Enhanced near infrared reflectivity in hierarchical porous La2Zr2O7 microspheres produced by electro-spraying assisted phase inversion method

Abstract

La2Zr2O7 (LZO) has been identified as a promising material for TBCs due to its low thermal conductivity and high phase stability. However, radiative thermal conductivity of LZO significantly increases at high temperature, leading to the deterioration of the thermal insulation performances. In this study, LZO microspheres were fabricated by electro-spraying assisted phase inversion method (ESP). The LZO-ESP microspheres consisted of a surface layer and internal hierarchical structure, showed enhanced near-infrared reflectivity. The reflectivity peak of 95% occurred in the LZO-ESP microspheres sintered at 1400 °C for 2 h, which is higher than those of both commercial hollow and solid microspheres. Both the moderate porosity of ~50% and the ~0.8 μm surface pores contributed to the high reflectivity. Additionally, the phase and hierarchical structure of the LZO-ESP microspheres were fairly stable until 1500 °C, which can meet the requirement for thermal insulation coatings in hyperthermal environments.