The structural changes between NH4VO3 and V2O5 are discussed from the results of decomposition and subsequent curing experiments starting with single crystals of NH4VO3 with well developed bc and ac planes. The structural change from NH4VO3 to V2O5 was divided into five steps, including the first step up to 150 degrees C to keep the original NH4VO3 structure and the final 5th step to be V2O5. The preferred orientation of V2O5 crystallites in particles was found to be strongly influenced by the heating rate. The crystal heated up to the 2nd step (150-180 degrees C) could recover exactly the same single crystal by curing in saturated vapour of NH3-H2O at 25 degrees C. The curing of crystals heated above the 4th step (above 210 degrees C) resulted in a polycrystalline powder of NH4VO3. Structural changes during decomposition and curing between NH4VO3 and V2O5 are discussed.