In this work, the possibility of synthesizing stable tetragonal zirconia nanopowders via polyacrylamide gel method was investigated. In addition, the effects of the sulfation process on the stabilization of metastable tetragonal structure and tetragonal to monoclinic phase transformation were studied. Zirconium oxychloride and zirconium oxynitrate salts were used as the initial salt precursor and the calcination procedure was performed at different temperatures (650-850 degrees C) for 2 h with heating and cooling rates of 5 and 2 degrees C/min. The results showed that in the synthesized powders from zirconium oxynitrate, metastable tetragonal phase was stable up to 850 degrees C. Moreover, heating rate of 5 degrees C/min was concluded as the optimum rate to stabilize the metastable tetragonal phase up to higher temperatures. The addition of sulfate ions into the structure of sulfated zirconia powders synthesized by zirconium oxychloride retarded the tetragonal to monoclinic phase transformation, while in the case of zirconium oxynitrate, this phase transformation was accelerated.