Preparation Of BaCaV₂O₇ And NaMg₄V₃O₁₂ Materials

Micro-nano materials with special morphologies have attractive research value and huge application prospects in semiconductor,catalysis,electromagnetics,optics and other fields.BaCaV₂O₇ and NaMg₄V₃O₁₂materials as potential LTCC or ULTCC materials,their physical or chemical properties depend on their crystal phase,particle size and microscopic morphology,and these factors are affected by the preparation method.At present,high temperature solid phase method is the main preparation method.This method is not suitable to prepare micro-nano materials with less impurity and different morphologies at low temperature,and there are few reports on vanadate micro-nano materials with special morphologies.Therefore,by changing the preparation method,satisfactory crystal phase,particle size and micro morphology of BaCaV₂O₇and NaMg₄V₃O₁₂ micro-nano materials can be obtained,so as to realize the special function of the material and broaden the application range of the material,which is very important for the development of micro-nano technology.This paper mainly used sol-gel method and improved precipitation method to prepare BaCaV₂O₇ micro-nano material at low temperature,used the molten salt method to prepare NaMg₄V₃O₁₂ micro-nano material with octahedral morphology,and studied the crystal phase and microscopic morphology of the material by changing the preparation conditions.The main content of the paper includes:The sol-gel method and the improved precipitation method were used to prepare BaCaV₂O₇ micro-nano material at low temperature,and different test methods were used for characterization.The heating reaction process of the precursor,the crystal phase of the sample and the micro morphology of the material were studied.It was determined that both the sol-gel method and the improved precipitation method can prepare high-purity BaCaV₂O₇material at low temperature.By changing the preparation conditions of the sol-gel method,such as temperature,time,citric acid dosage and other factors,the optimal preparation conditions for obtaining the BaCaV₂O₇ sample with the best particle size are determined as follows:calcination temperature is 650oC,calcination time is 2 h,citric acid dosage is stoichiometric 1.5 times the ratio.And the improved precipitation method can be used to prepare BaCaV₂O₇ micro-nano material with smaller particle size.The sol-gel method and the molten salt method using NaNO₃-KNO₃ as the mixed molten salts were chosen to prepare NaMg₄V₃O₁₂ micro-nano material,the heating reaction process of the precursor,the crystal phase of the sample and the micro morphology of the material were studied,and it is determined that the mixed molten salt method can prepare high-purity NaMg₄V₃O₁₂ material at a low temperature of 400oC.By changing the preparation conditions,such as temperature,time,and the amount of molten salt,the optimal preparation conditions for obtaining the NaMg₄V₃O₁₂ material with an octahedral morphology and a particle size of 6-12μm are determined as follows:the calcination temperature is 450oC,the calcination time is 3 h,and the ratio of molten salt is 1:4.Finally,by changing the type of molten salt and selecting suitable reaction materials,the single-component KNO₃ and NaNO₃ molten salt methods were used to explore the preparation of NaMg₄V₃O₁₂ material with special morphology at low temperature.As a result,NaMg₄V₃O₁₂ material with octahedral morphology was prepared.Compared with the results of the NaNO₃-KNO₃ mixed molten salt method in the previous chapter,it is determined that the mixed molten salt method can reduce the calcination temperature of the NaMg₄V₃O₁₂material to a minimum of 400oC,and the octahedral morphology of the material prepared by the single-component NaNO₃ molten salt method is better.By changing the preparation conditions of the single-component NaNO₃ molten salt method,the optimal preparation conditions for obtaining the NaMg₄V₃O₁₂ material with complete octahedral morphology,good dispersibility,and particle size of 5-18μm are determined as follows:calcination temperature is 500oC,calcination time is 3 h,and molten salt dosage ratio is 1:4.