To advance the synthesis of nano-crystallite gahnite, this article reports the effect of solution pH on the gel combustion performance and the final gahnite particle characteristics. The gels were prepared at different pHs, 2.5-10.5, and the obtained precursors were calcined at four temperatures, ranging 600-1200 degrees C. DTA-TG, XRD, BET and TEM were employed to characterize the combustion process and nano-scale structural changes due to thermal treatment. The experiments indicate while the pH has little effect on the crystal size of gahnite, agglomeration of crystallites can be controlled by pH. The alkali environments provides the better condition to achieve maximum specific surface area and the thermal treatment at 800 degrees C causes transformation of amorphous phase into crystallite phase. In conclusion, the pure gahnite with particle size below 20 nm was synthesized successfully at pH of 7, which is flexible from engineering point of view. (C) 2015 Published by Elsevier BM.