The Space Group Symmetry of PSN, PST and PSNT Ferroelectric Relaxors in the Superparaelectric Phase

Abstract

Diffuse X-ray scattering studies were performed for as grown Pb(Sc_1/2Nb_1/2)O₃-PSN, Pb(Sc_0.5Ta_0.5)-PST and Pb(Sc_0.5Nb_0.2Ta_0.3)O₃-PSNT single crystals at 400 K by means of a four-circle single crystal diffractometer equipped with CCD area detector. The superstructure observed yields a cubic unit cell with lattice parameter equals to 0.8181 nm, 0.8150 nm and 0.8140 nm for PSN, PST and PSNT crystals, respectively. The analysis of the extinction rules of diffuse reflections, observed for all the crystals in the superparaelectric phase, leads to a space group Pn¯m instead of the Fm3m space group ascribed previously.

Keywords:

• Ferroelectric relaxors
• Pb(Sc_1/2Nb_1/2)O₃
• Pb(Sc_1/2Ta_1/2)O₃
• Pb(Sc_0.5Nb_0.2 Ta_0.3) O₃
• superstructure
• diffuse X-ray scattering