Phase transition study in PLZT ferroelectric ceramics by mechanical and dielectric spectroscopies

Measurements of anelastic and dielectric spectroscopies have been conducted in (Pb/La)(Zr/Ti)O3 (PLZT) ferroelectric ceramics, with Zr/Ti = 65/35 and with La = 5 at.% and 8 at.%. Both the anelastic and the dielectric results have shown the presence of ferroelectric–paraelectric phase transitions around 250 °C for PLZT 5/65/35 and around 150 °C for PLZT 8/65/35, where the shift of the maximum elastic (electric) susceptibility for low temperatures with increase of lanthanum amount can be observed. The behavior of the relative variation of the elastic moduli as a function of the temperature was compared to the Landau-Devonshire theory of phase transitions. These results revealed the change of the kind of coupling between strain and order parameter in the ferroelectric–paraelectric phase transition with the increase of lanthanum concentration.