高純度二酸化ケイ素試薬を用いた石英の合成と不純物ドープ実験

Abstract

Several quartz samples containing one or two impurities were synthesized under the ambient pressure and the hydrothermal conditions by using the starting materials prepared from high purity silicon dioxide and silicon tetraethoxide. Phase transition from cristobalite to quartz occurred in the cases of coexistence of Li ion with the concentration of which are above 600 ppm under the ambient and above 50 ppm under the 100 MPa pressure. Although impurity elements usually detected in natural quartz can be doped into in the lattice in a couple with Li, cations with larger ionic radius such as Ca and K ions did not enter at ambient pressure. Under the hydrothermal condition, almost cations can be doped into the lattice as a single dopant. Such incorporated impurities to synthetic quartz were confirmed by ESR, X-ray diffraction measurement and thermal neutron irradiation. Unit cell volume of the doped quartz shows unique variation with the ionic radius of impurity ions. Lattice strain estimated from X-ray diffraction peak profiles around 90 Bragg angle (2θ) was very sensitive to the content of dopant. ESR signals showed that there exist trace Al, Na and Li in synthetic quartz made of 99.999% reagent.