“Square” hysteresis loops in phase-switching Nb-doped lead zirconate stannate titanate thin films

Abstract

Niobium-doped lead zirconate stannate titanate thin films have been prepared by a modified sol-gel spin on technique, utilizing the hydrolysis-resistant precursor lead acetylacetonate. Films of compositions in the antiferroelectric tetragonal and antiferroelectric orthorhombic phases were prepared and phase-switched with the application of appropriate electric fields. A distinctly “square” hysteresis response was observed in a low titanium, low tin, orthorhombic composition, with a maximum polarization, Pmax, of 40 μC/cm2 and switching field values of Ef = 175 kV/cm and Ea = 75 kV/cm, while varying degrees of squareness, along with lower polarizations and switching fields, were observed in the higher tin, tetragonal compositions. Electric field-induced strains of up to 0.33% have been measured in the orthorhombic composition, with tunable electromechanical coefficients. Film properties showed only slight variation with electrode size over a range of diameters from 0.8 mm to 6.35 mm; large area electrodes are vital for practical actuator and sensor devices. With a capacitance density of 30–35 μF/cm2, films of the orthorhombic composition are promising as power plane decoupling capacitors in multichip modules.