Boosting the Humidity Performances of Na_0.5Bi_xTiO₃ by Tuning Bi Content

In the field of humidity sensors, a major challenge is how to improve the sensing performance of existing materials. Based on our previous work on Na_0.5Bi_0.5TiO₃, a facile strategy of tuning the Bi content in the material was proposed to improve its sensing performance. Na_0.5Bi_xTiO₃ (x = 0.3, 0.35, 0.4, 0.45) nanocomposites were synthesized by a hydrothermal method. Humidity sensing properties of these nanocomposites were investigated in the relative humidity range of 11% to 95%. Our results show that, compared to the sensor based on nominally pure sample (Na_0.5Bi_0.5TiO₃), the sensor based on Na_0.5Bi_0.35TiO₃ exhibits boosted sensing performance of excellent linear humidity response in the humidity range of 11-75% relative humidity, lower hysteresis value, and faster response/recovery time. The improvement of the sensing performance was argued to be the reason that the proper reduction in Bi content leads to a minimum value of oxygen-vacancy concentrations, thereby weakening the chemical adsorption but enhancing the physical adsorption. These results indicate that the proper underdose of the Bi content in Na_0.5Bi_0.5TiO₃ can greatly boost the sensing performance.