Mechanical response and thermal expansion characteristics of spark plasma sintered Zr–La–B–C(O)-based precursor-derived ceramics

In this work, a Zr–La–B–C(O)-based precursor-derived ceramic system is spark plasma sintered at 1600°C for 10 min. Chemical and phase analysis of the sintered ceramic reveals nanocrystalline ultra-high temperature (UHT) phases of ZrB2, ZrC, and La2Zr2O7 embedded in a glassy carbon matrix. A comprehensive evaluation of mechanical properties and thermal expansion characteristics correlates well with the presence of phases. Depth-sensing nanoindentation exemplifies high elastic recovery of 91% typically seen in glassy carbons. The hardness and Young’s modulus measured to be ∼4.5 and ∼29.5 GPa respectively, seem to be governed mainly by the presence of glassy carbon, and secondarily by stiff B–C bonds and the UHT phases. The linear coefficient of thermal expansion measured from 130°C to 1550°C is ∼7.9 × 10−6 K−1 and the thermal expansion behaviour is found to be strongly driven by the constituent UHT phases.