Crystal growth, structure determination, and optical properties of new potassium-rare-earth silicates K3RESi2O7 (RE = Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)

摘要

Single crystals of K3RESi2O7 (RE= Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were grown from a potassium fluoride flux. Two different structure types were found for this series. Silicates containing the larger rare earths, RE= Gd, Tb, Dy, Ho, Er, Tm, Yb crystallize in a structure K3RESi2O7 that contains the rare-earth cation in both a slightly distorted octahedral and an ideal trigonal prismatic coordination environment, while in K3LuSi2O7, containing the smallest of the rare earths, lutetium is found solely in an octahedral coordination environment. The structure of K3LuSi2O7 crystallizes in space group P6(3)/mmc with a = 5.71160(10) Angstrom and c= 13.8883(6),Angstrom. The structures containing the remaining rare earths crystallize in the space group P6(3)/mcm with the lattice parameters of a = 9.9359(2),Angstrom, c = 14.4295(4) Angstrom, (K3GdSi2O7)a = 9.88730(10),Angstrom, c = 14.3856(3) Angstrom, (K3TbSi2O7) a = 9.8673(2) Angstrom, c = 14.3572(4),Angstrom,. (K3DySi2O7 a = 9.8408(3),Angstrom, c = 14.3206(6) Angstrom, (K,HoSi2O7) a = 9.82120(10) Angstrom, c = 14.2986(2),Angstrom, (K3ErSi2O7) a = 9.80200(10) Angstrom, c = 14.2863(4),Angstrom, (K3TmSi2O7) a = 9.78190(10),Angstrom, c = 14.2401(3),Angstrom, (K3YbSi2O7). The optical properties of the silicates were investigated and K3TbSi2O7 was found to fluoresce in the visible. (C) 2002 Elsevier Science (USA). All rights reserved. [References: 25]