Photoluminescence of complete solid solutions α-Y1-xEuxB5O9 by sol-gel synthesis and thermal decomposition from Y1-xEux[B6O9(OH)3].

Completed solid solutions of Y 1- x Eu x [B 6 O 9 (OH) 3 ] were prepared by boric acid flux method and the structure of Eu[B 6 O 9 (OH) 3 ] was determined by single crystal X-ray diffraction (XRD). The successful cationic doping was supported by the linear change of unit cell parameters obtained by Le Bail fitting on powder XRD. Thermal treatments on Y 1- x Eu x [B 6 O 9 (OH) 3 ] will lead to the dehydration, re-crystallization into TD-α-Y 1- x Eu x B 5 O 9 , and decomposition to α-Y 1- x Eu x B 3 O 6 eventually. For comparison, the sol-gel method was also applied to prepare SG-α-Y 1- x Eu x B 5 O 9. Rietveld refinements on powder XRD was applied to obtain the crystallographic data for α-YB 5 O 9. PL investigation indicated that the existence of hydroxyl groups weakened the Eu3+ charge transfer (CT) in Y 1- x Eu x [B 6 O 9 (OH) 3 ]. In α-Y 1- x Eu x B 5 O 9 , an intense CT absorption was detected and a bright right emission was observed. Moreover, both series of phosphors exhibited a right shift of CT maximum wavelength due to the expansion of unit cell and the delayed concentration at x = 0.6. Complete solid solutions of α-Y 1- x Eu x B 5 O 9 were prepared by either heating the precursors Y 1- x Eu x [B 6 O 9 (OH) 3 ] or direct sol-gel method, and the purity of the borates were verified by careful analyses on powder XRD. Detailed photoluminescence property investigation proved that α-Y 1- x Eu x B 5 O 9 are good red phosphors with a delayed concentration quenching at x = 0.6. Image 1 • Y 1- x Eu x [B 6 O 9 (OH) 3 ] (0 ≤ x ≤ 1) were prepared by boric acid flux method. • Heating Y 1- x Eu x [B 6 O 9 (OH) 3 ] at 670 °C led to the formation of TD-α-Y 1- x Eu x B 5 O 9. • Sol-gel method was also applied to synthesize SG-α-Y 1- x Eu x B 5 O 9. • The CT transition of Eu3+ in Y 1- x Eu x [B 6 O 9 (OH) 3 ] was weakened by hydroxyl groups. • α-Y 1- x Eu x B 5 O 9 have a bright red emission and a concentration quenching at x = 0.6. [ABSTRACT FROM AUTHOR]