title: Garnet-to-perovskite transition in Gd3Sc2Ga3O12 at high pressure and high temperature.
abstract: The structural phase transition of gadolinium-scandium-gallium garnet (Gd(3)Sc(2)Ga(3)O(12), GSGG) has been studied at high pressure and high temperature using the synchrotron X-ray diffraction technique in a laser-heated diamond anvil cell. The GSGG garnet transformed to an orthorhombic perovskite structure at approximately 24 GPa after laser heating to 1500-2000 K. The garnet-to-perovskite phase transition is associated with an ∼8% volume reduction and an increase in the coordination number of the Ga(3+) or Sc(3+) ion. The orthorhombic perovskite GSGG has bulk modulus B(0) = 194(15) GPa with B(0)' = 5.3(8), exhibiting slightly less compression than the cubic garnet structure of GSGG with B(0) = 157(15) GPa and B(0)' = 6.5(10). Upon compression at room temperature, the cubic GSGG garnet became amorphous at ∼65 GPa. Coupled with the amorphous-to-perovskite phase transition in Y(3)Fe(5)O(12) and Gd(3)Ga(5)O(12) at high-pressure-temperature conditions, we conclude that amorphization should represent a new thermodynamic state resulting from hindrance of the garnet-to-perovskite phase transition, whereas the garnet-to-amorphous transition in rare-earth garnets should be kinetically hindered at room temperature.
authors.affiliation: Beijing Synchrotron Radiation Facility (BSRF), Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Chuanlong
authors.initials: C
authors.lastname: Lin
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.forename: Jung-Fu
authors.initials: JF
authors.lastname: Lin
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Li
authors.forename: Yanchun
authors.initials: Y
authors.lastname: Li
authors.forename: Qingli
authors.initials: Q
authors.lastname: Zhang
authors.forename: Lun
authors.initials: L
authors.lastname: Xiong
authors.forename: Rui
authors.initials: R
authors.lastname: Li