Synthesis and characterization of Er(III) and Y(III) sodium silicates:: Na3ErSi3O9, a new infrared emitter

The hydrothermal synthesis in mild conditions, and the structural characterizations and luminescence properties, of yttrium and erbium silicates Na3MSi3O9, M = Y(III) and Er(III), has been reported. Na3ErSi3O9 is a new infrared emitter with an emission spectrum displaying a broad visible band (300-700 nm) and a series of narrow infrared intra-4f(11) I-4(13/2) --> I-4(15/2) lines. The number of Stark components detected (ca. 32) indicates the presence of four optically active environments, in accord with the structural data. When the temperature is raised from 14 to 300 K, the I-4(13/2) --> I-4(15/2) transition integrated intensity increases by a factor of ca. 3.7. This remarkable and unusual behavior is the opposite temperature dependence usually observed for silicon-based materials. The samples' structures have been characterized by SEM, powder XRD, Si-29 MAS NMR, and Na-23 single- and multiple-quantum (MQ) MAS NMR. Using the recently introduced MQ MAS NMR FAM II (fast amplitude modulation of radio frequency pulses) technique, it has been possible to observe all 12 nonequivalent Na atoms in Na3YSi3O9, even those with large quadrupole coupling constants (in excess of 4 MHz).