The subject of sol−gel electrochemistry is introduced, starting with a brief account of milestones in its evolution. Then, the types of sol−gel materials that are useful for electrochemistry are presented, followed by a description of recent advances in the various fields of sol−gel electrochemistry. Modified electrodes, solid electrolytes, electrochromic devices, and corrosion protection coatings are described. Emerging fields such as RuO2 supercapacitors and electrochemical synthesis of sol−gel precursors are also addressed.

Sol−Gel Materials in Electrochemistry

The paper presents short review of the works performed during the last few years in the field of the alkoxy-derived ferroelectric films. PZT films were prepared using titanium and zirconium alkoxides and Pb(CH3COO)2· 2H2O as precursors. Different way of lead acetate dehydration and the impact of lead excess in the precursor solutions on the properties of the PZT films are discussed. Trimetallic alkoxide systems Bi(OR)3-Ta(OR)5-ROH (R = Me, Et or i Pr) were studied as precursors for preparation of SrBi2Ta2O9 films. Films prepared from these solutions and annealed at the temperature between 700 and 750°C demonstrated the remanent polarization Pr* − P^r = 7–9 μC/cm2. Ba1-xSrxTiO3 films we applied from modified alkoxide solutions. Decomposition of the organic phase in the course of thermal treatment of the films is studied by IR-spectroscopy. The dependence of the dielectric permittivity of the films via the annealing temperature is reported. Preparation of LiNbO3, SrZr0.2Ti0.8O3, Zr0.8Sn0.2TiO4 is briefly discussed.

Sol-Gel Derived Ferroelectric Thin Films: Avenues for Control of Microstructural and Electric Properties

Tetragonal lead zirconate titanate thin films on platinized silicon wafers have been prepared from chemically different precursor solutions by chemical solution deposition. Literature known routes have been evaluated and an optimized standard process has been developed leading to Pb(Zr0.3,Ti0.7)O3 films with a high degree of (111) orientation which consequently shows square hysteris loops with Pr values of 34 μC/cm2. Other solvents, different alkoxides of the transition metals, and different carboxylates of lead have been systematically introduced in this standard process and their influence on the final morphological and electrical properties has been studied. It has been found that the use of lead (II) propionate and titanium tetra n-butoxide for solution synthesis leads to a decrease of the remanent polarization of ∼50%. Furthermore the reaction atmosphere after spinning and during the pyrolysis has been investigated. Increased ambient humidity after the spin coating process also caused a significant deterioration of the final film properties. The findings have been explained in terms of a hindered formation of the (111) texture promoting intermediate Pt
 x
 Pb phase.

Chemical modifications of Pb(Zr0.3,Ti0.7)O3 precursor solutions and their influence on the morphological and electrical properties of the resulting thin films

Metal halide perovskites have been demonstrated as one of the most promising materials for low-cost and high-performance photovoltaic applications. However, due to the susceptible crystallization process of perovskite films on planar substrates and the high sensitivity of the physical and optoelectronic nature of the internal interfaces within the devices, researchers in different laboratories still experience poor reproducibility in fabricating efficient perovskite solar cells with planar heterojunction device structures. In this methods paper, we present detailed information on the reagents, equipment, and procedures for the fabrication of planar perovskite solar cells in both “regular” n-i-p and “inverted” p-i-n architectures based on one-step solution-processed methylammonium lead triiodide (MAPbI3) perovskite films. We discuss key parameters affecting the crystallization of perovskite and the device interfaces. This methods paper will provide a guideline for the reproducible fabrication of planar het...

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Reproducible Planar Heterojunction Solar Cells Based on One-Step Solution-Processed Methylammonium Lead Halide Perovskites

Thin ferroelectric Pb(Zr0.48Ti0.52)O3 lead zirconate titanate films have been prepared on platinized silicon substrates via chemical solution deposition. The starting film-forming solutions were prepared by reacting lead acetate with Ti and Zr alkoxides in 2-methoxyethanol. The electrical properties of the films were shown to depend on the Ti and Zr alkoxide precursors used in synthesis. The nature of the zirconium alkoxide had the strongest effect on the properties of the films. The best properties were obtained with zirconium n-propoxide.

Role of precursors in the formation of lead zirconate titanate thin films

Different ways of dehydration of lead acetate trihydrate for its application in sol-gel techniques are discussed. Reaction of Pb(CH3COO)2·3H2O with acetic acid anhydride proved to be the most efficient way of its dehydration. Characteristics of the solutions of lead acetate in methoxyethanol dehydrated by different methods are presented. Solutions for preparation of PZT films are prepared using electrochemical dissolution of titanium and zirconium in methoxyethanol. Physico-chemical properties of these solutions alongside with structural and electrical characteristics of the PZT films obtained from these solutions are presented. The effect of lead content in solutions on the properties of the films obtained is discussed.

Alkoxy-derived ferroelectric pzt films: the effect of lead acetate dehydration techniques and lead content in the electrochemically prepared solutions on the properties of the films

Electrochemically prepared methoxyethoxide solutions have been suggested as precursors for sol-gel technology. Methoxyethoxides demonstrate higher stability in organic solvents than alkoxides; chelating properties of the ether oxygen cause considerable stability of methoxyethoxides to hydrolysis in comparison with the derivatives of aliphatic alcohols. This makes methoxyethoxides promising precursors for oxide synthesis. Methoxyethanol proved an exceptionally convenient solvent for electrochemical synthesis. The electrochemically prepared solutions demonstrate unique film-forming properties and were used for synthesis of the films of complex perovskites BaM11 1/3Mv 2/3O3 (M11 = Zn, Co, Ni; Mv = Nb, Ta), yttrium-stabilized ZrO2, PZT.

Anodic dissolution of metals in methoxyethanol—a way to new precursors for sol-gel technology

Preparation of complex oxides in the form of powders and thin films from metal alkoxides is discussed. Most attention is paid to ferroelectric and related materials - complex titanates and zirconates. Techniques for preparation of high-purity morphologically homogeneous powders Ti2, ZrO2 barium titanate and BaTiO3-based solid solutions, MgTiO3, Bi2WO6, Bi2MoO6 are proposed and discussed wilh respect to their application in ceramics technology. The solutions prepared electrochemically in methoxyethanol were widely used for formation of thin films, e.g. Y2O3-stabilized ZrO2 and PZT solid solutions on Pt-coated silicon substrates.

E. P. Kovsman

Papers

Alkoxy-derived ferroelectric pzt films: the effect of lead acetate dehydration techniques and lead content in the electrochemically prepared solutions on the properties of the films

Anodic dissolution of metals in methoxyethanol—a way to new precursors for sol-gel technology

Preparation of Powders and thin Films of Complex Oxides From Metal Alkoxides