烧结温度对0.55Pb(Ni1/3Nb2/3)O3-0.45Pb(Zr0.3Ti0.7)O3压电陶瓷性能的影响

0.55Pb(Ni1/3Nb2/3)3-0.45Pb(Zr0.3Ti0.7)O3(0.55PNN-0.45PZT)组分的弛豫型压电陶瓷因具有较高的压电性能,已被作为制备含金属芯压电陶瓷纤维的材料等使用。为了进一步提高压电陶瓷纤维的电学性能,采用传统固相烧结法制备了0.55PNN-0.45PZT压电陶瓷,研究了烧结温度对材料结构、表面形貌和电学性能的影响。结果表明,在烧结温度为1200℃时,材料的各方面性能较佳:密度为8.12g/cm3,d33=850pC/N,kp=0.62,εr=7317,tanδ=0.033,Qm=41.66。     

不同镁源反应物对反应烧结制备Pb（Mg1/3Nb2/3）O3陶瓷的影响

采用MgO和(MgCO3)4·Mg(OH)2·5H2O为不同镁源反应物,通过高温反应烧结工艺制备Pb(Mg1/3Nb2/3)O0.(PMN)陶瓷,研究不同Mg源反应物对PMN陶瓷物相组成、相对密度及组织形貌的影响.结果表明:以MgO为前驱体时.由于其反应活性差,扩散和反应不均匀,导致烧结样品中有焦绿石相残留,且焦绿石相对晶界的钉扎阻碍作用使得致密化过程进行相对较慢,所得PMN样品致密度相对较低;而以(MgCO3)4·Mg(OH)2·5H2O为前驱体时,因其受热分解可以得到大比表面积、高反应活性的MgO,从而可以制得高致密度且具有单一钙钛矿相组成的PMN陶瓷材料.     

Ba（Zn1/3Nb2/3）O3陶瓷A位K^＋取代对烧结温度的影响

在Ba（Zn1/3Nb2/3）O3微波介质陶瓷的A位用K^＋取代Ba^2＋形成固溶体，研究其对于系统烧结温度的影响。研究表明A位K^＋的引入有效改善了系统的烧结特性，使烧结温度下降到1300℃以下。这是由于系统中产生了氧空位造成的，空位的生成增加了系统中的缺陷，促进了离子的相互扩散，从而降低了系统的烧结温度。     

TiO_2/Al烧结反应生成的Al_2O_3/Ti_xAl_y复合材料研究

采用挤压铸造法,先制备 TiO_2/Al 坯块,经随后高温烧结反应,可生成 Al_2O_3/Ti_xAl_y 复合材料。DTA 分析表明 TiO_2粉末与纯 Al 之间的反应具有放热特征。X 射线衍射分析与透射电镜观察发现反应产物主要为α-Al_2O_3与 Ti_xAl_y。反应过程中 TiO_2粉末首先被熔融态 Al 还原成α-Al_2O_3与 Ti,而后 Ti与 Al 通过扩散反应形成多种 Ti_xAl_y 金属间化合物。     

三元陶瓷Pb(In1/2Nb1/2)O3-Pb(Ni1/3Nb2/3)O3-PbTiO3准同型相界附近组分的介电、铁电和压电性能

铅基复合钙钛矿铁电材料广泛应用于机电传感器、致动器和换能器。二元铁电固溶体Pb(Ni_1/3Nb_2/3)O₃- PbTiO₃(PNN-PT)由于其在准同型相界(MPB)区域具有优异的压电、介电性能而备受关注。然而较大的介电损耗和较低的居里温度限制了其在高温高功率器件方面的应用。本研究通过引入Pb(In_1/2Nb_1/2)O₃ (PIN)作为第三组元改善PNN-PT的电学性能, 提高其居里温度; 通过两步法合成了MPB区域的三元铁电陶瓷Pb(In_1/2Nb_1/2)O₃- Pb(Ni_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PNN-PT), 研究了其结构、介电、铁电和压电性能。制备的所有组分陶瓷具有纯的钙钛矿结构。随着PT含量的增加, 陶瓷结构从三方相转变为四方相。通过XRD分析得到了室温下PIN-PNN-PT体系的MPB相图。体系的居里温度由于PIN的加入得到了很大的提高, 更重要的是PIN的引入降低了PNN-PT体系的介电损耗和电导。MPB处的组分展现出了优异的电学性能, 室温下, 性能最优组分为0.30PIN-0.33PNN-0.37PT: d₃₃=417 pC/N, T_C=200 ℃, ε′= 3206, tanδ=0.033, P_r=33.5 μC/cm², E_C=14.1 kV/cm。引入PNN-PT的PIN第三组元使得体系的居里温度和压电性得到提高的同时降低了的介电损耗和电导率, 因此, PIN-PNN-PT三元铁电陶瓷在高温高功率换能器等方面具备一定的应用潜力。     

添加剂MnCO3和BaZrO3对Ba(Zn1/3Nb2/3)O3陶瓷烧结温度和介电性能的影响

采用传统的固相烧结法制备Ba(Zn_(1/3) Nb_(2/3))O_3(BZN)和(1-x)Ba(Zn_(1/3)Nb_(2/3))O_3-xSr(Zn_(1/3)Nb_(2/3))O_3(BSZN)陶瓷,研究MnCO_3和BaZrO_3添加剂对其烧结温度和介电性能的影响。研究表明二者均是很好的助熔剂,在烧结过程中形成液相促进原子扩散从而降低烧结温度,本研究中的最佳烧结温度为1260℃(5#样品)。MnCO_3和BaZrO_3对于改善系统的介电性能均有较好的效果,合理调整添加剂的用量可以有效的改善介电性能。0.35BZN-0.65SZN-1%MnCO_3样品的介电性能最佳且烧结温度低于1300℃。     

Ti(C,N)基金属陶瓷的烧结工艺研究

采用真空烧结工艺制备了Ti(C,N)基金属陶瓷,研究了烧结温度和保温时间对Ti(C,N)基金属陶瓷显微组织和力学性能的影响,并用SEM观察其断口形貌.结果表明:随着烧结温度的升高,金属陶瓷的组织逐渐变得均匀,硬质颗粒逐渐球化,且其环形相逐渐变得完整;温度过高,保温时间过长,晶粒都会明显长大,环形相变厚,导致材料性能下降.经1440℃烧结,保温60min,可获得较佳的性能,其抗弯强度达1914.2MPa,硬度HRA达90.1.     

(1-x)Ca0.61 La0.26 TiO3-xLa(Mg0.5 Ti0.5)O3陶瓷的微波烧结及微波介电性能研究

采用微波烧结制备(1-x)Ca0.61La0.26TiO3-xLa(Mg0.5Ti0.5)O3[x=0.35～0.60,(1-x)CLT-xLMT]微波介质陶瓷,研究烧结工艺和成分配比对其物相组成、显微结构和微波介电性能的影响.结果表明,与常规烧结相比,(1-x)CLT-xLMT陶瓷的微波烧结温度低100℃,烧结时间缩...     

Pb(Zn1/3Nb2/3)O3-Ba(Zn1/3Nb2/3)O3铁电陶瓷结构与性能的研究

采用固相反应的方法系统地研究了BZN稳定PZN基陶瓷的相结构与介电性能.随着BZN含量的增加,PZN-BZN陶瓷中钙钛矿相的稳定性增强,居里温度近似呈线性下降,室温介电常数和介质损耗随也显著降低,最小值分别为380和0.002.为获得100%钙钛矿结构的PZN基陶瓷所需BZN的最小用量为8mol%～10mol%,当BZN的mol%超过15mol%时,PZN基陶瓷中钙钛矿相所占的百分比不再受烧结工艺的影响,基本保持100%.1kHz时Pb0.9Ba0.1Zn1/3Nb2/3O3陶瓷的最大介电常数Kmax=8680,tgδ=0.02,相应的居里温度Tm为24℃.     

Preparation of Pb(Mg1/3Nb2/3)O3–Pb(Zn1/3Nb2/3)O3 ceramics by the B-site precursor method and dielectric characteristics

Powders in the Pb(Mg1/3Nb2/3)O3–Pb(Zn1/3Nb2/3)O3 system, with a high perovskite yield, were prepared by a B-site precursor method. PbO was added to pre-reacted B-site components of Mg1-xZnxNb2O6 solid solution, which was further calcined to form a perovskite structure. Perovskite phase contents and lattice parameters were obtained from X-ray analyses. Weak-field low-frequency dielectric constants and losses of sintered pellets were measured as functions of composition, temperature and frequency. Dielectric relaxation behaviours were investigated in terms of diffuseness coefficients. Microstructures were observed to correlate with other characteristics. © 1998 Chapman & Hall     

Synthesis of Pb(Mg1/3Nb2/3) O3 perovskite by an alkoxide method

Pb(Mg_1/3Nb_2/3)O₃ materials have been synthesized using sol-gel, freeze-drying or spray-pyrolysis techniques. The as-prepared powders were of an amorphous form which could be converted into a crystalline form by calcination. The pyrochlore phase was inevitably formed with an accompanying perovskite phase. As the calcining temperature increased, greater proportions of the desired perovskite phase occurred. The residual pyrochlore phase could be completely transformed into the perovskite phase when the powders were prepared via freeze-drying or by a spray-pyrolysis method. The maximum proportion of the pyrochlore phase was, however, only 92% when the powders were synthesized by a sol-gel route. Thermal gravimetric analysis/differential thermal analysis (TGA/DTA) and infrared transmission spectroscopy (FTIR) indicated that Mg(OEt)₂ and Nb(OEt)₅ formed a double alkoxide but Pb(OAc)₂ formed separate clusters during the hydrolysis of the solution in the sol-gel process. Inhomogeneous mixing meant that the intermediate phase formed was rather difficult to eliminate completely. Homogeneous mixing was preserved when the solution was directly freeze dried or spray pyrolysed. The size of the preferentially formed pyrochlore phase was very fine and further transformation was feasible. Pb(Mg_1/3Nb_2/3)O₃ materials, free of the pyrochlore phase, could therefore be obtained.     

液相包裹法制备Pb(Mg1/3Nb2/3)O3-CoFe2O4磁电耦合材料

以无机盐Nb2O5、Mg(NO3)2、Pb(NO3)4、Co(NO3)2、Fe2(NO3)3为原料,柠檬酸和EDTA为络合剂,分别制备了Nb5+、Mg2+、Pb2+、Co2+、Fe3+等离子的络合溶液。采用络合法制备了铌酸镁-铁酸钴先驱体(MgNb2O6-CoFe2O4,简称MN-CFO)。此先驱体在1000℃煅烧1h后,得到纯净的MgNb2O6-CoFe2O4固溶体。采用液相包裹法制备了铌镁酸铅-铁酸钴(Pb(Mg1/3Nb2/3)O3-CoFe2O4)先驱体,在1000℃煅烧1h,Pb(Mg1/3Nb2/3)O3-CoFe2O4先驱体分解为具有铁电相Pb(Mg1/3Nb2/3)O3和铁磁相CoFe2O4的复相组织。研究了10%过量的PbO对煅烧过程中烧绿石相向铁电相的转变作用,并在700℃煅烧5h条件下制备了不含烧绿石相的Pb(Mg1/3Nb2/3)O3-CoFe2O4固溶体。     

Dielectric properties of low-fitting Pb(Mg1/3Nb2/3)1−xTixO3-Bi2O3/Li2O ceramics

Dielectric properties of low-firing Pb(Mg_1/3Nb_2/3)_1–x Ti _x O₃-Bi₂O₃/Li₂O ceramics are studied in this work. With the addition of Bi₂O₃/Li₂O eutectic composition, the sintering temperature of PMN_1–x PT _x could be lowered to 900° C. Relaxor behaviour of PMN_1–x PT _x is enhanced by the incorporation of Bi₂O₃/Li₂O due to the substitution of Bi⁺³/Li⁺ into the PMN_1–x PT _x framework. Bi₂O₃/Li₂O eutectic composition is used as a fluxing agent, Curie shifter and depressor. Evaporation of Bi₂O₃/Li₂O and PbO during firing is checked and examined via energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) is used to clarify the Curie shifting and depressing effect of Bi₂O₃/Li₂O.     

Fabrication of Monolithic Ti3SiC2 Ceramic Through Reactive Sintering of Ti/Si/2TiC

Fabrication of monolithic Ti₃SiC₂ has been investigated through the route of reactive sintering of Ti/Si/2TiC mixtures. Significant phase differences existed between the surface and the interior of as-synthesized products due to the evaporation of Si during the reaction process. The use of a 3Ti/SiC/C mixture as a powder bed could control the evaporation of Si and develop monolithic Ti₃SiC₂. A reaction model for the formation of Ti₃SiC₂ in the Ti/Si/2TiC system is discussed.On leave from