A NEW STRUCTURAL MODEL FOR LITHIUM-NIOBATE

A new model based on the crystal field theory is proposed for LiNbO3. According to this the central position of the Nb ions in oxygen octahe dra is energetically unstable leading to the splitting of the potentia l energy curve into the one having two equivalent off-centered minima. The phase transition temperature T-c is related to the average height of the barrier existing between these energy minima. The model explai ns satisfactorily some of the properties of LiNbO3 in the paraelectric and ferroelectric phases, which were not fully understood by earlier models.