Abstract
Some correlations between the interatomic bond A–X and B–X characteristics, on the one hand, and phase transition nature and temperature, on the other hand, are observed for complex oxides and fluorides with the perovskite structure and the compositions ABX 3 (X─O, F). They have different nature structural phase transitions from the high-symmetry (cubic) phase into the lower-symmetry phase. Their interatomic bond strain values calculating with the use of the earlier submitted elastic model of perovskite-type structure allow rather clear separating one from the other ferroelectric and antiferroelectric and also different rotational nonferroelectric compounds, respectively.