Effects of aging time on phase, morphology, and luminescence by two-photon processes of BiPO4:Er3+, Yb3+ in the solvothermal synthesis

• The successful co-doping of Er2+ and Yb3+ ions in BiPO4.
• The phase change of BiPO4:Er3+, Yb3+ with the extension of aging time.
• The morphology control of BiPO4:Er3+, Yb3+ by varying aging time.
• The highest UC emission intensity of BiPO4:Er3+, Yb3+ with monoclinic phase.

BiPO4:Er3+, Yb3+ phosphors were synthesized by the solvothermal process. The phase transformation, morphology, and UC luminescent property were characterized by different analytical techniques. The aging time has obvious influence on the phase, morphology, and luminescence of the samples. With the extension of aging time, the phase of BiPO4:Er3+, Yb3+ phosphors changes from hexagon to monocline. The morphology changes from nanorods through nanorugbies to microoctahedra. Under the excitation at 980 nm, BiPO4:Er3+, Yb3+ phosphors show green and red UC emissions, which originate from the (2H11/2, 4S3/2) → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+ ions. The green and red UC emission intensities increase gradually with the increase of pumping power. On the basis of the luminescent properties, one can conclude that the two-photon process is involved in green and red UC emissions.