Synthesis, Growth And Characterization Of Phospho-silicides

Phospho-silicides are important functional materials with a variety of crystal structures. There are severial very famous phospho-silicides with semiconductor properties, magnetic properties, or nonlinear optical properties, such as CdSiP2, ZnSiP2, FeSi4P4, and other Rare-earth phosphor-silicides.Among them, CdSiP2crystal is one of new nonlinear optical crytals with very excellent properties, such as high nonlinear optical coefficients (d14=84.5pm/V), broad transmittance in mid-infrared range (0.5-10μm), high thermal conductivity, and high chemical stability. The first large CdSiP2singel crystal was grown by BAE systems in2010. Our group reported the crystal growth of CdSiP2by Bridgman method.Rare researches have been paid on the compounds of FeSi4P4, LaSi2P6and LaSiP3. In this paper, we reported the polycrystalline synthesis and the crystal growth of the FeSiP4compound. High temperature solid state method and metal flux method have been used to synthesis the crystalline FeSi4P4and to grow the large FeSi4P4crystal, respectively, and the basic properties were studied. The metal flux method has also been used to growth NdSiP3and NdSi2P6and their crystal structures were determined. The main contents are as fellows:1. Synthesis and crystal growth of CdSiP2The reaction processes of CdSiP2polycrystalline have been analysed by measuring the content of the products in different temperature At the same time, the effect of the crucible materials on the polycrystalline synthesis were also studied. The results show that PBN crucible is more favor for the high quality polycrystalline CdSiP2synthesis The CdSiP2crystals were grown by vertical Bridgman-Stockbarger method, but the quality of CdSiP2was too bad for the orientation and characterization of CdSiP2crystal. 2. Synthesis and crystal growth of the FeSi4P4The preparation of polycrystalline FeSP4was conducted by the high temperature solid state method in two ways. The one way:the FeSi4P4polycrystalline was synthesized from the stoichiometric amounts of high purity Fe, Si, and red P starting materials by solid state method, and the process of synthesis was studied. The other way:the FeSi4P4polycrystalline was synthesized from the stoichiometric amounts of FeP2, Si and P starting materials, and the process of synthesis was studied. The result shows that the first way failed because of the vapour pressure of P in the high temperature. The other way shows that the product include the FeSi4P4polycrystalline and with some impurity. So the high temperature solid state method cannot be used to synthesis the high purity FeSi4P4polycrystalline. The large crystal of FeSi4P4was grown by the metal flux method and some of its properties were studied.3. Crystal growth and crystal structure of NdSiP3and NdSi2P6The crystal growth of the NdSiP3and NdSi2P6was studied by two ways. The first way:the NdSiP3and NdSi2P6crystals were grown using Nd, Si, and P as starting materials and the flux was Sn. The other way:we grown the crystals of NdSiP3and NdSi2P6using the Nd, Fe, Si, P as starting materials and the metal Sn as flux. The crystal structure was determined by the single crystal diffractometer.