Hydrothermal synthesis quartz samples which doped the impurity ions (Ge^<4+>, Al^<3+>, B^<3+>, Na^+) were prepared. The effect of impurity ions on crystallite size, specific heat capacity, and phase transition temperature were examined. With the increase in the defect concentration, the following were observed: (1) the refinement of crystallite size, (2) the increase in specific heat capacity, (3) the fall in α→β phase transition beginning temperature Thb on heating, (4) the rise in β→α phase transition beginning temperature Tcb on cooling, and (5) the increase in the difference between α→β and β→α phase transition temperature ΔTb (= Tcb - Thb). These results were fundamentally equal to the plane defect generation quartz sample reported previously. However, the effect for these results was greatly different by the type of ion. The non-cross-link oxygen formation ion (Na^+) made the α→β phase transition temperature greatly fall, and the isomorphous substitution type ions (Al^<3+>, Ge^<4+>) made the β→α phase transition temperature greatly rise. B^<3+> ion showed the medium property of both ion groups. The defect formed by the non-cross-link oxygen and the isomorphous substitution respectively was considered to contribute as an active site of α→β phase transition. The combination of the transition temperatures on heating and cooling obtained from both the standard quartz and impurities doped quartz was effective to express the characteristic of the defect They were the values that were (1) the difference (ΔThb=Thb_<[sample]> - ΔThb_<[standard]>, ΔTcb=Tcb_<[sample]>- ΔTcb_<[standard]>) of the temperature of both, (2) (1) their ratio (|ΔThb-ΔThb|) and (3) the difference (ΔTb=Tcb- Thb) of the temperature for each sample.
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