6533b855fe1ef96bd12b0634

RESEARCH PRODUCT

Post-spinel transformations and equation of state inZnGa2O4: Determination at high pressure byin situx-ray diffraction

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Room-temperature angle-dispersive x-ray diffraction measurements on spinel ZnGa{sub 2}O{sub 4} up to 56 GPa show evidence of two structural phase transformations. At 31.2 GPa, ZnGa{sub 2}O{sub 4} undergoes a transition from the cubic spinel structure to a tetragonal spinel structure similar to that of ZnMn{sub 2}O{sub 4}. At 55 GPa, a second transition to the orthorhombic marokite structure (CaMn{sub 2}O{sub 4}-type) takes place. The equation of state of cubic spinel ZnGa{sub 2}O{sub 4} is determined: V{sub 0} = 580.1(9) {angstrom}{sup 3}, B{sub 0} = 233(8) GPa, B'{sub 0} = 8.3(4), and B''{sub 0} = -0.1145 GPa{sup -1} (implied value); showing that ZnGa{sub 2}O{sub 4} is one of the less compressible spinels studied to date. For the tetragonal structure an equation of state is also determined: V{sub 0} = 287.8(9) {angstrom}{sup 3}, B{sub 0} = 257(11) GPa, B'{sub 0} = 7.5(6), and B''{sub 0} = -0.0764 GPa{sup -1} (implied value). The reported structural sequence coincides with that found in NiMn{sub 2}O{sub 4} and MgMn{sub 2}O{sub 4}.