Influence of chelation ratio of metal alkoxides on aging of PZT 53/47 sol-gel-based precursors

Abstract

The high reactivity of metal alkoxides, common starting reagents in sol-gel-based synthesis routes, generally demands the use of chelating agents in order to avoid fast hydrolysis and also to allow an easier manipulation of intermediates as well as final solutions. Under these conditions, stability issues sometimes can be linked to chelation issues that, therefore, should deserve a proper study suited to the material system of interest and, more specially, when considering the use of sol-gel-based precursors in research, small-scale applications and industry. In this work, we explore the sol-gel-based synthesis route of lead zirconate titanate (Pb(Zr 0⋅53 Ti 0⋅47 )O 3 or PZT 53/47) using acetylacetone-chelated propoxides as intermediate reactants. Our main purpose here is to analyse the influence of the alkoxides:acetylacetone chelation ratio on the time evolution of mean particle size in the resultant organic colloidal dispersion used as PZT precursor. Purposely, we explored three different scenarios for chelation: (i) defective chelation, (ii) optimal chelation and (iii) excessive chelation. The time dependence of mean particle size was recorded by dynamic light scattering (DLS) measurements and aggregation kinetics was then explored by considering a diffusion-limited colloidal aggregations (DLCA) model.

A ‘Universal’ Bottom-up Sol-gel Based Synthesis of Pzt (1-x)/x Submicrometric Structures: 1. Dynamic Light Scattering Characterization of Precursor Stability and Aggregation Kinetics

“…As has been reported before for different experiments 12,16 , there is a noticeable change in the size distribution curves as all our samples aged. At first, Figure 2a, as-prepared sols featured multimodal distributions with a noticeable percentage of particles that could even have sizes sometimes above 1 μm.…”

“…First, lead acetate is dissolved in acetic acid with a 1:3 molar ratio at 120 °C for 3 hours in order to form solution A and, in a second step, a solution B is obtained when stoichiometric amounts of zirconium and titanium propoxides were mixed with acetylacetone at the optimal chelation ratio (R OPTIMAL ) that, as shown in an earlier work 16 , is dependent on the chosen Zr/Ti ratio and is ideally given by R optimal (x) = 2(2 -x) according to the reaction: …”

Overviews of Synthesis of Nanomaterials

“…When the metal alkoxide precursors are used, the sol is formed by the following hydrolysis: M(OR) 4 þ nH 2 O / M(OR) (4Àn) (OH) n þ nHOR [42]. The hydrolysis can be simplified as a general reaction: M þ þ nH 2 O / M(OH) n þ nH þ .…”

The Sol-Gel Method: Pathway to Ultrapure and Homogeneous Mixed Metal Oxide Nanoparticles

“…They called alkoxides and oxo-alkoxides as "single source precursors" for preparation of mixed metal oxide. Kapoor et al [73,74] as well as other researchers [75][76][77][78] also prepared mixed metal oxide using alkoxides or oxo-alkoxide precursor.…”

“…Precipitation during hydrolysis results due to high reactivity of alkoxides towards water which can be prevented by slowing down the hydrolysis process. This can be done by carrying out ligand exchange reaction [50,53,78]. In ligand exchange reactions, alkoxy group is replaced either by sterically more crowded group (such as 2-methoxyethanol, tert-amyl alcohol, tert-butyl alcohol, etc.)…”