锆钛酸铅（PZT）及钛酸镧铋（BLT）的纳米粉体和一维纳米结构的合成、表征及其机理的研究
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摘要
首先介绍了Pb(Zr_xTi_(1-x))O_3(PZT)和Bi_(4-x)La_xTi_3O_(12)(BLT)的结构、性能,并对PZT的准结晶学相界(MPB)、以及钙钛矿相PZT和铋层钙钛矿结构BLT相的合成方法进行了详细的综述和讨论;然后,回顾了—维纳米结构的研究进展,详细综述了—维纳米结构的生长机制和合成方法,并对BaTiO_3和PZT等钙钛矿结构铁电氧化物—维纳米结构的合成及性能研究进展进行了概述和分析。结合部分草酸盐固相反应法对共沉淀法合成PZT进行改进,探索并开发了实现纯相PZT低温合成的两步沉淀法。利用聚乙烯醇(PVA)对前驱体沉淀物团簇的隔离作用,辅助两步沉淀法合成出分散良好的PbZr_(0.52)Ti_(0.48)O_3(PZT)纳米粉体。首次利用共沉淀法实现了铋层钙钛矿结构相Bi_(3.25)La_(0.75)Ti_3O_(12)(BLT)纳米粉体的合成。开拓性地在水热系统中引入聚合物(聚乙烯醇(PVA)和聚丙烯酸(PAA)),合成出四元钙钛矿氧化物PbZr_(0.52)Ti_(0.48)O_3(PZT)四方相单晶纳米棒、纳米线和多晶纳米管。
采用差热和热失重分析(DTA和TG)对合成PZT和BLT粉体的前驱体粉体的热行为进行了分析,利用X射线衍射(XRD)探讨了PZT、BLT晶相演化与煅烧温度的关系,场发射扫描电子显微镜(FESEM)观察了合成粉体的形貌随煅烧温度的演化过程,电感耦合等离子体发射光谱(ICP)和电子探针X射线显微分析(EDX)对合成的PZT、BLT粉体的化学组成进行了分析,并结合TG分析了PZT粉体的热稳定性。
共沉淀合成PZT粉体的过程中,除形成主晶相钙钛矿PZT外,还形成少量的PbO相,导致高温煅烧的粉体Pb含量减少,偏离设计组成;低温煅烧的粉体,热稳定性较差。对共沉淀法改进后发展的两步沉淀法和部分草酸盐共沉淀法,强化了Zr~(4+)、Ti~(4+)离子的结合,形成特殊的前驱体粉体微观结构,避免了PbO的挥发,不仅实现了钙钛矿相PZT的直接合成,保持了很好的设计组成,而且所得到的粉体具有良好的热稳定性。
对不同方法制备的前驱体粉体形成PZT相的活化能研究显示,不论是共沉淀法,还是改进后的部分草酸盐共沉淀法或两步沉淀法合成钙钛矿相PZT的反应均遵循连续反应机制,即
Amorphous Precursor Powder→Pyrochlore→Perovskite PZT,反应物首先反应生成焦绿石相,然后再转化为钙钛矿相。
建立了两步沉淀法合成钙钛矿相PZT的模型。在PbO和ZT反应合成PZT相过程中,形成PbO-PZT和PZT-ZT两个界面,Pb~(2+)离子扩散到PZT-ZT界面与ZT反应形成钙钛矿相PZT,Pb~(2+)离子在PZT层中的扩散控制着合成PZT的反应
In the thesis, the synthesis, structure and properties of Pb(Zr_xTi_(1-x))O_3 (PZT) and Bi_(4-x)La_xTi_3O_(12) (BLT) and the synthesis strategies and growth mechanisms of 1 dimensional nanostructure were reviewed in detail, especially, the development on the researching of the 1 dimensional nanostructure of ferroelectric perovskite oxides such as BaTiO_3 and PZT was discussed. Combining the advantages of partial oxalate solid state reaction method and coprecipitation method, the pure perovskite PZT powders were directly synthesized by a two-stages prcipitation route at low temperature that is a new method and developed in these work. Nanosized PbZr_(0.52)Ti_(0.48)O_3 (PZT) powder with well disperse was prepared by poly(vinyl alcohol) (PVA) assisted two-stages precipitation route. The PZT precursor cluster was separated alone well by PVA gel. The synthesis of nanosized Bi_(3.25)La_(0.75)Ti_3O_(12) (BLT) powder with Bi-layer perovskite structure was realized by coprecipitation method. And innovatedly, in this work, single-crystalline tetragonal perovskite PbZr_(0.52)Ti_(0.48)O_3 (PZT), which is a quarternary oxide, nanorods and nanowires as well as poly-crystalline perovskite PZT nanotubes were synthesized by PVA or poly(acrylic acid) (PAA) assisted in the hydrothermal reaction method.Differential thermal analysis (DTA) and thermal gravitative analysis (TG) were employed to analyze the thermal behavior of the PZT and BLT precursor and X-ray diffraction (XRD) was used to follow the evaluation of PZT and BLT phase with the calcinations temperature. The morphology of the powder obtained was observed by field emission scanning electron microscopy (FESEM). In order to evaluate the chemical composition and thermal stability, the composition of the PZT and BLT powders was measured with ICP and EDX.Despite of the formation of the main phase that is the perovskite PZT phase, minor PbO appears in the PZT powder synthesized by coprecipitation method. The minor PbO phase will evaporate at high temperature and makes the PZT powder calcined at high temperature lack of Pb and the PZT powder calcined at low temperature with poor thermal stability. By enhancing the combination of the Zr~(4+) and Ti~(4+) ions, the evaporation of PbO is effectively avoided in the two-stage precipitation route. Not only is the stoichiometric and homogeneous PZT powder synthesized but also the powder has high thermal stability.
It is revealed by studying on the activation energies of the precursor for the formation of PZT phase that the phase transformation from precursor to perovskite PZT follows a consecutive mechanism, which can described as:Amorphous Precursor Powder------>Pyrochlore------> Perovskite PZT,which is not only suitable for the coprecipitation method but also for the partial oxalate coprecipitation and the two-stage precipitation route.A model for phase formation of PZT by the two-stage precipitation method is proposed based on the existence of two interfaces (PbO-PZT and PZT-ZT) of reaction and diffusion of cations. The Pb2+ ion diffuses to the interface of PZT-ZT and reacts with ZT to form PZT phase, which controlled by the Pb2+ ion diffusion through the PZT layer. Because of the resolution of TiC>2 in PbO phase, the rhombohedral PZT phase is preferential formed for low calcinations temperatures.The powders synthesized by the three precipitation methods mentioned above does not have very clean surface or boundary in distinct particles, in which the particles combine to chain because of sintering and the agglomeration is very heavy. However, when the two-stage precipitation is assisted with PVA, the powder obtained not only has clean surface or boundary in distinct particles but also is of nanosized particle and narrow distribution. The effect of PVA and quantity of PVA on the particle morphology was studied.For the synthesis of pure BLT phase, the critic factor is the preparation of transparent precursor solution. It is revealed that the bismuth oxynitrate derived from bismuth nitrate hydrolysis are not favorable for the formation of BLT phase with Bi-layer perovskite structure. The bismuth nitrate hydrolysis can be avoided by using dense concentration nitric acid solution as solvent. A single phase of BLT powder can be synthesized by directly coprecipitating the transparent BLT precursor solution in ammonia solution under stirring and no pyrochlore Bia^O? phase was found. The particle size of the BLT powder synthesized by calcinations at 700°C for 2 h is not bigger than lOOnm and the interaction of particles is loose with good dispersion.The single crystalline tetragonal perovskite PZT nanorods and nanowires as well as poly-crystalline PZT nanotube were firstly synthesized by polymer assisted hydrothermal reaction method. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) were employed to characterize the 1 dimensional nanostructure synthesized. The effect of polymer on the synthesis of PZT
nanostructure was studied and for the growth of single crystalline tetragonal perovskite PZT nanorods and nanowire or of polycrystalline PZT nanotube a model was proposed, respectively.The straight molecular chain of PVA will stretch under strong basicity by alcoholysis. Because of the hydrogen band and molecular effect, the stretched molecular chain assembles to a column polymolecular chain. The PZT crystallites formed in the hydrothermal reaction initially are absorbed on the surface of the column polymolecular chain and grow to a polycrystalline PZT nanotube.The adsorption of polymer on the surface of PZT crystallite, which forms a thin film, will result in the surface energy decreased. Because the tetragonal perovskite PZT is of poor anisotropic structure, the growth cell may deposit on the facet with high surface energy, which can be named as growing facet. The deposition of growth cell will breaks the polymer films and will enhance the deferential of surface energy between the facets with films and the growing facet, resulting in the [001] orientation growth of single crystalline tetragonal perovskite PZT. Because of the adsorption of PVA or PAA on the PZT crystal surface by hydrogen band or by chemical band, respectively, the single crystalline PZT nanorods are synthesized by only introducing PVA and the single crystalline PZT nanowires are synthesized by introducing both PVA and PAA.It is a feasible route for the synthesis of the single crystalline oxides, which are of poor anisotropic crystal structure, nanowires by introducing the polymer surface modified agent in the thermal reaction system to adsorb on the crystal facet for enhancing the deferential between the facets. The innovative work carried out in our researching not only is important for the synthesis of tetragonal oxides nanosturcture but also facilitates the researches on the properties of relative oxides nanostructure.
采用差热和热失重分析(DTA和TG)对合成PZT和BLT粉体的前驱体粉体的热行为进行了分析,利用X射线衍射(XRD)探讨了PZT、BLT晶相演化与煅烧温度的关系,场发射扫描电子显微镜(FESEM)观察了合成粉体的形貌随煅烧温度的演化过程,电感耦合等离子体发射光谱(ICP)和电子探针X射线显微分析(EDX)对合成的PZT、BLT粉体的化学组成进行了分析,并结合TG分析了PZT粉体的热稳定性。
共沉淀合成PZT粉体的过程中,除形成主晶相钙钛矿PZT外,还形成少量的PbO相,导致高温煅烧的粉体Pb含量减少,偏离设计组成;低温煅烧的粉体,热稳定性较差。对共沉淀法改进后发展的两步沉淀法和部分草酸盐共沉淀法,强化了Zr~(4+)、Ti~(4+)离子的结合,形成特殊的前驱体粉体微观结构,避免了PbO的挥发,不仅实现了钙钛矿相PZT的直接合成,保持了很好的设计组成,而且所得到的粉体具有良好的热稳定性。
对不同方法制备的前驱体粉体形成PZT相的活化能研究显示,不论是共沉淀法,还是改进后的部分草酸盐共沉淀法或两步沉淀法合成钙钛矿相PZT的反应均遵循连续反应机制,即
Amorphous Precursor Powder→Pyrochlore→Perovskite PZT,反应物首先反应生成焦绿石相,然后再转化为钙钛矿相。
建立了两步沉淀法合成钙钛矿相PZT的模型。在PbO和ZT反应合成PZT相过程中,形成PbO-PZT和PZT-ZT两个界面,Pb~(2+)离子扩散到PZT-ZT界面与ZT反应形成钙钛矿相PZT,Pb~(2+)离子在PZT层中的扩散控制着合成PZT的反应
In the thesis, the synthesis, structure and properties of Pb(Zr_xTi_(1-x))O_3 (PZT) and Bi_(4-x)La_xTi_3O_(12) (BLT) and the synthesis strategies and growth mechanisms of 1 dimensional nanostructure were reviewed in detail, especially, the development on the researching of the 1 dimensional nanostructure of ferroelectric perovskite oxides such as BaTiO_3 and PZT was discussed. Combining the advantages of partial oxalate solid state reaction method and coprecipitation method, the pure perovskite PZT powders were directly synthesized by a two-stages prcipitation route at low temperature that is a new method and developed in these work. Nanosized PbZr_(0.52)Ti_(0.48)O_3 (PZT) powder with well disperse was prepared by poly(vinyl alcohol) (PVA) assisted two-stages precipitation route. The PZT precursor cluster was separated alone well by PVA gel. The synthesis of nanosized Bi_(3.25)La_(0.75)Ti_3O_(12) (BLT) powder with Bi-layer perovskite structure was realized by coprecipitation method. And innovatedly, in this work, single-crystalline tetragonal perovskite PbZr_(0.52)Ti_(0.48)O_3 (PZT), which is a quarternary oxide, nanorods and nanowires as well as poly-crystalline perovskite PZT nanotubes were synthesized by PVA or poly(acrylic acid) (PAA) assisted in the hydrothermal reaction method.Differential thermal analysis (DTA) and thermal gravitative analysis (TG) were employed to analyze the thermal behavior of the PZT and BLT precursor and X-ray diffraction (XRD) was used to follow the evaluation of PZT and BLT phase with the calcinations temperature. The morphology of the powder obtained was observed by field emission scanning electron microscopy (FESEM). In order to evaluate the chemical composition and thermal stability, the composition of the PZT and BLT powders was measured with ICP and EDX.Despite of the formation of the main phase that is the perovskite PZT phase, minor PbO appears in the PZT powder synthesized by coprecipitation method. The minor PbO phase will evaporate at high temperature and makes the PZT powder calcined at high temperature lack of Pb and the PZT powder calcined at low temperature with poor thermal stability. By enhancing the combination of the Zr~(4+) and Ti~(4+) ions, the evaporation of PbO is effectively avoided in the two-stage precipitation route. Not only is the stoichiometric and homogeneous PZT powder synthesized but also the powder has high thermal stability.
It is revealed by studying on the activation energies of the precursor for the formation of PZT phase that the phase transformation from precursor to perovskite PZT follows a consecutive mechanism, which can described as:Amorphous Precursor Powder------>Pyrochlore------> Perovskite PZT,which is not only suitable for the coprecipitation method but also for the partial oxalate coprecipitation and the two-stage precipitation route.A model for phase formation of PZT by the two-stage precipitation method is proposed based on the existence of two interfaces (PbO-PZT and PZT-ZT) of reaction and diffusion of cations. The Pb2+ ion diffuses to the interface of PZT-ZT and reacts with ZT to form PZT phase, which controlled by the Pb2+ ion diffusion through the PZT layer. Because of the resolution of TiC>2 in PbO phase, the rhombohedral PZT phase is preferential formed for low calcinations temperatures.The powders synthesized by the three precipitation methods mentioned above does not have very clean surface or boundary in distinct particles, in which the particles combine to chain because of sintering and the agglomeration is very heavy. However, when the two-stage precipitation is assisted with PVA, the powder obtained not only has clean surface or boundary in distinct particles but also is of nanosized particle and narrow distribution. The effect of PVA and quantity of PVA on the particle morphology was studied.For the synthesis of pure BLT phase, the critic factor is the preparation of transparent precursor solution. It is revealed that the bismuth oxynitrate derived from bismuth nitrate hydrolysis are not favorable for the formation of BLT phase with Bi-layer perovskite structure. The bismuth nitrate hydrolysis can be avoided by using dense concentration nitric acid solution as solvent. A single phase of BLT powder can be synthesized by directly coprecipitating the transparent BLT precursor solution in ammonia solution under stirring and no pyrochlore Bia^O? phase was found. The particle size of the BLT powder synthesized by calcinations at 700°C for 2 h is not bigger than lOOnm and the interaction of particles is loose with good dispersion.The single crystalline tetragonal perovskite PZT nanorods and nanowires as well as poly-crystalline PZT nanotube were firstly synthesized by polymer assisted hydrothermal reaction method. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) were employed to characterize the 1 dimensional nanostructure synthesized. The effect of polymer on the synthesis of PZT
nanostructure was studied and for the growth of single crystalline tetragonal perovskite PZT nanorods and nanowire or of polycrystalline PZT nanotube a model was proposed, respectively.The straight molecular chain of PVA will stretch under strong basicity by alcoholysis. Because of the hydrogen band and molecular effect, the stretched molecular chain assembles to a column polymolecular chain. The PZT crystallites formed in the hydrothermal reaction initially are absorbed on the surface of the column polymolecular chain and grow to a polycrystalline PZT nanotube.The adsorption of polymer on the surface of PZT crystallite, which forms a thin film, will result in the surface energy decreased. Because the tetragonal perovskite PZT is of poor anisotropic structure, the growth cell may deposit on the facet with high surface energy, which can be named as growing facet. The deposition of growth cell will breaks the polymer films and will enhance the deferential of surface energy between the facets with films and the growing facet, resulting in the [001] orientation growth of single crystalline tetragonal perovskite PZT. Because of the adsorption of PVA or PAA on the PZT crystal surface by hydrogen band or by chemical band, respectively, the single crystalline PZT nanorods are synthesized by only introducing PVA and the single crystalline PZT nanowires are synthesized by introducing both PVA and PAA.It is a feasible route for the synthesis of the single crystalline oxides, which are of poor anisotropic crystal structure, nanowires by introducing the polymer surface modified agent in the thermal reaction system to adsorb on the crystal facet for enhancing the deferential between the facets. The innovative work carried out in our researching not only is important for the synthesis of tetragonal oxides nanosturcture but also facilitates the researches on the properties of relative oxides nanostructure.
引文
[1] Dragan Damjanovic, Rep. Prog. Phys. 61(1998)1267-1324;
[2] B. Noheda, Current Opinion in Solid State and Materials Science, 6(2002)27-34;
[3] 晏海学,李承恩,周家光,朱为民,无机非金属材料学报,15(2000)2:209-220
[4] K. Kakegawa, K. Arai, Y. Sasaki and T. Tomizawa, J. Am. Ceram. Soc.,71 (1)(1988)c-49-c-52;
[5] T. Yarnamoto, Am. Cerarn. Soc. Bull., 71(6)(1992)978-85;
[6] C.D.E. Lakeman and D.A. Payne, J. Am. Ceram. Soc., 75(11) (1992)3091-96;
[7] A. Wu, I.M, Miranda Salvako, P.M. Vilarinho and J.L. Baptista, J. Am. Ceram. Sot., 81 (10)(1998)2640-44
[8] B.A. Menegazzo, J.A. Etras, J. Am. Ceram. Sot., 76(11)(1993)2734;
[9] B. Guiffard and M Troccaz, Mater. Res. Bull., 33 (1998)1759-1768;
[10] B.H. Park, B.S. Kang, S.D. Bu, T.W. Nob, J. Lee and W. Jo, Nature, 401(14)(1999)682-684;
[11] U. Chon, H.M. Jang, I.-W. Park, Solid State Communications 127(2003)469-473;
[12] 沈志坚,方中华,李廷凯,丁子上,硅酸盐学报,19(1991)5:403-408;
[13] 徐刚,马峻峰,沈志坚,丁子上,硅酸盐通报,(1999)5:7一10;
[14] Y. Li, W. Weng, K. Cheng, P. Du, G. Shen, J. Wang, G. Han, J. Mater. Sci. Lett. 22(2003)1015-1016;
[15] J.J. Urban, J.E. Spanier, L. Ouyang, W.S. Yun, H. Park, Adv. Mater. 15(2003)423
[16] S.J. Limmer, S. Seraji, M.J. Forbess, Y. Wu, T.P. Chou, C. Nguyen, G.Z. Cao, Adv. Mater. 13(2001)1269;
[17] 姚建曦,CdS/有机物纳米复合材料的制备及其发光性能的研究,浙江大学博士学位论文,2003年:
[18] R.N. Das, A. Pathak, S.K. Saka, S. Sannigrahi, P. Pramanik, Mater. Res. Bull. 36(2001)1539-1549;
[19] T.K. Mandal, S. Ram, Mater. Lett. 57(2003(2432-2442;
[20] D. Xie., W. Pan, Mater. Lett., 57(2003)2970-2974;
[21] S-B. Cho, M. Oledzka, R.E. Riman, J. Cryst. Grow. 226(2001)313-326.
[2] B. Noheda, Current Opinion in Solid State and Materials Science, 6(2002)27-34;
[3] 晏海学,李承恩,周家光,朱为民,无机非金属材料学报,15(2000)2:209-220
[4] K. Kakegawa, K. Arai, Y. Sasaki and T. Tomizawa, J. Am. Ceram. Soc.,71 (1)(1988)c-49-c-52;
[5] T. Yarnamoto, Am. Cerarn. Soc. Bull., 71(6)(1992)978-85;
[6] C.D.E. Lakeman and D.A. Payne, J. Am. Ceram. Soc., 75(11) (1992)3091-96;
[7] A. Wu, I.M, Miranda Salvako, P.M. Vilarinho and J.L. Baptista, J. Am. Ceram. Sot., 81 (10)(1998)2640-44
[8] B.A. Menegazzo, J.A. Etras, J. Am. Ceram. Sot., 76(11)(1993)2734;
[9] B. Guiffard and M Troccaz, Mater. Res. Bull., 33 (1998)1759-1768;
[10] B.H. Park, B.S. Kang, S.D. Bu, T.W. Nob, J. Lee and W. Jo, Nature, 401(14)(1999)682-684;
[11] U. Chon, H.M. Jang, I.-W. Park, Solid State Communications 127(2003)469-473;
[12] 沈志坚,方中华,李廷凯,丁子上,硅酸盐学报,19(1991)5:403-408;
[13] 徐刚,马峻峰,沈志坚,丁子上,硅酸盐通报,(1999)5:7一10;
[14] Y. Li, W. Weng, K. Cheng, P. Du, G. Shen, J. Wang, G. Han, J. Mater. Sci. Lett. 22(2003)1015-1016;
[15] J.J. Urban, J.E. Spanier, L. Ouyang, W.S. Yun, H. Park, Adv. Mater. 15(2003)423
[16] S.J. Limmer, S. Seraji, M.J. Forbess, Y. Wu, T.P. Chou, C. Nguyen, G.Z. Cao, Adv. Mater. 13(2001)1269;
[17] 姚建曦,CdS/有机物纳米复合材料的制备及其发光性能的研究,浙江大学博士学位论文,2003年:
[18] R.N. Das, A. Pathak, S.K. Saka, S. Sannigrahi, P. Pramanik, Mater. Res. Bull. 36(2001)1539-1549;
[19] T.K. Mandal, S. Ram, Mater. Lett. 57(2003(2432-2442;
[20] D. Xie., W. Pan, Mater. Lett., 57(2003)2970-2974;
[21] S-B. Cho, M. Oledzka, R.E. Riman, J. Cryst. Grow. 226(2001)313-326.