Ce 3+ -Doped Li 2 Ca 5 Gd(BO 3 ) 5 Phosphors with Multiple Luminescent Centers and High Pressure Sensitivity under Near UV Excitation.

The performance of Ce 3+ -based phosphors under mechanical high pressures becomes attractive due to the potential application as a visual pressure sensor. Li 2 Ca 5 Gd(BO 3 ) 5 was selected as the host for the Ce 3+ doping. Rietveld refinements reveal that rare earth cations occupy M 1, M 2, and M 3 sites, and indeed, the photoluminescent spectra of Li 2 Ca 5 Gd 1- x Ce x (BO 3 ) 5 (0.005 ≤ x ≤ 0.15) exhibit the characteristic of multiple activators, defined as CeI, CeII, and CeIII, with the maximal emission wavelength at ∼444, 419, and 378 nm, respectively. The optimal internal and external quantum efficiencies are 86.29% for x = 0.005 and 20.26% for x = 0.10, respectively, under the NUV excitation at 363 nm. In-situ high pressure emission spectra under 375 nm excitation exhibit an overall red-shift, and the linear pressure susceptibilities up to 6.7 GPa for CeI and CeII centers are -390 and -279 cm -1 /GPa, respectively, which is probably the largest among Ce 3+ -doped oxides and oxysalts. Due to the above superiorities, Ce 3+ -doped LCGB possesses a high potential as a visual pressure sensor, and this is a successful study on the structure-property relationship of inorganic materials.