This article reports single-step molten salt synthesis to prepare single-crystal, platelike NaNbO3 particles without the Bi2O3 byproduct. In the previous method of two-step molten salt synthesis, platelike Bi2.5Na3.5Nb5O18 particles have been prepared by heating a mixture of Bi2O3,Na2CO3, and Nb2O5 in molten NaCl; the particles are then converted to platelike NaNbO3 particles by reaction with Na2CO3 in molten NaCl. The obtained NaNbO3 particles are polycrystalline, and Bi2O3 particles form as a byproduct. In the present method, single-crystal, platelike NaNbO3 particles without the Bi2O3 byproduct are obtained by heating mixtures of Bi2O3, Na2CO3, and Nb2O5 with molar ratios of 5:7:10 (the composition of Bi2.5Na3.5Nb5O18) and 5:5:8 (the composition of Bi2.5Na2.5Nb4O15) in molten NaCl at 1225 degrees C for 12h. During heating, platelike Aurivillius (Bi2.5Na3.5Nb5O18 and Bi2.5Na2.5Nb4O15) particles are formed first and these then react with NaCl to form platelike NaNbO3 particles, BiCl3, and Na2O. BiCl3 evaporates from the system and Na2O is washed out after heating. Thus, single-phase NaNbO3 is obtained. Sluggish conversion from the Aurivillius phases to NaNbO3 is responsible for the formation of single-crystal particles.