. Absorption peak at 3580 cm1 corresponds to OH groups.
In the case of α-quartz crystal we performed heating of the sample
at 550 °C (just below α–β transition) and also at 660 °C. We get
remarkable changes in IR absorption presented in Fig. 1 already
with heating to 550 °C. The part of sample doped with phosphorus
becomes opalescence. We did not find procedure completely
restoring sample properties.