A study of the electrodiffusion process in quartz

The electric current versus time curves which are observed during sweeping runs are investigated as possible indicators of the completeness of the electrodiffusion process in quartz. Both the growth of the Al-OH center and the decay of the Al-Na center with the sample current versus sweeping time were tracked. It is found that the current peak or plateau disappears when the sample is heated to 400°C and immediately cooled back to room temperature. No reduction in the Al-Na centers or production of the Al-OH centers match the disappearance of the peak. Instead, the Al-Na center is slowly replaced by the Al-OH after the sample has been held for some time at temperatures near 500°C. Since hydrogen is much less mobile than the alkalis, this replacement causes a reduction of the sweeping current. It appears that the appearance of a steady current during a time interval might be used as a signature for the completeness of the electrodiffusion process. It is found that when the current remains steady to ±2% over an eight to ten hour interval that the sample passes the OSU (Oklahoma State University) test for sweeping effectiveness. It does appear, however, that the tendency to form etch channels reduces more slowly than the rate of replacement of the alkalis at point defects