3. Results and discussion
Fig. 1 shows the XRD pattern of the samples. In Fig. 1c, all nine peaks can be indexed as hexagonal ZrB2. The lattice constants are a=3.162 and c=3.518 Å, in good agreement with a=3.170 and c=3.530 Å (JCPDS card# 75-1050). No evidence of crystalline Zr, ZrO2, NaCl or other impurities are observed. As the reaction temperature was decreased from 700 to 500 °C ( Fig. 1a–c), the diffraction peaks broadened indicating the crystalline particles of the products were becoming smaller.