Preparation Of Spherical Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ By Coprecipitation Method Research On Electrical Properties Of Powders And Ceramics

Barium titanate,as an electronic ceramic raw material with excellent dielectric,ferroelectric and piezoelectric properties,is an essential material for developing high-end industries and enhancing the country's core technological strength.With the popularity of smart phones and the development of high-end technologies such as 5G communication equipment,ceramic electronic components have played a critical role in it.Therefore,people have put higher and higher requirements on the preparation technology and performance of barium titanate powder and ceramics.On the one hand,in order to broaden the temperature range and enhance the electrical properties of ceramics,barium titanate was modified by doping,and a batch of high performance materials such as barium zirconate titanate(BZT),barium titanate(BCT),barium zirconate titanate(BCZT)were designed.On the other hand,in order to accommodate the requirements of miniaturization and wearable materials,the high-end powders technology for the preparation of high purity ultrafine barium titanate has been studied extensively.The co-precipitation method is a kind of preparation method which can produce high purity and good uniformity nano-barium titanate powder,and it is widely used in practical production.However,it is easy to produce component segregation of barium titanate based products under multi-component system.Therefore,this paper will improve the reaction conditions for the preparation of barium titanate-based ceramic materials by co-precipitation method,and it is expected that barium titanate-based ceramic materials with controllable composition can be obtained and the electrical properties of ceramics can be enhanced.At last the reaction mechanism of coprecipitation method is discussed.The main research contents and results of this paper are as follows:1.BaTiO3,BaZr0.2Ti0.8O3,Ba0.7Ca0.3TiO3 and Ba0.85Ca0.15Zr0.1Ti0.9O3 powders and ceramics are prepared by using Ba(CH3COO)2,Ca(CH3COO)2·H2O,Zr(NO3)4·5H2O and TiCl4 as raw materials and NaOH as precipitant.It is studied systematically that the effects of ion substitution on the phase structure and morphology of the powders and ceramics.The powders are spherical particles with good dispersibility from 100 nm to 400 nm in average diameter,and BT and BZT ceramic materials are dense and stoichiometric.Through the analysis of the composition of BCT and BCZT materials,it is found that the Ca elements in the sample are seriously lost,and the actual composition of the sample deviates from the stoichiometric ratio,which leads to the appearance of other phases in the materials.A large number of pores are found in the ceramics,and the grains are not growing normally,which can not produce the dense ceramics.2.The co-precipitation reaction conditions with KOH as precipitant and K2TiO(C2O4)2·2H2O as raw materials were determined by changing the conditions of Ca(CH3COO)2·H2O input proportions and kinds of precipitant and titanium raw materials,which can effectively make the metal elements in the Ba0.7Ca0.3TiO3 precipitate together,and Ca is no longer lost.The best reaction conditions for the preparation of BCT stoichiometric sphere with good dispersion and uniform size with an average diameter of 417 nm are as follows:(Ba+Ca)/Ti molar ratio is 1.0,KOH concentration is 9 M,Ca(CH3COO)2 input proportions(?)is 0.85.Tetragonal BCT ceramics are sintered with this powders to obtain the best dielectric properties(?max=6723,tan?=0.011),ferroelectric properties(Pmax=22 ?C/cm2,breakdown field strength is 110 kV/cm)and energy storage properties(Wrec=0.45 J/cm3,?=43%)at a sintering temperature of 1380?.FT-IR and TG-DSC are utilized to analyze the changes of the substances during the reaction,and it is proved that potassium titanium oxalate can be used as a titanium source and can also precipitate Ca.The TEM analysis shows that the BCT powders are mixed phases,and the composition of the single spherical particles is evenly distributed.3.Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramic materials are prepared using Ba(CH3COO)2,Ca(CH3COO)2·H2O,Zr(NO3)4·5H2O and K2TiO(C2O4)2·2H2O as raw materials and KOH as precipitant.It is investigated that the effects of(Ba+Ca)/(Zr+Ti)molar ratio,KOH concentration,Zr(NO3)4 input proportions(?)on the phase structure,micro-morphology and product composition ratio of BCZT materials.It was found that under the conditions of(Ba+Ca)/(Zr+Ti)=1.0,CKOH=8 M and ?=0.61,we successfully obtained BCZT spherical powders with good dispersion and uniform size with an average diameter of 614 nm.The composition of products conforms to the stoichiometric ratio.Pure phase BCZT ceramics are sintered with these powders to obtain the best dielectric properties(?max=7588,tan?=0.016)at a sintering temperature of 1420?.BCZT ceramics are obtained the best ferroelectric properties(Pmax=15.92 ?C/cm2,breakdown field strength is 150 kV/cm)and energy storage properties(Wrec=0.54 J/cm3,?=71%)at a sintering temperature of 1440 ?.Through TEM and Raman spectra,the BCZT powders are analyzed as mixed phases of a tetragonal phase and orthogonal phase.The reaction process of preparing BCZT powders is analyzed by FT-IR and TG-DSC,and the reaction mechanism is deduced.