Pure tetragonal ZrO2 nanocrystals were prepared at low temperature (85 degrees C). Their proton conductivity measured at 80 degrees C in N-2 is 5.63 x 10(-5) S/cm which is one order of magnitude higher than that of 1.72 x 10(-6) S/cm for the sulfated counterpart or of 4.17 x 10(-6) S/cm reported in the literature for 3-nm crystals of ZrO2-nH(2)O.