Relaxor Behavior of the 0.9BaTiO₃–0.1La(Mg_1/2Ti_1/2)O₃ Solid Solution

Abstract

Low‐frequency dielectric response of air‐ and oxygen‐sintered ceramics with the composition 0.9BaTiO3–0.1La(Mg1/2Ti1/2) O3 (0.9BT–0.1LMT) has been studied in the temperature range of 12–550 K. In comparison with pure BT, in 0.9BT–0.1LMT the dielectric permittivity maximum is shifted by almost 300 K toward lower temperatures. Both real and imaginary parts of dielectric permittivity of the solid solution, in the range 12–150 K, show a strong frequency‐dependent behavior, which is typical of relaxors. On the basis of the model of exponential cluster size distribution and the Cole–Cole equation, the degree of interaction between the polar clusters was estimated. It was shown that the oxygen vacancies arising during sintering at high temperatures did not affect noticeably the relaxor properties of the material. The role of heterovalent La3+/Ba2+ and Mg2+/Ti4+ substitutions in the relaxor behavior formation is discussed.

Lead‐Free Relaxor Ferroelectrics

“…For heterovalent substitution on the A-site relaxor behavior is induced at moderate doping levels (e.g., x = 0.10 for Ba 1Àx Bi 2x/3  x/3 TiO 3 70 The latter systems are of particular interest. 62,63]. Second, appearance of the relaxor behavior in systems without nominal charge disorder is unique and has not been well understood so far.…”

Ferroelectric-to-relaxor transition behaviour of BaTiO3ceramics doped with La(Mg1/2Ti1/2)O3

“…It is characterized by a monoclinic perovskite structure (Z = 4, space group P2 1 /n) due to oxygen octahedra tilting and B-site cation (Mg/Ti) ordering [8]. It has been shown that small additions of LMT modify strongly the dielectric response of BT, decreasing the transition temperature to a paraelectric phase about 30 K/1 mol% of LMT [11]. Ceramics of the BT-LMT system were found to exhibit mainly relaxor features at doping levels as low as 5 mol% of LMT.…”

Ultrasonic and piezoelectric properties of the BT–LMT ceramic system

“…It was shown that BT ceramics doped with 2.5 mol.% of LMT exhibit the typical features of both the ferroelectric and the relaxor, 3 while BT-10% LMT demonstrates solely the relaxor properties. 4 Dielectric investigations of BT-LMT performed by the macroscopic methods (averaging over many grains) and on the nanoscale level (in a single grain) have proved the presence of polar nanoregions in the ceramics at temperatures above the dielectric permittivity peak. 4,5 Recently, homogeneous ceramics (1 − x)BaTiO 3 -xLa(Mg 1/2 Ti 1/1 )O 3 ((1 − x)BT-xLMT) with the compositions x = 0.025, 0.05, 0.075 and 0.1 were obtained.…”

“…4 Dielectric investigations of BT-LMT performed by the macroscopic methods (averaging over many grains) and on the nanoscale level (in a single grain) have proved the presence of polar nanoregions in the ceramics at temperatures above the dielectric permittivity peak. 4,5 Recently, homogeneous ceramics (1 − x)BaTiO 3 -xLa(Mg 1/2 Ti 1/1 )O 3 ((1 − x)BT-xLMT) with the compositions x = 0.025, 0.05, 0.075 and 0.1 were obtained. The X-ray diffraction studies 6 have revealed the tetragonal (P4mm) perovskite structure for the compositions with x < 0.025 and the cubic (Pm3m) for x > 0.05 at the room temperature.…”