Preparation Of Nano-sized Yttrium Oxide Powder By Carbonate Precipitation Method

Nano-yttrium oxide have excellent properties of both nanomaterials and rare earth oxides,and are widely used in catalyst,fluorescence,waveguide,magnetism and coating fields.In view of the problem that oxalate and ammonium ions will be produced in the preparation process of traditional liquid precipitation method,this paper used carbonate as precipitator to prepare nano-yttrium oxide,and carried out the selection of precipitation process,drying method,thermal analysis,kinetics and roasting process.The main results obtained are as follows:Nano Y₂O₃was prepared with yttrium chloride as raw material and sodium carbonate and sodium bicarbonate as precipitant.The effects of different feeding methods,concentration of Y³⁺,concentration of sodium carbonate,mole ratio of Y³⁺to sodium carbonate,stirring speed,precipitation temperature,precipitation time,amount of surfactant and composition of precipitator on the morphology,agglomeration and particle size of precursor powder were investigated.The results show that under the condition of positive feeding,Y³⁺concentration is 0.1 mol/L,the volume fraction of precipitant is 10%sodium carbonate and 90%sodium bicarbonate,and the mole ratio of Y³⁺concentration to sodium carbonate concentration is 1:1.575,precipitation temperature of 30℃,feeding speed of 10 ml/min,stirring speed of 300r/min,under the conditions of no aging,relatively ideal yttrium oxide precursor can be prepared.In order to explore the effect of drying methods on yttrium oxide precursor agglomeration,direct drying,freeze drying and alcohol washing drying were used to study.The results showed that the precursors obtained by direct drying had smaller particle size and more uniform particle size.On this basis,the experiment also explored the effect of spray drying,the results show that:under the conditions of spray drying temperature of 150℃,peristaltic pump speed of 30%,the preparation of yttrium oxide precursor powder(D₉₀-D₁₀)/2D₅₀=0.46,smaller particle size,more uniform particle size distribution.The composition of yttrium oxide precursor is Y（OH）x（CO₃）y·z H₂O by Fourier transform infrared spectroscopy（FI-IR）.The thermal decomposition of Y（OH）x（CO₃）y·z H₂O can be divided into two stages by TG-DTA and XRD.In the first stage,Y（OH）x（CO₃）y·z H₂O loses one water of crystallization and generates Y（OH）CO₃at 213℃.In the second stage,between 213℃and 613℃,a 1/2 H₂O and a CO₂are lost to form Y₂O₃.Therefore,the composition of yttrium oxide precursor was determined to be Y（OH）CO₃·H₂O.It is calculated by Kissinger’s method,Ozawa-Flynm-Wall method,Crane equation and Coats-Redfem equation:The apparent activation energy E of the first stage thermal decomposition of basic yttrium carbonate（Y（OH）CO₃·H₂O）ranges from 60.1008 to 90.2306 k J·mol^-1,the pre-exponential factor A=7.46169×10⁵,and the reaction order n=0.74.The apparent activation energy E of the pyrolysis of Y（OH）CO₃to Y₂O₃in the second stage is 220.2733 k J·mol^-1,the pre-exponential factor A is 5.3986×10¹⁰,and the reaction order n=0.82.It is controlled by Avrami Erofeev equation,and the corresponding decomposition function integral is g（α）=[-ln（1-α）]⁴.On the basis of the above work,the effects of different calcination temperature,heating rate and holding time on the morphology,morphology and particle size of yttrium oxide were investigated experimentally.The results show that the morphology of precursor and calcined product yttrium oxide is similar,under the conditions of calcination temperature of 860℃,heating rate of 5.375℃/min,holding time of 1 h,D₅₀=0.050 um,(D₉₀-D₁₀)/2D₅₀=0.98,good dispersion of nano Y₂O₃.