Pressure Effects on the Size of Type‑I and Type-II Si-Clathrates Synthesized by Spark Plasma Sintering
datasetposted on 02.01.2013, 00:00 by S. Stefanoski, M. C. Blosser, G. S. Nolas
The crystallinity of clathrate-I Na8Si46 and clathrate-II Na24Si136 was investigated as a function of applied pressure and temperature employing spark plasma sintering. Na8Si46 and Na24Si136 with full Na and Si occupancies were obtained at 450 and 600 °C, respectively. Microcrystalline powders were obtained at 60 MPa, and single crystals were obtained at 100 MPa. The size of the crystals increased with pressure for the clathrate-II Na24Si136, while a threshold value in pressure separated microcrystalline and single-crystal clathrate-I Na8Si46.