Investigations on vanadyl doped ARbB4O7 (A=Li, Na, K) glasses by EPR and optical studies

EPR and optical absorption investigations are carried out at room temperature on vanadyl doped ARbB4O7 (A=Li, Na, K) glasses. These results indicate that the VO2+ ion enters the glass matrix into a tetragonally compressed octahedral site. The spin-Hamiltonian parameters calculated from the EPR spectra for the three glass systems LRB, NRB and KRB are: gparallel=1.948, gorthogonal=1.976, Aparallel=157x10-4, Aorthogonal=58x10-4cm-1; gparallel=1.948, gorthogonal=1.977, Aparallel=157x10-4, Aorthogonal58x10-4cm-1 and gparallel=1.948, gorthogonal=1.979, Aparallel=157x10-4, Aorthogonal59x10-4cm-1, respectively. The optical spectrum exhibits three characteristic bands for all these glasses suggesting C4v symmetry. The crystal field and tetragonal field parameters evaluated using the optical data for the three systems LRB, NRB and KRB are: Dq=1666, Ds=-3339, Dt=450cm-1; Dq=1666, Ds=-3329, Dt=441cm-1 and Dq=1666, Ds=-3219 and Dt=507cm-1, respectively. The bonding parameters indicate a moderately covalent bond between the metal ions and ligands