中国科学院地球化学研究所机构知识库

Studying manganese fluoride (MnF2) under high-pressure and high-temperature (HP-HT) conditions is of great significance for understanding its important magnetic and piezomagnetic properties. The structural evolution and thermoelastic behavior of MnF2were studied at HP-HT conditions up to ∼13.1 GPa and∼700 K based on in situ synchrotron angle dispersive powder x-ray diffraction (XRD) combined with diamond anvil cell (DAC). Four phases of MnF2 are successfully observed through the pressure-temperature (P-T)range of the experiment. The structural phase transitions are with the following sequence: rutile-type (P42/mnm) → α-PbO2-type (Pbcn) → P42m → ZrO2-type (Pbcm) → SrI2-type (Pbca) at HP-HT conditions, where theα-PbO2-type (Pbcn) and the P42m structures are observed upon decompression. A phase diagram of MnF2 is presented in this study. In addition, the bulk modulus for the SrI2-type structure (Pbca) of MnF2 is 84 (3)GPa when fixed K0′ = 4. Moreover, we also obtain (∂K/∂T)P = −0.012 (7)GPaK−1 , and the volumetric thermal expansion coefficient α0 = 3.8 (7) × 10−5 K−1 at 300 K. Furthermore, the thermal expansion coefficients for the rutile-type structure (P42/mnm) of MnF2 by fitting the temperature-volume data to the Fei-type thermal equation of state (EoS) are also obtained. The volumetric thermal expansion coefficient of MnF2 is 0.87 × 10−5 K−1 , and its axial thermal expansivities are αa0 = 0.13 × 10−5 K−1 and αc0 = 0.64 × 10−5 K−1 along the a-axis and c-axis, respectively.