Characterization and sintering of MoO3 prepared by thermal decomposition of hexaammonium heptamolybdate tetrahydrate

MoO3 powders with plate particles have been prepared by heating hexaammonium heptamolybdate tetrahydrate ((NH4)6Mo7O24 · 4H2O) for 1 h at 650 °C. Densification has been performed by hot pressing for 2 h at 630 °C and 30 MPa. Grain-oriented MoO3 ceramics (>98% of theoretical) are fabricated, in which the <010> axis is parallel to the hot pressing direction. Their electrical conductivities have been measured in the temperature range of 100 ° to 600 °C. Sintered MoO3 is a ceramic semiconductor. Activation energies are determined to be 0.49 and 0.76 eV for initial and final stages, respectively.