[Upconversion luminescence of Er3+-doped yttrium-stabilized zirconia powders]

Er(3+)-doped yttrium-stabilized zirconia upconversion powders Zr(0.92-x)Y0.08O(1.96-0.5x):xEr(3+) (x = 0.001~0.11) were synthesized via chemical coprecipitation method at 1200 °C for 3 hours. Phase structure and upconversion luminescence spectra of the samples were characterized by X-ray diffractometer and fluorescence spectrometer, respectively. The proposed upconversion mechanism of the samples was discussed. The results indicate that good crystallinity cubic ZrO2 solid solution can be stabilized by introducing 8 mol% yttrium ions. Size and valent differences between trivalent Y(3+) and quadrivalent Zr(4+) ions generate asymmetry and oxygen vacancies, which contribute to the stability of upconversion luminescence properties and luminescence intensity increase of the samples, and expand its practical application fields. Under 980 nm excitation, the samples emit green light centered at 539 nm ((2)H11/2-->(4)I15/2), 552 nm ((4)S3/2-->(4)I15/2) and red light at 656 and 680 nm ((4)F9/2-->(4)I15/2). When Er(3+) doping concentration (0.1 mol%) is low, the main green emission of samples is ascribed to the excited state absorption (ESA) processes; With the Er(3+) concentration increases from 0.1% to 11 mol%, there exist three cross relaxation (CR) processes: (2)H11/2+(4)I15/2-->(4)I9/2+(4)Ii3/2, (4)F7/2+(4)I11/2-->2 (4)F9/2 and (4)I15/2+(4)I9/2-->2 (4)I13/2, causing that the red emissions increase markedly whereas the green emissions decrease. When Er(3+) doping concentration (9 mol%) is high, the sample mainly presents red luminescence due to the dominated CR processes in upconversion process.