TY - JOUR

T1 - Topologically prone or cation compression restricted phase transition: an example of feldspar-related SrGe2B2O8

AU - Gorelova, Liudmila

AU - Khandarkhaeva, Sayana

AU - Yukhno, Valentina

AU - Krzhizhanovskaya, Maria

AU - Vereshchagin, Oleg

AU - Dubrovinsky, Leonid S.

PY - 2023/3

Y1 - 2023/3

N2 - The stability and phase transformation processes of SrGe2B2O8 were studied under extreme conditions (up to 960 ºC / 40 GPa) using in situ single-crystal and powder X-ray diffraction. The compound demonstrated stability up to 900 °C, when it starts to decompose to SrGe4O9 and Sr2B2Ge4O14. Under high-pressure (HP) conditions SrGe2B2O8 undergoes two phase transitions, accompanied by formation of B2O7 dimers and stepwise increasing of Ge coordination number from 4 to 6 through the 5-coordinated polyhedron. This unusual stepwise increase in the coordination number of the framework cation is consistent with the behavior of silicon in isostructural CaSi2B2O8, suggesting that certain topologies are prone to similar effects. We also assume that observed differences in HP behavior of isostructural paracelsian-like phases is caused by different compression capacities of tetrahedral cations (Si, Al, B).

AB - The stability and phase transformation processes of SrGe2B2O8 were studied under extreme conditions (up to 960 ºC / 40 GPa) using in situ single-crystal and powder X-ray diffraction. The compound demonstrated stability up to 900 °C, when it starts to decompose to SrGe4O9 and Sr2B2Ge4O14. Under high-pressure (HP) conditions SrGe2B2O8 undergoes two phase transitions, accompanied by formation of B2O7 dimers and stepwise increasing of Ge coordination number from 4 to 6 through the 5-coordinated polyhedron. This unusual stepwise increase in the coordination number of the framework cation is consistent with the behavior of silicon in isostructural CaSi2B2O8, suggesting that certain topologies are prone to similar effects. We also assume that observed differences in HP behavior of isostructural paracelsian-like phases is caused by different compression capacities of tetrahedral cations (Si, Al, B).

KW - SrGe2B2O8

KW - feldspar

KW - paracelsian

KW - danburite

KW - high-pressure

KW - high-temperature

KW - SrGe2B2O8Feldspar

KW - paracelsian

KW - danburite

KW - high-pressure

KW - high-temperature

UR - https://www.sciencedirect.com/science/article/pii/S0925838822050332

M3 - Article

JO - Journal of Alloys and Compounds

JF - Journal of Alloys and Compounds

SN - 0925-8388

M1 - 168642

ER -