Effect of Yb3+ concentration on upconversion luminescence and optical thermometry sensitivity of La2MoO6: Yb3+, Er3+ phosphors

La2MoO6: Yb3+, Er3+ 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 Er3+ ions. As Yb3+ concentration rises, the green emission intensity increases and reaches the maximum at 2.0% Yb3+ 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)H(11/2 )and S-4(3/2) of Er3+ in temperature range of 293 similar to 533 K. It is interesting to find that Yb3+ concentration has influence on the absolute sensitivity SA, while the relative sensitivity SR is almost independent of Yb3+ content. Furthermore, excellent thermal stability and high temperature sensitivity is also demonstrated in the 2.0% Yb3+-doped sample with the obtained maximum SA and SR as high as 0.008 K-1 and 1.093% K-1, respectively. The experimental results indicate that Yb3+/Er3+ co-doped La2MoO6 phosphors can be excellent candidates for temperature sensing applications. (C) 2021 Optical Society of America