Lei Liu,Fangyi Yin,Guiyuan Zhao,Limei Zheng,Xiuwei Fu,Zhitai Jia,Xutang Tao
B 0 . 7 7 Ca 0 . 2 3 TiO 3 (BCT) single crystal has been widely studied as a promising lead-free ferroelectric material. In this work, high-quality BCT crystal was successfully grown by the Czochralski (CZ) method. The as-grown crystal is crack-free and shows black coloration. It possesses a high dielectric stability over a wide temperature range, while the dielectric loss is rather small below 90 ∘ C. Furthermore, it possesses excellent ferroelectric properties with residual polarization strength ( P r ) and coercive field ( E c ) of 17.93 μ C/cm 2 and 8.47 kV/cm, respectively. Besides, BCT crystal shows large electromechanical coupling factors, with k t , k 3 1 , k 3 3 and k 1 5 of 0.535, 0.254, 0.714 and 0.721, respectively. The piezoelectric coefficients d 3 1 , d 3 3 and d 1 5 are measured to be − 36.5, 130 and 246 pC/N, respectively.
Optical thermometry based on the upconversion (UC) luminescence intensity ratio (LIR) has attracted considerable attention because of its feasibility for achievement of accurate non-contact temperature measurement. Compared with traditional UC phosphors, optical thermometry based on UC single crystals can achieve faster response and higher sensitivity due to the stability and high thermal conductivity of the single crystals. In this study, a high-quality 5 at% Yb 3+ and 1 at% Ho 3+ co-doped Gd 0.74 Y 0.2 TaO 4 single crystal was grown by the Czochralski (Cz) method, and the structure of the as-grown crystal was characterized. Importantly, the UC luminescent properties and optical thermometry behaviors of this crystal were revealed. Under 980 nm wavelength excitation, green and red UC luminescence lines at 550 and 650 nm and corresponding to the 5 F 4 / 5 S 2 → 5 I 8 and 5 F 5 → 5 I 8 transitions of Ho 3+ , respectively, were observed. The green and red UC emissions involved a two-photon mechanism, as evidenced by the analysis of power-dependent UC emission spectra. The temperature-dependent UC emission spectra were measured in the temperature range of 330–660 K to assess the optical temperature sensing behavior. At 660 K, the maximum relative sensing sensitivity ( S r ) was determined to be 0.0037 K −1 . These results highlight the significant potential of Yb,Ho:GYTO single crystal for optical temperature sensors. Graphical abstract
危险品化学品经营许可证（带存储）