High-pressure X-ray diffraction study, optical properties, and applications of CaMoO4:Eu3+ nanosheets in white LEDs

Abstract Red-emitting CaMoO4:Eu3+ nanosheets were prepared via a facile precipitation method at room temperature without any organic additives. The structural characterization indicates that these nanosheets are single-crystalline with an average diameter of ∼1.657 μm and a thickness of ∼10 nm. We investigated the high-pressure behaviors of bulk CaMoO4 and CaMoO4:Eu3+ nanosheets by in situ high-pressure synchrotron angle-dispersive X-ray diffraction (XRD) technique at room temperature with the pressures up to 35.0 and 40.1 GPa, respectively. Two pressure-induced phase transitions were observed for both bulk CaMoO4 and CaMoO4:Eu3+ nanosheets in the range of studied pressure. The two high-pressure phases were analyzed and identified to be monoclinic structures with I2/a and P21/n space group, respectively. The compressibility of the CaMoO4 is highly non-isotropic, and the c-axis is more compressible than a-axis and b-axis. Furthermore, the compressibility of the c-axis of CaMoO4:Eu3+ nanosheets is greater than that of bulk CaMoO4. On the release of pressure from 35.0 to 40.1 GPa, the initial phase is recovered, implying that the observed structural modifications are reversible. CaMoO4: Eu3+ sheets also show higher luminescence efficiency that of bulk CaMoO4: Eu3+, which is reflected in higher Ω2 value. The continuous shift of emission peaks indicates the changes in local symmetry of Eu3+ with pressure, which is consistent with our high-pressure XRD study. The potential applications of CaMoO4:Eu3+ nanosheets were explored and our findings show that white light with excellent color quality (CRI>90) and a high LER up to 345 lm/W could be achieved.