Effect of annealing temperature on the microstructure, dielectric, and microwave absorption performance of precursor blends derived ZrSiOCN ceramics

The ZrOC ceramic derived from polyzirconoxane (PZC) precursor, usually composed of ZrO₂ and ZrC, is a high temperature ceramic material possessing great potentialities to be applied in harsh environments. However, the relatively high electrical conductivity of ZrC usually results in the limited electromagnetic wave absorption performance, and it's an effective way to adjust the relative complex permittivity of ZrOC ceramics by introducing SiCN ceramics with low dielectric properties. In this work, polyzirconoxane (PZC) and polysilazane (PSN) precursors were blended at the weight ratio of 1:1 firstly, then the blends were cured and pyrolyzed to prepare the ceramics composed of Zr compounds and Si-containing amorphous ceramics. As the annealing temperature rises, t-ZrO₂, turbostratic carbon, and ZrC_0.347N_0.653 grains appear, and the real and imaginary parts of the permittivity gradually increase. It can be found that ZrC_0.347N_0.653 and free carbon form a typical core-shell structure when the annealing temperature is 1500 °C, and the as-obtained ceramic possesses remarkable microwave absorption ability. The minimum reflection loss is −22.7 dB at 12.02 GHz, and the value of effective absorption bandwidth is 1.65 GHz with a sample thickness of 2.0 mm.