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Na2TiGeO5: Crystal structure stability at low temperature and high pressure

“…Single crystals of Na 2 TiGeO 5 were grown by the flux method, the crystallization process being described in detail by Kireev et al [6]. The evolution of the unit-cell parameters with temperature was measured from room temperature down to 120 K using a Huber 4-circle diffractometer at station D3 of the synchrotron radiation facility HASYLAB-DESY in Hamburg, Germany.…”

“…The latter is important in geophysical science [1][2][3][4][5]. The isostructural compound Li 2 TiGeO 5 (LTGO) exhibits interesting physical properties such as ionic conductivity and a structural phase transition of ferroelastic nature [6]. Ferroelastics are currently the subject of various studies, because they can be widely used in acousto-optic and acousto-electric devices [7].…”

“…The structure is built of layers of TiO 5 square pyramids sharing corners with the MO 4 tetrahedra [1][2][3][4][5][6]. Polyhedral layers, forming an open framework, alternate with layers of alkali ions (Fig.…”

“…The distinctive Ti V coordination with one short titanyl bond suggests that some of these compounds may be useful as nonlinear optical materials. Several experiments have been performed to shed light on the mechanism of the ionic transport of the natisites, since this phenomenon is important in solid electrolytes for fuel cells and ionselective membranes [6]. Strong anisotropy was observed for sodium and lithium germanates.…”

“…Strong anisotropy was observed for sodium and lithium germanates. The preferred direc- tion of ion transport at 400 K is in the ab plane of the unit cell, where the conductivity is three orders of magnitude larger than that in the perpendicular direction along the caxis [6]. This fact has led to questions about the role of the alkali cation size and cation vacancies in ionic migration.…”