Fig. 4: Paraelectric-ferroelectric phase boundary and phase diagram.

a Temperature–strain phase diagram of the paraelectric-ferroelectric phase. The dash-line is the fitted phase boundary to the power law. In the ferroelectric side of the phase diagram, the strength of the order parameter is color-coded. The grey data points are reproduced from ref. 10. b Temperature dependence of the order parameter critical exponent β. The error bars represent the standard deviation from the fit.