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Phase transitions of sodium niobate, prepared by solid state synthesis method, are examined by using dielectric measurements in order to contribute to the clarification of its structural behavior below 400 [degree]C. The results have shown the existence of the Q polymorph at room temperature, which has undergone a transition to the R polymorph upon heating through a temperature region between 265 and 326.5 [degree]C.

X-ray diffraction study followed by extended x-ray absorption fine structure analysis are applied to study the phase transition of the piezoelectric perovskite [K.sub.0.5][Na.sub.0.5]Nb[O.sub.3] the structural changes of the material. The phase transitions of the perovskite are found as an effect of the long-range order while the placement of the atoms in the immediate vicinity remains largely unaffected.