| With the rapid development of modern science and technology, multifunctional materials with high integration have been the hot topic. Lead/bismuth-based perovskite-type oxides have been attracting extensive attention because of their wide variety of physical properties (ferroelectric and ferromagnetic, etc.). Some of them exhibit excellent piezoelectric properties and high Curie temperature (TC) in the morphotropic phase boundary (MPB), making them an important class of functional materials. In addition to its ferroelectricity, lead titanate (PbTiO3) compounds exhibit unique negative thermal expansion (NTE), which provides the possibility to control the coefficient of thermal expansion of materials, ensuring them work under higher temperature conditions. In this paper, the properties of traditional piezoelectric materials have been successfully modified by chemical substitutions. In addition, new high-performance piezoelectric materials were also explored in both lead and lead-free based systems. Furthermore, the thermal expansion properties of the PbTiO3-based compounds were studied, and unique large volume shrinkages and multifunctional zero thermal expansion (ZTE) materials were obtained. The crystal structure, thermal expansion and related electrical properties of the materials were systematically studied, and the related mechanisms were also discussed.Lead-based piezoelectric materis of Pb(Zro 54Tio.46)03-KNbO3 and PbTiO3-Bi(Ni1/2Hf1/2)O3, and lead-free systems of Bi0.5Na0.5TiO3-Ba(Ni1/3Nb2/3)O3, K0.5Na0.5NbO3:ZnO and Bi(Zn0.5Ti0.5)O3-BiFe03 were investigated. The disadvantages of the traditional piezoelectric materials of Pb(Zr0.54Ti0.46)O3, Bi0.5Na0.5TiO3, and K0.5Na0.5NbO33 have been greatly improved by chemical modifications. For example, the piezoelectric coefficient d33 of Pb(Zr0.54Ti0.46)O3 has been improved significantly without reducing the TC; The coercive field of Bi0.5Na0.5TiO3 has been much reduced, resulting in the improved piezoelectric coefficient d33. The sinterability of K0.5Na0.5NbO3 were improved, and its temperature stability of property has also been enhanced. Meanwhile, the exploration of new piezoelectric materials has also achieved good results. High d33 was obtained at the MPB of PbTiO3-Bi(Ni1/2Hf1/2)O3, which is comparable to that of the well-known 0.64PbTiO3-0.36BiScO3 (d33=460 pC/N). In the Bi(Zn0.5Ti0.4)03-BiFe03 system, the MPB which the tetragonal and monoclinic phases coexist, and the single monoclinic phase are observed. In particular, the system exhibits giant polarization, suggesting it a potential high-performance lead-free piezoelectric materials.In the present PbTiO3-based ferroelectrics, most of them show the weakened NTE compared to PbTiO3. Up to now, only the PbTiO3-BiFeO3 and (Pb,Cd)TiO3 exhibit abnormal enhanced tetragonality (c/a) and NTE. In this paper, solid solutions between PbTiO3 and high polarity compounds of Bi(Zn0.5Ti0.5)O3, BiCoO3, and PbVO3 were prepared by high-temperature and high-pressure method. The crystal structure of all investugated systems has been changed abnormally, leading to the unusually enhanced c/a and TC. Intriguingly, large volume shrinkages were observed in the PbTiO3-BiCoO3 and PbTiO3-PbVO3 systems. Especially, a large volume shrinkage as high as 4.8% has been observed in PbTiO3-BiCoO3 system. The unique phenomenon could be attibuted to the multiple couplings of ferroelectricity-lattice and spin-lattice by means of synchrotron radiation, neutron powder diffraction, X-ray absorption fine structure, and first-principles calculations.The multifunctionalization of ZTE materials was successfully achieved in the PbTi03-Bi(Co0.5Ti0.5)O3 system. The ZTE semiconductor ferroelectric material was obtained at the non-stoichiometric 0.6PbTiO3-0.4Bi(Co0.55Ti0.45)O3-? by substituting Ti with a small amount of Co at 0.6PbTiO3-0.4Bi(Co0.5Ti0.5)O3. The present study provides an effective way to explore multifunctional ZTE materials. |
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