Engineered Low Temperature Hydrothermal Synthesis of Phase-Pure Lead-Based Perovskites Using Ethylenediamine Tetra-acetic Acid Complexation

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Thermodynamic modeling of hydrothermal solutions was used to examine the influence of ethylenediamine tetra-acetic acid (EDTA) on the synthesis of lead-based perovskites, PbTiO 3 and PbZr 0.52 Ti 0.48 O 3 . Temperature, pH, input reagent concentrations, and Pb/(Ti + (Zr)) and Pb/EDTA ratios were examined. Thermodynamic calculations from 25 to 100 °C indicated that, when the Pb/EDTA and Pb/(Ti + (Zr)) molar ratios were 2.0 and Pb input concentration was 0.1 m, phase-pure perovskites formed across the greatest pH range (7−14+). Precipitation of unwanted unary lead phases such as PbO was suppressed in all cases. In the absence of EDTA and solutions containing a molar excess of lead ions, the formation of phase-pure perovskites was limited to narrow pH ranges (5−8 and above 14) because of PbO precipitation. Theoretical predictions were experimentally validated with use of X-ray diffraction, transmission electron microscopy, energy dispersive spectrometry, and atomic absorption spectroscopy. Experimental results validated the theoretical predictions at temperatures above a minimum reaction temperature. Relative to comparable hydrothermal systems free of EDTA, the addition of EDTA was found to lower the minimum reaction temperature by 70 °C for PbTiO 3 (70 °C) and 25 °C for PbZr 0.52 Ti 0.48 O 3 (125 °C).