Dielectric properties of tetragonal lanthanum modified lead zirconate titanate ceramics

Abstract

Tetragonal La-modified lead zirconate titanate ceramics with a Zr/Ti ratio of 40/60 (x/40/60) with La contents (x) between 0 and 21 at. % were prepared by the mixed oxide method and were subsequently characterized using dielectric spectroscopy. Small La contents tended to diffuse the dielectric response in the temperature region around the phase transition, however, no distinct changes were observed in the paraelectric region. Compositions with intermediate La contents showed a thermally driven (spontaneous) transformation from a relaxor to a normal ferroelectric, i.e., micro-macro domain switching. Materials with a high La content exhibited typical relaxor ferroelectric behavior. The relative thermodynamic stability of the ensemble of micropolar regions is then discussed in reference to that of the long-range ferroelectric state.

Dielectric response of PLZT ceramics x/57/43 across ferroelectric–paraelectric phase transition

“…Weakening the dipole-dipole interactions results in the formation of smaller sized domains. Dai et al (1993) have also shown that at higher La content, the translational symmetry of polarization is disturbed and the local dipole moments with weak coupling between two BO 6 octahedra via A-site cation are established. These weakly cooperating dipole moments produce the diffuse phase transition in the present systems in agreement with the observations of Dai et al (1993Dai et al ( , 1994 for tetragonal PLZT systems.…”

“…Shemin et al (1988) reported the domain-like transition in PLZT under d.c. bias. Dai et al (1993) observed that small La content can diffuse the dielectric response in the temperature region around phase transition in tetragonal PLZTs. The relaxor to normal ferroelectric transition has been attributed to a local to global symmetry transition by them.…”

Spontaneous long and short-range ferroelectric ordering in Pb0.55La0.30TiO3 ceramics

“…15 Possible spontaneous transition ͑not induced by electric field͒ from the relaxor-to-normal ferroelectric phase has been studied mainly by dielectric measurements. 16,17 We did not find in the literature works in which the spontaneous and the electric field-induced relaxor-to-normal ferroelectric transition were investigated by using both short-and long-range order types of structural characterization, namely x-ray absorption spectroscopy ͑XAS͒ and XRD.…”

“…Rather, some works have suggested that the coupling of the ferroelectric phase to the strain is stronger for the tetragonal symmetry than for the rhombohedral one and favors the stabilization of the ferroelectric phase. 17,25,38 C. Structural properties: Short-range order structure Figure 4 shows the Ti K-edge XANES spectra of PLT30 sample as function of temperature. It is well known that the physical origin of the pre-edge feature, labeled A on Fig.…”

“…It is inferred that the large tetragonal strain may play a key part in the spontaneity of this crossover. 17,20 Nevertheless, these investigations were limited to dielectric measurements or to conventional x-ray diffraction ͑XRD͒ techniques at room and higher temperatures. Thus, little information about local structural properties or possible transitions at low temperatures is available.…”