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BTO nanoparticles synthesis

Barium titanate (BTO) is used as high-k dielectric phase in multi-layer ceramic capacitors (MLCC). A report prepared by Sandia National Laboratories lists three different syntheses for BTO nanoparticles.
The first synthesis is using Lanthanum-Doped Lead Zirconium Titanate (PLZT) developed at Sandia. In the reaction, metal salts are dissolved in a solution of nitric acid and water. After stirring overnight, titanium isopropoxide (Ti(OPr)4) and a solution of polyvinyl alcohol (PVA) in water are added. Finally, the acidic aqueous solution is boiled off, decreasing the solubility of the dissolved metals and leading to particle formation. The PVA forms a semi-dilute solution which limits the final particle size.
Barium nitrate
To synthesize BTO, barium nitrate was the only metal salt required. The synthesis was attempted both with equal moles of barium and titanium and a 20% excess of barium to aid final BTO formation. At room temperature, the product of all reactions was amorphous. After a post anneal of 700 °C a mixed phase product was formed. Post-annealing at 1000 °C was required to fully convert the particles synthesized via this method to crystalline BTO.
Barium acetate
The second synthesis is by using barium acetate and titanium tert-butoxide as precursors. A mixture of ethylenediamine (EDA) and ethanolamine (MEA) were used as the solvent. These solvents have a basic pH and can catalyze room temperature formation of crystalline BTO. The amine functionality of these solvents also allows them to bind to the BTO surface and act as ligands. Size of the particles can be controlled by varying the EDA:MEA ratio. In addition to repeating the EDA:MEA ratio of 1:1 as in the literature, the reaction time of the 1:1 ratio sample was increased to 96 hrs. (the longest reaction time reported in the literature was 48 hrs.), and larger particles were produced as desired.
Barium hydroxide hydrate
The third synthesis is by using barium hydroxide hydrate (Ba(OH)2•8H2O) as a reagent along with titanium isopropoxide. The entire reaction was performed in a solvent of isopropanol at a temperature of 80 °C. Although this is higher than room temperature it is still a low enough reaction temperature such that mass production of cheap particles would not be precluded.
Following the procedure described in the literature, the particles were synthesized without the addition of any water. However, this resulted in predominantly amorphous particles. Yoon and coauthors reported that the water molecules available from the Ba(OH)2•8H2O provided enough water for the reaction between the barium ions and titanium isopropoxide to move forward.
When the reaction was repeated using 6 mol of water and this time the reaction produced cubic BTO nanoparticles.

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