Order‐Disorder Phenomenon in Lead Scandium Tantalate

Abstract

Lead scandium tantalate (PST) is a ferroelectric relaxor with the perovskite structure of A(B'B)03. By suitable heat treatment, the B-site cations can be brought from a structurally disordered state into various degree of ordering. The degree of ordering is strongly affected by the amount of vacancies present in the materials. To suppress PhO loss during the sintering or annealing process, a PbO-rich atmosphere is supplied by materials having high PhO vapor pressure, such as PbZr03. For PST ceramics with nearly zero weight loss, very long annealing times and higher annealing temperatures are required for ordering. The higher PbO-loss materials are found to be easily ordered. The introduction of a reducing atmosphere during annealing enhances the ordering process. The ordering process is characterized quantitatively by X-ray diffraction and qualitatively by Raman spectroscopy. [

Structural, Dielectric, and Pyroelectric Properties of (1−x)PbSc0.5Ta0.5O3–(x)PbHfO3 Ceramics

“…At low x ( x =0.00 and 0.05), the grain size is 1–3 μm, when x is greater than 0.05 ( x =0.10, 0.15, and 0.20), the grain size increases, with a scale of 4–6 μm. The sintering temperatures of PST and PbHfO 3 ceramics are 1560° and 1200°C, respectively 1,18 . While the PSTH( x ) ceramics are sintered by hot‐pressing at the same conditions (25 MPa, 1320°C, 2 h), then the low‐temperature sintering composition PbHfO 3 makes the grain size grow.…”

“…L ead scandium tantalate (PbSc 0.5 Ta 0.5 O 3 , or PST) is a complex perovskite type of A(B′B″)O 3 , where B′ is a low‐valence cation and B″ is a high‐valence cation. The differences in the ionic radii and charge between the two B ions are sufficient to allow for an ordered structure 1–3 . Cross and colleagues demonstrated that the degree of B‐site order had a strong effect on the nature of the dielectric response, the peak permittivity, and phase transition temperature 4 .…”

The Effect of Excess PbO on Dielectric and Pyroelectric Properties of Lead Scandium Tantalate Ceramics

“…L ead scandium tantalate (PbSc 0.5 Ta 0.5 O 3 , or PST) have attracted great research interest due to its order–disorder phenomenon in the past decades 1 . PST is a ferroelectric with the perovskite structure of A(B′B″)O 3 2 .…”

New Relaxors with the Perovskite Structure

“…At the same time, disordered compounds and solid solutions are known to undergo order-disorder phase transition [27][28][29][30] and, certainly, such transitions should exist in the relaxors. This problem has been studied soon after the discovery of the relaxors [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]. It was shown that long high-temperature annealing of the simplest relaxors PSN and PST leads to the ordering with the cell doubling [32][33][34][35][36][37][38][39][40][41].…”