Antiferrodistortive phase transition in pseudorhombohedral (Pb0.94Sr0.06)(Zr0.550

Abstract

The controversies about the structure of the true ground state of pseudorhombohedral compositions of Pb(Zr x Ti 1-x )O 3 (PZT) are addressed using a 6% Sr 2+ substituted sample with x=0.550. Sound velocity measurements reveal a phase transition at T c~2 79K. The temperature dependence of FWHM of (h00) pc peaks and the unit cell volume also show anomalies around 279K even though there is no indication of any change of space group in the synchrotron X-ray powder diffraction (SXRD) patterns. The neutron powder diffraction patterns reveal appearance of superlattice peaks below T c~2 79K confirming the existence of an antiferrodistortive phase transition. The Rietveld analysis of the room temperature and low temperature SXRD data below T c shows that the structure corresponds to single monoclinic phase in the Cm space group while the analysis of neutron powder diffraction data reveals that the structure of the ground state phase below T c corresponds to the Cc space group. Our analysis shows that the structural models for the ground state phase based on R3c space group with or without the coexistence of the room temperature monoclinic phase in the Cm space group can be rejected.2

Epitaxial ferroelectric interfacial devices

“…296,297 At x ≈ 0.52, PZT is characterized by the coexistence of tetragonal, rhombohedral, and a more recently identified intermediate monoclinic phase, [298][299][300][301][302][303] defining the so-called morphotropic phase boundary; such phase coexistence is responsible for the large piezoelectric response of PZT at this composition. 165,297,[304][305][306] In the context of interfacial ferroelectric devices, the tetragonal phase of PZT is the most interesting on account of the higher Curie temperature and a larger ferroelectric polarization along the tetragonal axis. 174,235,301,[307][308][309][310] The epitaxial growth of thin PZT films has been demonstrated on several substrates using various deposi- or on undoped SrTiO 3 with a conducting oxide buffer layer, which provide a good template for the growth of tetragonal PZT (x < 0.5).…”

Detailed dielectric and rietveld analysis of Sr2+ substituted PZT–PMN ceramics

“…Besides, a number of reports have also been published in the recent years on the effect of dopants on the dielectric and electromechanical response of PZT ceramics. Solanki et al [12] have reported that PZT doped with 6 % Sr 2? shows the presence of Cc space group.…”

Confirmation of the monoclinic Cc space group for the ground state phase of Pb(Zr0.525Ti0.475)O3: A combined synchrotron X-ray and neutron powder diffraction study

“…5(c) that the intensity of the (1/2 1/2 1/2) pc peak is too small to be observable above the background counts/fluctuations. In fact, the calculated intensity of this peak is only ~0.12% of the strongest (111) pc perovskite reflection, which is of the order of the background counts in our neutron diffraction data 24 . It is important to emphasize that the non observation of (1/2 1/2 1/2) pc superlattice peak in the neutron diffraction pattern is as enigmatic as the non observation of (3/2 1/2 1/2) pc , (3/2 3/2 1/2) pc and (5/2 1/2 1/2) pc superlattice reflections in the SXRD patterns, as the SXRD intensities of these peaks is comparable to the neutron intensity of the (1/2 1/2 1/2) pc peak.…”

“…However, the non-observation of the weak (1/2 1/2 1/2) pc superlattice peak in the neutron powder diffraction patterns is as enigmatic as the non-observation of the rather intense neutron (3/2 1/2 1/2) pc, (3/2 3/2 1/2) pc and (5/2 1/2 1/2) pc superlattice peaks in the synchrotron X-ray powder diffraction patterns. Most likely, it is because the intensity of these reflections is too small 24 ( 0.1% of the most intense (110) pc peak) to be observable above the background counts for both the neutrons and the X-rays. In view of this, we recently 24, 25 adopted an alternative strategy for resolving the Cc versus R3c controversy for the ground state of PZT.…”

“…The value of χ 2 in all the three refinement is nearly same (~1.75) and also there is no significant difference in the quality of fits using the three two phase models. In view of this, the Cm space group model has to be preferred over the two phase R3m+Cm structural models since the number of refineable parameters is much less (24) than that for the two phase (37) models for a nearly comparable χ 2 value. Thus, we conclude that our sample of PZT525 is nearly single phase monoclinic at 10K and at the SXRD level its space group is Cm.…”