Environment-friendly Ca <sup>2+</sup>/Cr <sup>3+</sup> co-doping LaAlO <sub>3</sub> ceramics with excellent infrared radiation performance for energy-saving
Xinglai Yuan, Qinghu Wang, Runke Wu, Shaobai Sang, Yibiao Xu, Liang Xiong, Liping Pan, Bingbing Fan, Yawei Li, Rui Zhang, Jiangtao Li, Olena Volkova
Abstract
Ca<sup>2+</sup>/Cr<sup>3+</sup> co-doped LaAlO<sub>3</sub> infrared radiation (IR) ceramics have been proved as potential energy-saving materials for high-temperature industry due to their high emissivity and high-temperature stability. However, Cr<sup>6+ </sup>formation commonly occurs in material to poses environmental and health risks, such as Cr<sup>6+</sup> dissolution in water and CrO<sub>3</sub>(g) gaseous volatilization. Herein, we combined high emissivity with in-situ detoxification by introducing residual Al<sub>2</sub>O<sub>3</sub> into Ca<sup>2+</sup>/Cr<sup>3+</sup> co-doped LaAlO<sub>3</sub> ceramics. Compared with the undoped ceramics, the addition of 20 wt% residual Al<sub>2</sub>O<sub>3</sub> resulted in a 78.5% reduction to 18.44mg/kg (lower than E.U. standard of 20 mg/kg) in Cr<sup>6+</sup> dissolution and a decrease in 77.8% CrO<sub>3</sub>(g) volatilization. This significant detoxification effect can be attributed to the formation of CaAl<sub>12-x</sub>Cr<sub>x</sub>O<sub>19</sub>. Additionally, as the residual Al<sub>2</sub>O<sub>3</sub> content increased from 5 wt% to 20 wt%, the ceramics maintained high emissivity, above 0.896 in the near-infrared and 0.781 in the mid-infrared band. Furthermore, the IR coating effectively enhanced surface temperature (from 767.1 °C/min to 790.7 °C/min) and heat radiation of heating source, improving the heating rate from 31.7 °C/min to 34.6 °C/min during water heating. This work offers a promising approach for designing environmentally friendly IR ceramics with excellent IR performance for energy-saving applications in high-temperature industry.