Piezoelectric PZT nanodevices
from a hybrid ligand burning method
Lorenzo Tattini, Pierandrea Lo Nostro*, Andrea Ravalli, Manuela Stirner,
Massimo Bonini, Piero Baglioni
Department of Chemistry and CSGI, University of Florence, via della Lastruccia 3, 50019 Sesto Fiorentino (Firenze) – Italy
Electronic Supplementary Information
Table of Contents:
Synthesis
Figures
Synthesis. The “standard alkoxides” approach is resumed in Scheme S1. The same general procedure was used to prepare solutions containing Ti(IV) or Zr(IV) and the ligand. The proper amount of the selected ligand was dissolved in water to obtain a 6 M solution. The alkoxide was then added at 40 °C under magnetic stirring. In order to avoid hydrolysis and condensation of the metal complexes, ligands were used in excess, and solutions were added slowly. Catalytic amounts of H2O2 were added to the ligand solution to enhance the formation of the carboxylic complexes. The concentrations of the ligand and of the metal ion in the final solution were 2 M and 0.8 M, respectively. Lead nitrate was dissolved in a solution of EDTA with an equimolar ratio Pb(II):EDTA. A catalytic amount of ammonium hydroxide (100 µL) was added. The final concentration of the Pb(II)-EDTA complex was 1.6 M.
Proper amounts of the cations solutions were mixed, heated in a flask at 80 °C with a heating mantle and the solvent evaporated. The temperature of the heating mantle was raised. As soon as the burning process started, the heating treatment was stopped. The combustion of the organic ligands brought about the evolvement of large amounts of dark brown gases. A gray, fine-grained precursor powder was obtained.
A flowchart of the “EDTA method” is reported in Scheme S2. 5 g of titanium isopropoxide were added to 10 mL of acetic acid. The proper amount of zirconium propoxide was added in the mole ratio Ti(IV):Zr(IV) = 48:52. Lead acetate was dissolved in a small amount of water, the concentration of Pb(II) was equal to the overall concentration of Ti(IV) and Zr(IV). The water and acetic acid solutions were mixed quickly, and finally EDTA was added in equimolar amount with respect to the total cations. Upon shaking, the solution became clear, and water was evaporated by heating. After drying, the ligand was burned, and the heating was stopped as soon as the combustion gases started developing. On the basis of the DTG data obtained for sample E (Table 1), and of the characterization of the samples obtained from precursors A, B, C, and D, the precursor powder was finally calcinated for 15 min at 450 °C.
In order to verify the molar ratio that corresponds to the best electro-mechanical properties, two additional samples, with Ti(IV):Zr(IV) mole ratios of 25:75 and 75:25 were prepared according to the same procedure.
The “oxides” approach is shown in Scheme S3. Lead nitrate was dissolved in an ammoniacal solution of EDTA (PbII:EDTA = 1:1). Titanium and zirconium oxides were separately dispersed in a tartaric acid solution (2 M), keeping the temperature of the solution at 40 °C, under magnetic stirring. The concentration of Ti(IV) or Zr(IV) cations was approximately 0.8 M. A white dispersion was obtained. Proper amounts of each dispersion were mixed. The solution containing all the cations was heated in a heating mantle until the solvent was completely evaporated following the same procedure adopted for the “EDTA method”. As the evaporation was completed a fluffy material was obtained. The temperature was raised and as the burning process started the heating treatment was stopped.
The precursors obtained from both “oxide” and “standard alkoxides” syntheses were calcinated in a muffle furnace at 400 °C, 600 °C and 750 °C. The calcination step was performed for 1 h, 2 h and 4 h, with a heating rate of approximately 15 °C/min. In order to accelerate the combustion of the carbonaceous residues in the powders precursors, during the process a gentle air flow was forced into the muffle furnace.
Figures
Scheme S1. Synthesis from alkoxides.
Scheme S2. Synthesis from alkoxides with EDTA.
Scheme S3. Synthesis from oxides.
Figure S1. DLS normalized autocorrelation function.
Figure S2. Electrical response of a 52:48 powder calcinated from precursor D.
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