Thermal, structural and optical properties of un-doped and lanthanide-doped germanate ceramics.

In present work, thermal, structural and optical properties of un-doped Li 2 MgGeO 4 and lanthanide - doped Li 2 MgGeO 4 :Ln3+ (Ln = Er, Ho) germanate ceramics have been studied. Based on DSC measurements, two reversible phase transitions were verified during heating and cooling process of germanate ceramics. The results obtained from the Rietveld refinement indicate that Li 2 MgGeO 4 ceramics crystallize in monoclinic crystal lattice. Structural aspects were also evidenced by Raman and infrared spectroscopy. Emission investigations indicate that the most intense green bands due to the 4S 3/2 → 4I 15/2 (Er3+) and 5F 4 ,5S 2 → 5I 8 (Ho3+) transitions are well overlapped with broad band located near 500 nm. Broad green emission is attributed with the presence of magnesium in ceramic matrix. Based on literature data it can be assigned to F-type centers. • un-doped and lanthanide doped germanate ceramics have been studied. • Li 2 ZnGeO 4 ceramics crystallize in a monoclinic crystal lattice. • Intensive emission is due to 4S 3/2 → 4I 15/2 (Er3+) and 5F 4 ,5S 2 → 5I 8 (Ho3+) transitions. • Emission bands of Ln3+ are overlapped with broad green band of ceramic matrix. • Broad green emission is due to presence of magnesium and assigned to F-type centers. [ABSTRACT FROM AUTHOR]