Abstract

${\rm{L}}{{\rm{a}}_2}{\rm{Mo}}{{\rm{O}}_6}:\;{\rm{Y}}{{\rm{b}}^{3 +}},\;{\rm{E}}{{\rm{r}}^{3 +}}$ upconversion (UC) micro-crystals with a tetragonal structure were fabricated through a modified sol–gel method. The samples are found to be spherical in shape with a diameter of about 300 nm. Upon excitation of 980 nm light, the UC emission spectra of the phosphors exhibit green and red bands corresponding to the characteristic transitions of ${\rm{E}}{{\rm{r}}^{3 +}}$ ions. As ${\rm{Y}}{{\rm{b}}^{3 +}}$ concentration rises, the green emission intensity increases and reaches the maximum at 2.0% ${\rm{Y}}{{\rm{b}}^{3 +}}$ content, while the ratio of green/red emission intensities (${I_G}/{I_R}$) declines monotonically. Temperature sensing capability was studied employing the fluorescent intensity ratio technique from the thermally coupled levels ${^2{{\rm{H}}_{11/2}}}$ and ${^4{{\rm{S}}_{3/2}}}$ of ${\rm{E}}{{\rm{r}}^{3 +}}$ in temperature range of 293${\sim}$533 K. It is interesting to find that ${\rm{Y}}{{\rm{b}}^{3 +}}$ concentration has influence on the absolute sensitivity ${S_A}$, while the relative sensitivity ${S_R}$ is almost independent of ${\rm{Y}}{{\rm{b}}^{3 +}}$ content. Furthermore, excellent thermal stability and high temperature sensitivity is also demonstrated in the 2.0% ${\rm{Y}}{{\rm{b}}^{3 +}}$-doped sample with the obtained maximum ${S_A}$ and ${S_R}$ as high as ${0.008}\;{{\rm{K}}^{- 1}}$ and ${1.093}\% \;{{\rm{K}}^{- 1}}$, respectively. The experimental results indicate that ${\rm{Y}}{{\rm{b}}^{3 +}}/{\rm{E}}{{\rm{r}}^{3 +}}$ co-doped ${\rm{L}}{{\rm{a}}_2}{\rm{Mo}}{{\rm{O}}_6}$ phosphors can be excellent candidates for temperature sensing applications.

© 2021 Optical Society of America

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