Crystal growth and structure of three new neodymium containing silicates: Na_(0.50)Nd_(4.50)(SiO_4)_3O, Na_(0.63)Nd_(4.37)(SiO_4)_3O_(0.74)F_(0.26) and Na_(4.74)Nd_(4.26)(O_(0.52)F_(0.48))[SiO_4]_4

摘要

Single crystals of Na_(0.50)Nd_(4.50)(SiO_2)_3O, Na_(0.63)Nd_(4.37)(SiO_4)_3O_(0.74)F_(0.26) and Na_(4.74)Nd_(4.26)(O_(0.52_F_(0.48))[SiO_4]_4 were synthesized via flux growth using a NaF/KF eutectic flux and the crystal structure was determined by single crystal X-ray diffraction. Na_(0.50)Nd_(4.50)(SiO_4)_3O and Na_(0.63)Nd_(4.37)(SiO_4)_3O_(0.74)F_(0.26) adopt the apatite structure and crystallize in the hexagonal space group P6_3/m, while Na_(4.74)Nd_(4.26)(O_(0.52)F_(0.48))[SiO_4]_4 crystallizes in the tetragonal space group I-4 and exhibits rare-earth mixing on the sodium site. The unit cells of the crystals are a = 9.5400(3) A and c = 7.0331(5) A for Na_(0.50)Nd_(4.50)(SiO_4)_3O, a = 9.5533(3) A and c = 7.0510(4) A for Na_(0.63)Nd_(4.37)(SiO_4)_3O_(0.74)F_(0.26), and a = 12.1255(3) A and c = 5.4656(2) A for Na_(4.74)N-d_(4.26)(O_(0.52)F_(0.48))[SiO_4]_4. These three compounds exhibit three-dimensional crystal structures that are discussed in detail in this paper.