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

Synthesis and photoluminescent characterization of ceramic phosphors Li2MgGeO4:Ln3+ (Ln3+ = Pr3+ or Tm3+) under different excitation wavelengths

“…25 Structural, thermal and optical properties of ceramics Li 2 -MgGeO 4 un-doped and doped with Er 3+ and Ho 3+ ions were described in our previous work. 26 Direct energy band gaps for Li 2 MgGeO 4 with Er 3+ and Ho 3+ are found to be 5.67 and 5.77 eV and they are comparable to the values reported earlier. 5,6 Further results of the Rietveld renement conrmed that Li 2 -MgGeO 4 crystallize in a monoclinic crystal lattice.…”

“…The SEM images illustrate germanate samples LMG-Pr and LMG-Tm, which consist of micrometer-sized and irregular-shaped grains similar to ceramics Li 2 MgGeO 4 containing Er 3+ or Ho 3+ ions. 26 Previous studies for La 3 Ga 5 SiO 14 :Pr 3+ phosphors well demonstrated that the crystalline grains in micron size and irregular morphology can be successfully observed and these effects are related to the high-temperature sintering process. 27 In our case, rare earth doping caused a reduction of the grain size compared to the un-doped ceramics Li 2 MgGeO 4 crystallized in a regular oval-like shape.…”

“… 2 Moreover, no additional phases associated to impurities exist compared to pure Li 2 MgGeO 4 monoclinic phase. 26 It evidently reveals that rare earth doping has no effect on the crystalline structure of germanate ceramics and Pr 3+ (or Tm 3+ ) ions are well entered into the lattice Li 2 MgGeO 4 . The SEM images illustrate germanate samples LMG-Pr and LMG-Tm, which consist of micrometer-sized and irregular-shaped grains similar to ceramics Li 2 MgGeO 4 containing Er 3+ or Ho 3+ ions.…”

“…Our previous spectroscopic investigations 26 revealed that luminescence spectrum measured for un-doped LMG consists of broad band located in the blue/green region with maximum peak emission near 500 nm depending on the excitation wavelength. Broad emission is associated to the occurrence of magnesium in LMG ceramic host.…”

“… 27 In our case, rare earth doping caused a reduction of the grain size compared to the un-doped ceramics Li 2 MgGeO 4 crystallized in a regular oval-like shape. 26 Moreover, the SEM-BS images for ceramic samples LMG-Pr and LMG-Tm are also presented in Fig. 2 .…”