Thermal stress accommodation in dip cast lead zirconate-titanate ferroelectric films on flexible substrates

Piezoelectric thin films were dip coat deposited onto flexible metal substrates to investigate the dependence of dielectric and ferroelectric properties on the coefficient of thermal expansion mismatch and substrate thickness. The bending stiffness was controlled by the thickness of the substrate. Grazing incidence X-ray diffraction displayed distinct peak splitting for [Pb_0.98▪_0.01(Zr_0.52Ti_0.48)Nb_0.02O₃] on flexible Pt, Ni, Ag, and stiff Ni substrates, where the out-of-plane d-spacing and integrated peak area for c-domains were highest with the largest film compressive stress. As expected, lead zirconate titanate (PZT) films on stiff Si were under tensile stress and contained more in-plane domains. The dielectric permittivity was highest in PZT on stiff Si and lowest for PZT on thick Ni, while remanent polarization displayed the opposite trend, commensurate with the residual stress state as well as the resistance to bending in thick substrates as a strain-relief mechanism. The irreversible Rayleigh coefficient decreased dramatically upon poling for PZT on flexible substrates compared to PZT on stiff substrates; the (Formula presented.) ratio was 56% higher in PZT on a flexible Ni substrate relative to a stiff Ni substrate at 100 Hz prior to electrical poling. This investigation distinguishes the impact of substrate flexibility from thermal expansion on ferroelectric domain mobility and provides dip-coating conditions for high-quality piezoelectric films on any substrate.