Upconversion thermal enhancement of H-2(11/2)-> I-4(15/2) of Er3+ and blue emission of impurity Tm3+ in Sr-3(PO4)(2):Er3+/Yb3+

A series of Sr2.99-x(PO4)(2):.01Er(3+)/xYb(3+) (x = .02, .04, .06, .08, .10) phosphors in the presence of impurity Tm3+ were synthesized by high temperature solid-state method, and X-ray diffraction results show that these samples are pure R-3 m(166) space group phase. The upconversion luminescence (UCL) of Er3+ and impurity Tm3+ under 980-nm laser excitation were investigated, and the results show that the intense blue UCL of impurity Tm3+ and thermal enhancement of H-2(11/2)-> I-4(15/2) of Er3+ simultaneously exist. When Er3+ doping concentration is kept at .01, both the blue UCL intensity of impurity Tm3+ and green and red UCL intensity of Er3+ reach the maximum at Yb3+ doping concentration of .08. The thermal enhancement effect of H-2(11/2)-> I-4(15/2) of Er3+ was observed as high as 3.27 times from 303 to 723 K, which is because of lattice distortion and phonon-assisted transition. In addition, the optical temperature performance of Sr-2.91(PO4)(2):.01Er(3+)/.08Yb(3+) sample was studied, and the maximum absolute temperature sensitivity was calculated as .00623 K-1 at 538 K. This study suggests that Sr-3(PO4)(2):Er3+/Yb3+ phosphors in the presence of impurity Tm3+ have a promising application prospect as optical temperature sensor at high temperature.