Microstructural development and electrical properties of sol-gel prepared lead zirconate-titanate thin films

Abstract

A systematic investigation of the microstructural evolution of fast fired, sol-gel derived Pb(Zr, Ti)O3 films (Zr/Ti = 54/46) was performed by analytical transmission electron microscopy (TEM). It was found that the nucleation and growth of the sol-gel PZT films were influenced by the precursor chemistry. The precursor solution was composed of Pb 2-ethylhexanoate, Ti isopropoxide, and Zr n-propoxide in n-propanol. Porous and spherulitic perovskite grains nucleated and grew from a pyrochlore matrix for NH4OH-modified films, but no chemical segregation was found. These thin films consisted completely of porous spherulitic PZT grains (∼2 μm) when the firing temperature was increased. Chemical phase separation with regions of Zr-rich pyrochlore particles separated by Zr-deficient perovskite grains was observed in the initial stages of nucleation and growth for CH3COOH-modified PZT films. This phase separation is attributed to the effect of acetate ligands on the modification of molecular structure of the PZT precursor. Firing the acid-modified films at higher temperatures for long times resulted in porous perovskite grain structures. The residual porosity in these films is suggested to be a result of differential evaporation/condensation rates during the deposition process and the gas evolution at high temperatures due to trapped organics in the films. Dielectric and ferroelectric properties were correlated to the microstructure of the films. Lower dielectric constants (∼500) and higher coercive fields (∼65 kV/cm) were found for the acid-modified PZT films with phase separation in comparison to those measured from the sol-gel films with a uniform microstructure (∽ > 600, Ec < 50 kV/cm). All films fired at 650 °C showed relatively good remanent polarization on the order of 20 μC/cm2.

A Study on the Microstructure of Preferred Orientation of Lead Zirconate Titanate (PZT) Thin Films

“…Earlier studies on the fabrication of PZT thin film using the sol-gel method mainly concentrated on the transformation of the amorphous gel film to the perovskite phase during annealing. 2,[5][6][7][8][9] Recently, many studies on the control of the preferred orientation of the PZT films on various substrates have been reported because the preferentially oriented or epitaxial films show better electrical properties: the P-E hysteresis and the pyroelectric coefficient. 1,2 Since the nucleation is the rate-limiting step in the perovskite transformation, the creation of numerous heterogeneous nucleation sites is important to achieve the perovskite phase formation.…”

“…The films were fabricated with different coating cycles (3,5,7,9,11), dried at 330 ± C for different holding times (5, 30, 60 min), and then annealed at the same temperature of 650 ± C using rapid thermal annealing (RTA). Effects of the holding time for pyrolysis and the coating cycle on the preferred orientation of the PZT thin films were studied.…”

The influence of water of hydrolysis on microstructural development in sol-gel derived LiNbO3 thin films

“…1 " 3 Thin films of LiNbO 3 are of current research interest because of the demand for active integrated optical devices. 10 " 12 It has also been shown that the structure of sol-gel derived LiNbO 3 thin films sensitively depends on the prior processing. 7 " 9 Processing parameters such as solution chemistry, deposition technique, firing conditions, and substrate are known to influence the development of film crystallinity, porosity, grain size, and growth morphology during solgel processing.…”

Thick films fabricated by laser ablation of PZT microparticles

“…Repeated depositions followed by firing at elevated temperature are required to prepare thick films using these processes. Furthermore, sol-gel processing and screen-printing require high post-deposition processing temperatures to anneal the films to achieve the perovskite crystal structure [5,6]. The high processing temperature limits the overall film thickness because of cracking caused by thermal expansion mismatch with the substrate.…”