氧化镍（绿镍矿）等温压缩及高压相变研究

 本文采用DAC（金刚石压砧高压腔）装置，对氧化镍进行了静水压、非静水压、电导率测量等系统高压实验，获取了氧化镍等温压缩、高压相变及电导率压力效应的新结果，并在实验数据的基础上，对其高压相变与电性及磁性变化关系及体弹性模量作了分析讨论。

ISOTHERMAL COMPRESSION AND HIGH PRESSURE PHASE TRANSFORMATION OF NICKEL OXIDE (BUNSENITE)

Nickel oxide (NiO, Bunsenite) has been used as an analogue modeling composition in relation to other monoxide as MgO, FeO of earth interior. Crystal structure change of NiO from NaCl type fcc to rhombohedral was discovered by Rooksby in 1943 at low temperature—183 ℃. We recently carried out experiments under high pressure to 12.0 GPa using diamond anvil cell with liquid pressure transmitting medium and direct compression to 29 GPa. Our experimental results show the isothermal compression of NiO under pressure from 1.22 GPa to 8.87 GPa, lattice parameters and molal volume. At zero pressure: a₀=0.418 24 nm; V_m=11.009 9×10^-3 nm³; density, 6.780 2 g/cm³ and at 8.87 GPa; a=0.411 39 nm; V_m=10.481 9×10^-3 nm³; density, 7.125 4 g/cm³. All data show a small deviation from Drickamer and S. K. Agrawal’s results. The diffraction lines (111), (220) of NiO suddenly splitting until pressure loading up to 12 GPa at hydrostatic compression. Phase change of NiO from cubic to rhombohedral. The same results obtained by direct compression at pressure to 5.8 GPa and up to 29 GPa. Lattice parameter of rhomb, new phase a=0.296 70 nm; c=0.700 00 nm; V_m=10.708 4×10^-3 nm³; density, 6.972 6 g/cm³, this date agree with Rooksby's a=0.296 60 nm. The magnetic properties of NiO vary with pressure change Neel temperature of NiO 250 ℃ (523 K), decreases, when pressure increases, whereas below Neel temperature NiO changed in antiferromagnetic and rhombohedral crystal structure. Calculation bulk modulus of NiO by Birch-Manghnahan equation best fits to the p-V data and assuming K₀' values of 4, give K₀=166.83 GPa. Molal volume vs bulk modulus shows the compressibility of NiO is approaching to MgO.