I have encountered precipitation issues during the sol-gel synthesis of La2NiO4. Initially, I prepared stock solutions of lanthanum nitrate hexahydrate, nickel nitrate hexahydrate, and citric acid in deionized water (500 rpm, 80°C). The combined solution, with a ratio of 2:1:1.5, was stirred at room temperature. While stirring, I introduced urea for pH regulation. However, at pH 4 (using 12.3g of urea), precipitates formed, and these precipitates are soluble in DI water. What steps can I take to address this and optimize the synthesis process?"
Hina Ahmad
The nickel ion may form a complex with urea, which will interfere with your experiment. Replace urea with lye to maintain pH.
Article Synthesis and X-ray diffraction study of some nickel(II) com...
Hina Ahmad Unexpected precipitation in La2NiO4 sol-gel synthesis can be caused by rapid pH change, premature hydrolysis, and an incorrect citric acid ratio. To optimize the synthesis, add urea gradually while monitoring pH with a meter, lower the initial temperature to minimize premature hydrolysis, refine the citric acid ratio, experiment with different La:Ni:citric acid ratios, use alternative chelating agents like tartaric or malic acid. If precipitates persist, gently filter and wash with DI water to remove soluble impurities while maintaining the desired gel.
Replace urea with lye (sodium hydroxide or potassium hydroxide) for pH control and avoid nickel-urea complexation.
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