Eu3+ as a probe for rare-earth dopant site structure in nano-glass-ceramics

Eu3+-doped transparent nano-glass-ceramics, 32(SiO2)9(AlO1.5)31.5(CdF2)18.5(PbF2)5.5(ZnF2):3.5(EuF3)mol %, have been prepared aiming at the investigation of the site structure of the Eu3+ rare-earth dopant. In this nano-glass-ceramic host, other rare-earth dopants, such as Er3+, Tm3+, Ho3+, and Dy3+, also have served as a dopant; however the Eu3+ ion is a preferably sensitive probe for a rare-earth dopant site structure due to its unique purely magnetic and purely electric dipole moment optical transitions involving the nondegenerate excited D-5(0) and ground F-7(0) states. The splitting in the respective emission and absorption spectra in the crystalline field of the nano-glass-ceramics and its parent glass has been studied. It has been concluded that the major site of the rare-earth dopant in the nano-glass-ceramics is nearly cubic, with an orthorhombic distortion according to the sequence O-h -> D-4h -> D-2h, and the majority of the rare-earth dopants substitute onto the Pb2+ site in the PbF2 nanocrystals embedded in the glass network. A vibronic contribution to the strength of the D-5(0)-> F-7(2) electric dipole moment transition has been found and the respective dominating contributing vibration mode has been proposed to be and to change as a(2u)-> b(1u)-> a(u), according to lowering the site symmetry in a sequence O-h -> D-4h -> D-2h. (c) 2007 American Institute of Physics.