Angular and polarization properties of light scattering at the α–β phase transition of quartz

When α- and β-phases coexist in a single crystal of quartz two different kinds of light scattering are observed in two adjacent boundary regions between the α- and β-phases. Their intensity variations as a function of the modulus of the scattering vector ∣Δk∣ and their polarization properties are measured. In the region near the β-phase, small angle scattering is observed with an intensity varying as ∣Δk∣−3 and always with the same polarization as the incident light. In an adjacent region near the α-phase the variation of the scattered intensity as a function of ∣Δk∣ is weaker so that scattering at large angles is observed (for some crystal orientations this large angle scattering is depolarized). The small angle scattering probably results from a mixing of α- and β-phases while the large angle scattering may be related to Dauphiné twinning of α-phase.