【作者】 彭秧锡；

【导师】 陈启元；

【作者基本信息】 中南大学 ， 应用化学， 2010， 博士

【摘要】 钛酸钡(铅)等纳米钛酸盐粉体及其固溶体是重要的电子陶瓷材料,近年来无论在理论上还是在技术应用上,都得到了广泛的关注。钛酸钡等电子陶瓷制备工艺中的一个基本特点就是以粉体为原料经成型和烧结而形成多晶陶瓷体,陶瓷粉体的质量直接影响最终产品的质量,所以研制钛酸钡等陶瓷电子器件的首要问题是制备出符合产品性能要求的粉体原料。因此,开展对钛酸钡(铅)等纳米粉体新的合成方法、制备反应机理、相转变规律等的研究仍然具有重要的理论与现实意义。论文详细评述了钛酸钡(铅)等电子陶瓷粉体的研究现状,并以BaTiO3、PbTiO3、Ba(ZrTi)O3、Pb(ZrTi)O3为研究对象,系统地开展了合成方法、相变及反应机理、掺杂改性等应用基础研究。1、研究并提出了过氧化物前驱体热分解法制备纳米钛酸钡新的可能反应过程(机理)。以H2TiO3、氨水、过氧化氢和水溶性钡盐为原料,采用过氧化物前驱体热分解法制备得到了纳米钛酸钡粉体,其中600℃煅烧1h得到立方相钛酸钡,粉体粒径在20-40nm,1000℃煅烧lh得到四方相钛酸钡,粉体粒径在60-100nm。同时,加热该钛酸钡(钙、锶)过氧化物前驱体会有氧气产生,结合TG-DSC、电子能谱等实验分析,证实过氧化物前驱体热分解法制备纳米钛酸钡的反应过程(机理)为：H2TiO3+2H2O2+2NH3→(NH4)2Ti(H2O2)2O3(NH4)2Ti(H2O2)2O3+Ba2+→BaTi(H2O2)2O3↓+2NH4+BaTi(H2O2)2O3→(BaTiO5+2H2O)→BaTiO3↓+2H2OT+O2↑2、研究了掺杂(锶)诱导钛酸钡的相变规律。利用过氧化物前驱体热分解法可以制备得到纳米钛酸钡粉体,制备过程中掺入少量的锶,使得锶离子均匀进入母体晶格,会使相变温度明显下降,当加入摩尔比2%以内的锶离子后,相变温度由原来的900℃-1000℃降低到了800℃-900℃之间。当加入摩尔比5%以上的锶离子时,即使升高温度也难以发生相变,且高温下粉体还会发生分解。这与其晶体结构中钛离子的空间位阻有关系。当半径小的离子对钡离子进行部分取代,会使得晶体结构发生变化,钛离子空间位阻变小,振动容易,钛酸钡晶体由立方相转变为四方相的相变温度会降低；但当更多的钡离子被半径小的离子取代以后,钛离子的空间位阻将变得更小,钛离子上下振动均十分容易,此时反而难以实现其四方相的转化。当温度改变时,钛酸钡晶体TiO6八面体结构中Ti离子可能发生中心偏移,可形成一个具有稳定的Ti-O键的长五配位重排结构,此结构中Ti-O键长比六配位结构中更长,从而使Ti离子可以稳定存在,最终导致钛酸钡由稳定的立方相逐步转变为亚稳态的四方相。同时,掺入适量锶离子可以明显降低钛酸钡发生相变的晶粒尺寸,钛酸钡由立方相转化为四方相的晶粒尺寸在33nm附近(实验计算值)。3、采用凝胶燃烧法制备了BaTiO3、BaZr0.1Ti0.9O3纳米粉体。以偏钛酸、双氧水、氨水、硝酸钡等为原料,采用凝胶燃烧法制备得到了纳米BaTiO3粉体,并且通过控制前驱体的煅烧温度可以分别制得立方相或四方相的钛酸钡纳米粉体。在800℃煅烧钛酸钡前躯体4h,得到含有少量BaCO3杂质的立方相纳米BaTiO3粉体；当煅烧温度升高至1000℃时,可制得四方相纳米BaTiO3粉体,所得四方相BaTiO3纳米粉体的粒径在60-120nm。改变原料,同样方法制备得到了锆钛酸钡(BaZr0.1Ti0.9O3)纳米粉体,该粉体的粒径在30-80nm。4、研究并提出了PbTiO3、PbZr0.52Ti0.48O3粉体新的燃烧制备方法。以H2TiO3、H2O2、Pb(CH3COO)2·3H2O等为原料,EDTA、柠檬酸为配位剂和燃烧剂,先制备PbTiO3前驱体粉体,再在700℃煅烧该粉体1h,可制得PbTiO3纳米粉体,该粉体粒径为50-80nm。改变原料,同样方法制备得到了立方相PZT(PbZr0.52Ti0.48O3)粉体,该粉体粒径在100-200nm。该方法原料易得,成本低廉,工艺简单,生产条件容易控制,可为其它钛酸盐粉体的制备提供参考。5、以偏钛酸、双氧水、氨水、乙酸铅、乙酸锌和硝酸镁为原料,EDTA、柠檬酸为配位剂和燃烧剂,采用凝胶-燃烧法制备得到了PZNT和PMNT粉体。实验结果表明：PZNT约在488-527℃形成稳定化合物,在700℃煅烧其胶状前躯体2h后所得到的PZNT粉体的粒径在50-150nm；PMNT约在514-545℃形成稳定化合物,在800℃煅烧其胶状前躯体2h后所得到的PMNT粉体的粒径在100-300nm。6、以偏钛酸、双氧水、氨水、硝酸锂为原料,柠檬酸为络合剂和燃烧剂,采用凝胶燃烧法制备得到了Li4Ti5O12(LTO)亚微米粉体。首先,按摩尔比将H2TiO3溶于H2O2和NH3·H2O的混合溶液中,再加入适量柠檬酸,得到棕红色透明溶液,然后向该溶液中加入等摩尔的Li+溶液,再将此混合溶液加热浓缩成胶状物后在高温下煅烧,可以制得Li4Ti5O12亚微米粉体。研究结果表明：Li4Ti5O12约在450℃反应形成,将所得胶状物(前躯体)在800℃煅烧2h,制得的Li4Ti5O12粉体的粒径在200-300nm。更多还原

【Abstract】 Nano-titanate powder of barium (lead) titanate and its solid solution is an important electronic ceramic material. It has been focused on the theory and technical application in recent years. During the preparation processes of barium titanate, the fundamental characteristic is that polycrystalline ceramics were prepared from powder, followed by molding and sintering. The quality of ceramic powder has direct influence on the resultant products. So the preparation of powder which meets the requirements of product’ properties is the key problem for preparing electronic ceramic devices such as barium titanate. Therefore, it has great theoretical and practical significance in studying the problems such as new method of synthesizing, the mechanism of reaction, and the rule of phase transformation for nano-powder of barium titanate.The research status of electronic ceramic powder such as barium (lead) titanate etc. was reviewed detailedly in this study. And the applied fundamental researches of the synthesis method, phase transformation & reaction mechanism and doping modification etc. were carried out systematacially with BaTiO3, PbTiO3, Ba(ZrTi)O3 and Pb(ZrTi)O3 as the research objects.1. The reaction process (mechanism) of preparing nano-barium titanate by using peroxide precursor thermal decomposition method was studied and presented. Taking H2TiO3, ammonia water, hydrogen peroxide and water-soluble barium salts as raw materials, nano-barium titanate powder was prepared using peroxide precursor thermal decomposition method, in which cubic phase barium titanate with grain sizes between 20 and 40 nm were obtained by calcining at 600℃for 1 hour, and tetragonal phase barium titanate with grain sizes between 60 and 100 nm was obtained by calcining at 1000℃for 1 hour. Meanwhile, oxygen was produced when heating the peroxide precursors of barium (calcium and strontium) titanate. By combining experimental analysis of TG-DSC and electron spectrum etc., the reaction process (mechanism) of preparing nano-barium titanate using peroxide precursor thermal decomposition method was proved to be:H2TiO3+2H2O+2NH3→(NH4)2Ti(H2O2)2O3 (NH4)2Ti(H2O2)2O3+Ba2+→BaTi(H2O2)2O3↓+2NH4+BaTi(H2O2)2O3→(BaTiO5+2H2O)→BaTiO3↓+2H2O↑+O2↑2. The phase transformation law of (strontium) doping induced barium titanate was studied. Nano-barium titanate powder was prepared by using peroxide precursor thermal decomposition method. A small amount of strontium was added during preparation process, and the strontium ions were allowed to enter into the crystal lattice of mother substance evenly which obviously caused the phase transformation temperature to be reduced. After adding molar ratio of strontium ions less than 2% among the total cation, the phase transformation temperature was changed from 900℃-1000℃to 800℃-900℃. After adding molar ratio of strontium ions more than 5%, phase transformation was hard to occur even if the temperature was increased, and the powder would be decomposed at high temperature. This was related to the steric hindrance of titanium ions in the crystal structure. When the barium ions were replaced partially by ions with smaller radius, the crystal structure of the barium titanate would change, and the steric hindrance of titanium ion became smaller, the vibration became easier, and the phase transformation temperature of barium titanate crystal from cubic phase to tetragonal phase would be reduced; However, when more barium ions were replaced by ions with smaller radius, the steric hindrance of titanium ion became even smaller, and the up & down vibration of titanium ion was very easy. Therefore, the transformation of tetragonal phase was hard to occur. When the calcination temperature was changed, the structure of barium titanate crystal was transformed. Therefore, the Ti ions in the octahedral structure became eccentric (off-centering) and formed a pentacoordinate rearranged structure with stable Ti-O bond, where Ti-O bond length was longer than that in hexacoordinate structure, and so that the Ti ions would exist stably. Eventually, barium titanate would transform from the stable cubic structure to the metastable tetragonal structure.Meanwhile, the grain sizes that phase transformation of barium titanate occurred were reduced greatly by mixing an amount of strontium ions. The experiment results indicated that, the grain sizes which barium titanate transformed from cubic phase to tetragonal phase were around 33nm (calculated value from experiments).3. This study explored and proposed a preparation method of nano powder of BaTiO3 and BaZr0.1Ti0.9O3 by a gel-combustion method for the first time. Nano-BaTiO3 powder was prepared by taking the metatitanic acid, hydrogen peroxide, ammonia water and barium nitrate etc. as raw materials and using organic coordination compound combustion method. And nano-barium titanate powder with cubic phase or tetragonal phase was prepared respectively by controlling the calcining temperature of the precursor. Cubic phase nano-BaTiO3 powder with little BaCO3 impurity was prepared by calcining the precursor of barium titanate at 800℃for 4 hours; while calcining temperature increased to 1000℃, tetragonal phase nano-BaTiO3 powder would be prepared. The grain sizes of the prepared tetragonal phase nano-powder of BaTiO3 were between 60 and 120 nm with average grain size of approx.80nm. By changing the raw materials, nano-powder of barium zirconate titanate (BaZr0.1Ti0.9O3) was prepared by using the same method, with the grain sizes between 30 and 80 nm and the average grain size at approx 50 nm.4. A new combustion preparation method for nano-powder of PbTiO3 and PbZr0.52Ti0.48O3 was studied and presented for the first time. Taking the H2TiO3, H2O2 and Pb(CH3COO)2·3H2O etc. as raw materials, and EDTA and citric acid as complexing agent and fuel agent, precursor powder of PbTiO3 was prepared firstly, then by calcining the powder at 700℃for 1 hour, nano-powder of PbTiO3 was prepared with the grain sizes between 50 and 80 nm and average grain size at approx.70 nm. By changing raw materials, cubic phase powder of PZT (PbZr0.52Ti0.48O3) was prepared by using the same method, with the grain sizes between 100 and 200 nm and average grain size at approx.100 nm. This method, with extensive sources of raw materials, simple process, low cost and easy control of production conditions, is a good reference for preparation of other titanates nano-powder.5. PZNT and PMNT nano-powders were prapared by a gel-combustion method using meta-titanic acid, hydrogen peroxide, ammonia, zinc acetate, lead acetate and magnesium nitrate as raw materials, EDTA and citric acid as complexing agent and incendiary agent seprarately. The results showed that PZNT and PMNT were prapared through the obtained jelly being calcined at 488-527℃and 514-545℃, and the obtained jelly being calcined at 700℃for 2h, the grain sizes of obtained nano-powder of PZNT was 50-150nm, the average diameter of the particles was about 100nm, and the obtained jelly being calcined at 800℃for 2h, the grain sizes of obtained nano-powder of PMNT was 100-300nm, the average diameter of the particles was about 200nm.6. Li4Ti5O12 submicron-powders were prepared through Gel-combustion method with Citric acid as Complexing and fueling agent, and Titanic hydroxide, hydrogen peroxide, ammonia and lithium nitrate as the starting materials. Firstly, H2Ti03 was dissolved in the mixture of H2O2 and NH3·H2O at certain molar ratio, and some citric acid was added to obtain a orange-red transparent solution which then was added with identical mole of Li+solution.The obtained mixture was heated and condensed into jelly before calcined at different temperatures, and micro-powder of Li4Ti5O12 was fabricated. Investigations based on XRD, TG-DTA, TEM and IR show that LTO was fabricated at about 450℃. With the obtained jelly being calcined at 800℃for 2h, the grain sizes of obtained submicro-powder of Li4Ti5O12 was in the range of 200-300nm, respectively.更多还原