An investigation of the properties of large crystals of the zeolites dodecasil-3C and ferrierite by high-temperature birefringence microscopy and X-ray diffraction

Large crystals of two siliceous zeolites have been grown and studied as a function of temperature using bifrefringence microscopy. In one case organic template is retained and the crystals show a reversible, ferroelastic phase transition on heating and cooling, but in another the bifrefringence indicates migration of organic template to the crystal edges upon heating.

Observation of unusual temperature-dependent stripes in LiTaO₃ and LiTa_xNb_1-xO₃ crystals with near-zero birefringence

It is found that in LiTaO₃ crystals with compositions between congruent and stoichiometric and in mixed LiNb_xTa_1-xO₃ crystals self-organized stripes appear whose widths vary with temperature. They are broad and indistinct when the birefringence is close to zero and become narrower as the temperature is decreased or increased.

Evidence for a non-rhombohedral average structure in the lead-free piezoelectric material Na_0.5Bi_0.5TiO₃

The average structure of Na_0.5Bi_0.5TiO₃ was found to possess non-rhombohedral symmetry, as supported by the splitting of Bragg peaks in the high-resolution reciprocal space maps.