Ferroelectric to relaxor crossover and dielectric phase diagram in the BaTiO3–BaSnO3 system

Abstract

The (1−x)BaTiO3–xBaSnO3 (0⩽x⩽0.30) perovskite solid solution ceramics were prepared by solid state reaction and studied by dielectric spectroscopy. The complex dielectric permittivity was measured as a function of frequency (0.1Hz–100kHz) in the temperature (T) range of 123–573K. The transition from the high-temperature paraelectric state where the dielectric constant obeys the Curie-Weiss law to the ergodic cluster state is found to occur at the same temperature of 485K in all the compositions of x⩾0.04 and at lower temperatures in those with a smaller x. For 0⩽x⩽xc=0.19, the temperature of the dielectric peak Tm, corresponding to the diffuse transition from the ergodic polar cluster state to the ferroelectric state, decreases with increasing x and does not depend on frequency. The diffuseness of the peak gradually increases. For x>xc, the permittivity exhibits relaxor behavior with the frequency-dependent Tm satisfying the Vogel-Fulcher law. The temperature variation of the permittivity on the high-temperature slope of the peak (T>Tm) is characterized by the characteristic Lorenz-type quadratic law for relaxors, with the diffuseness increasing with the increase of x. The mechanisms of the dielectric response in different parts of the phase diagram are discussed. In particular, the crossover from diffuse ferroelectric phase transition to relaxor ferroelectric behavior is attributed to the appearance at x>xc of the additional dielectric contribution arising from the flipping of the local polarization of the polar clusters. The temperature-composition phase diagram of the Ba(Ti1−xSnx)O3 system has been established, which delimits the paraelectric, ergodic polar cluster, nonergodic ferroelectric, and relaxor phases (states) and indicates the crossover from ferroelectric to relaxor behavior at x=xc.

Ferroelectric Relaxor Behavior and Spectroscopic Properties of Ba<SUP>2+</SUP> and Zr<SUP>4+</SUP> Modified Sodium Bismuth Titanate

“…[7] In recent years, therefore, some countries have required all new electronic products to be lead-free for the environmental protection and human health. [8] Hence, many studies are focused on the BaTiO 3 -based materials such as BaTiO 3 -BaZrO 3 , [9] BaTiO 3 -BaSnO 3 , [10] BaTiO 3 -BiAlO 3 , [11] and BaTiO 3 -CaTiO 3 -SrTiO 3 [12] because these BaTiO 3 -based lead-free relaxor ferroelectrics show relatively high dielectric and…”

Influence of thermal conditions on the electrocaloric effect in a multilayer capacitor based on doped BaTiO3

“…At about 373 K, the PðEÞ dependence is close to linear, which is typical for paraelectrics or linear dielectrics. The presence of polarization above room temperature may be due to the polar nanoregions found in the BaTi 1Àx Sn x O 3 solid solutions 27 with x > 0.12 which are also the cause of a significant frequency dispersion of permittivity observed by us (Fig. 5).…”

“…Thereby, in BaTi 1Àx Sn x O 3 at x > 0.12, only direct rhombohedral -cubic transition, which is often named as pinched phase transition in literature. 27,31,32 Investigations of the thermal and dielectric properties (thermal expansion, heat capacity, and permittivity) confirmed the existing of one phase transition near room temperature.…”

“…Such a behavior of permittivity of BaTi 0:86 Sn 0:14 O 3 is characteristic of relaxor properties which were found for the solid solutions BaTi 1Àx Sn x O 3 at x > 0:12. 27 Information on spontaneous polarization P at various temperatures was obtained from measurements of the hysteresis loops (Fig. 6).…”

“…The saturated value of P equals to $18 C/cm 2 is close to polarization observed for barium titanate ($20-25 C/cm 2 ). 28 The investigations of BaTi 1Àx Sn x O 3 solid solutions 27,29,30 have shown that increase in Sn concentration is accompanied by a shift of decrease of the phase transition temperature between cubic and tetragonal phase, whereas the other two transitions are shifted to higher temperatures. Thereby, in BaTi 1Àx Sn x O 3 at x > 0.12, only direct rhombohedral -cubic transition, which is often named as pinched phase transition in literature.…”