Thermal decomposition kinetics and particle evolution characteristics of nano barium titanate precursor
Barium titanate has excellent properties such as high dielectric constant and low dielectric loss,and is the main raw material for preparing multilayer ceramic capacitors and other components.The thermal decomposition and gas precipitation characteristics of nano barium titanate precursor prepared by oxalate co-precipitation method were studied using a thermogravimetric-mass spectrometry analyzer,and the mechanism of thermal decomposition reaction of nano barium titanate precursor was revealed.The kinetic calculations were carried out using kissinger-akahira-sunose(KAS)method and flynn-wall-ozawa(FWO)method.The microstructure of the thermal decomposition products was observed using scanning electron microscopy(SEM),and the evolution mechanism of particles was analyzed.The results showed that the thermal decomposition process of nano barium titanate precursor could be divided into four weight-loss stages.The first stage was the release of water,the second stage produced CO and CO2,and the third and fourth stages produced CO2.Based on these results,the reactions involved in each stage were derived.As the heating rate increased,the maximum weight loss rate temperature corresponding to each weight loss stage moved towards the high-temperature zone.The fourth stage had the largest displacement towards the high-temperature zone,reaching 113℃.However,this stage had the fastest weight-loss rate and the reactions had been strengthened under the condition of 30℃/min.The FWO model was more suitable for describing the thermal decomposition process of nano barium titanate precursors.The average activation energies of the four stages were 67.89 kJ/mol,208.92 kJ/mol,494.04 kJ/mol and 195.11 kJ/mol,respectively.The activation energy of the third stage was the highest and the reaction was difficult to occur.During the thermal decomposition process of nano barium titanate,macroscopic large particles would evolve into aggregates of microscopic small particles.A higher constant temperature would lead to an increase in particle size.Therefore,the recommended constant temperature should not exceed 900℃.This research provided a theoretical basis for the selection of thermal decomposition process parameters for nano barium titanate precursors.
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维普
