 The thermal decomposition of [NH4]2[MoS4] leads to molybdenum trisulfide (MoS3), ammonia (NH3) and hydrogen sulfide (H2S), beginning at 155 °C till 280 °C.MoS3 then decomposes again to molybdenum disulfide (MoS2) in a broad temperature range from 300 °C to 820 °C.Perfect decomposition to MoS2 under inert gas requires at least 800 °C according to the following reaction,

but it can also be achieved at 450 °C, if there is enough hydrogen.