Insight on the morphotropic phase boundaries in (1-x)Pb(Mg_1/3Nb_2/3)-xPbTiO₃ single crystals via birefringence microscopy.

The peculiar phenomena of giant piezoelectric effect observed at the morphotropic phase boundaries (MPB) in polar-oxide single crystal solid solutions (such as (1-x)Pb(Mg_1/3Nb_2/3)-xPbTiO₃ (PMN-PT) and PbZrTiO₃) has gained traction in the past decade in both solid-state physics and device engineering fields. Particularly, for compositions of PMN-PT that are 0.29

To date, researchers have used neutron diffraction, high-resolution X-ray diffraction, dielectric spectroscopy,^[1] and piezo-force microscopy methods^[2] to map the change in symmetry in the MPB. These methods enable one to track observed transitions in symmetry to accurate phase boundaries however, a quantitative understanding of the role of domain orientation in the MPB is yet to be presented.

We use a technique called “birefringence microscopy”, which produces a false color map of the cumulative phase shift and the optical orientation of the extraordinary and ordinary light waves as they pass through the crystal.^[3] Our contribution aims to (a) bring insight into the advantage of birefringence microscopy to map the MPB in ferroelectrics^[4,5] and, (b) present a quantitative understanding of the change in crystal symmetry and optical orientation with temperature in the MPB region for a range of compositions. The current work will cover the aims presented above for a prototypical ferroelectric PMN-PT.

[1] Singh, A. K. et al. Physical Review B 74.2 (2006): 024101.

[2] Deng, C. et al. Advanced Materials 33.43 (2021): 2103013.

[3] Glazer, A. M. et al. Proc. of the Royal Society of London. 452.1955 (1996): 2751-2765.

[4] Gorfman, S., et al. Journal of Applied Crystallography 45.3 (2012): 444-452.

[5] Shuvaeva, V. A., et al. Journal of Physics: Condensed Matter 17.37 (2005): 5709.