Microstructural development in sol-gel derived lead zirconate titanate thin films: The role of precursor stoichiometry and processing environment

Abstract

The role of precursor stoichiometry and local firing environment on the microstructural development of sol-gel derived lead zirconate titanate (PZT) thin films was investigated. Typically, excess Pb is added to films to compensate for PbO volatilization during heat treatment. Here, it is shown that the use of stoichiometric precursors with either a PbO atmosphere powder or a PbO overcoat during the crystallization heat treatment is an attractive and viable alternative method for control of film stoichiometry. Using these approaches, we have fabricated single phase perovskite thin films with microstructures and electrical properties (Pr ∼ 36 μC/cm2 and Ec ∼ 45 kV /cm) comparable to those of films using optimized solution chemistries and excess Pb additions. The potential advantage of increasing PbO partial pressure, or activity, during firing versus excess Pb additions is discussed from the standpoint of a proposed crystallization scenario based on the kinetic competition between Pb loss and the nucleation and growth rates of the perovskite phase.

Reversibility of the Perovskite‐to‐Fluorite Phase Transformation in Lead‐Based Thin and Ultrathin Films

“…[8,9] Since thin films deposited from the vapor phase or a liquid solution do not require the level of solid-state diffusion that powder-based techniques rely upon for chemical mixing and densification, they can be processed at significantly lower temperatures (typically 600-700 8C, [10,11] with some reports near 500 8C [12,13] ), which decrease PbO volatility. Reduced processing temperatures, however, are not sufficient to eliminate the problem of Pb volatility, as evidenced by the presence of a low-permittivity Pb-deficient fluorite phase on the top surface of films after crystallization.…”

“…Amorphous Pb-based films initially crystallize into an intermediate metastable disordered Pb-rich (and/or O-deficient) fluorite phase en route to the thermodynamically stable perovskite phase. [19][20][21][22] The large surface/volume ratio, reducing conditions associated with organic burnout, and flexible stoichiometry of the intermediate fluorite phase (which provides a lower barrier to PbO volatilization than the rigid perovskite stoichiometry) [11] are all believed to contribute to the loss of Pb at moderate temperatures in ultrathin films.…”

Study of (111)-oriented PZT thin films prepared by a modified sol–gel method

“…The obtained bigger grains may be due to lattice matching between the PZT film and Pt layer. According to the results of previous studies [10,29], we can conclude the growth process of the PZT films is that due to the lattice constants matching between PZT and Pt substrate, firstly the nucleation of perovskite phase on the Pt electrode surface, then the crystalline grain growth and finally the crystallization of the surface part of the film. Figure 4 shows the cross-sectional and surface images of 3-layered P 1.1 ZT thin films sintered at different temperature.…”

Ordered Mesoporous Thin Film Ferroelectrics of Biaxially Textured Lead Zirconate Titanate (PZT) by Chemical Solution Deposition

“…65 From this analysis, we find an atomic composition, zirconium is enriched at the top surface is not yet fully understood. 66 However, given that the PZT material employed here is solution-processed via dip coating as well as nanocrystalline and mesoporous, it seems also rather well-defined at the atomic level. fits to the data and the red curves correspond to the sum of the peak fits (the Shirley method was applied to subtract backgrounds).…”