Synthesis And Characterization Of Rare Earth Element Disilicates And Study Of The Morphology And Growth Mechanism Of Platinum Crystals

In the 21th century,there are more and more new materials and technologies. Silicates, metals and macromolecules are three kinds of basic man-made materials, and act as important roles in our life. Our research mainly concentrated on rare earth element (REE) disilicates and noble metal platinum.Disilicates, especially the REE disilicates REE₂Si₂O₇, have been widely studied for their unique magnetic, electrical and optical properties and their applications to optimize the properties of ceramic. Twelve different structure types (A-L, X) have been reported for the single rare earth element disilicates, which exhibit a complex structural chemistry under ambient conditions, due to largely the monotonic decrease in size of REE³⁺ cations through the lanthanide series. Based on synthesis of single disilcates, we tried to synthesize double REE disilicates. The crystals of B type structure of ErHoSi₂O₇ was synthesized under 1200℃and 2.0GPa using piston-cylinder apparatus. D type structure of ErHoSi₂O₇ was synthesized under1550℃using high temperature furnace. But the sizes of Er₂Si₂O₇ crystals are very small, they are not suitable for single crystal x-ray structure analysis. But we believe that through changing experimental conditions we will synthesized the larger single crystal of ErHoSi₂O₇.There has been considerable interest in platinum because of its unique properties and roles in industry. It is used in jewelry, to make crucible and special containers and as a catalyst. Single crystals of platinum were encountered as a by-conduct inhigh temperature synthesis of rare earth elements disilicates. The crystal structure of platinum was firstly refined from single-crystal X-ray diffraction at room temperature. The platinum single crystal crystallized in the cubic system with space group Fm-3m (no. 225) and with a = 3.925(17), Z = 4, R = 0.0478.The lattice of platinum is cubic face-centered and crystal structure is cubic close-packed. Pt atoms are regular twelvefold (bond distance = 2.775 A) coordination with the neighbor platinum atoms in this structure. From the SEM images of platinum crystals, we studied morphology and growth mechanism of platinum crystals.