delta . Log sigma against 1/T plots show the usual extrinsic and intrinsic regions. The values for activation energy for conduction in the intrinsic region are calculated.