High-pressure, high-temperature equations of state using nanofabricated controlled-geometry Ni/SiO sub(2)/Ni double hot-plate samples

We have fabricated novel controlled-geometry samples for the laser-heated diamond-anvil cell (LHDAC) in which a transparent oxide layer (SiO sub(2)) is sandwiched between two laser-absorbing layers (Ni) in a single, cohesive sample. The samples were mass manufactured (>10 super(4) samples) using a combination of physical vapor deposition, photolithography, and wet and plasma etching. The double hot-plate arrangement of the samples, coupled with the chemical and spatial homogeneity of the laser-absorbing layers, addresses problems of spatial temperature heterogeneities encountered in previous studies where simple mechanical mixtures of transparent and opaque materials were used. Here we report thermal equations of state (EOS) for nickel to 100GPa and 3000K and stishovite to 50GPa and 2400K obtained using the LHDAC and in situ synchrotron X-ray microdiffraction. We discuss the inner core composition and the stagnation of subducted slabs in the mantle based on our refined thermal EOS. Key Points * Thermal equations of state for nickel and stishovite are presented * Nanofabrication techniques were used for novel sample synthesis * Nickel is denser than iron at core conditions beyond the molar mass differential