Effect of annealing time on morphological characteristics of Ba(Zr,Ti)O-3 thin films

Ba(Zr0.50Ti0.50)O-3 thin films were prepared by the polymeric precursor method using the annealing low temperature of 300 degrees C for 8, 16, 24, 48, 96 and 192 It in a furnace tube with oxygen atmosphere. The X-ray diffraction patterns revealed that the film annealed for 192 h presented some crystallographic planes (1 0 0), (1 1 0) and (2 0 0) in its crystalline lattice. Fourier transformed infrared presented the formation of metal-oxygen stretching at around 756 cm(-1). The atomic force microscopy analysis presented the growth of granules in the Ba(Zr0.50Ti0.50)O-3 films annealed from 8 to 96 h. The crystalline film annealed for 192 h already presents grains in its perovskite structure. It evidenced a reduction in the thickness of the thin films with the increase of the annealing time. (C) 2006 Elsevier B.V. All rights reserved.

Infrared studies of the monoclinic-tetragonal phase transition in Pb(Zr, Ti)O-3 ceramics

Recently, the observation of a new monoclinic phase in the PbZr1-xTixO3 (PZT) system in the vicinity of the morphotropic phase boundary was reported. Investigations of this new phase were reported using different techniques such as high-resolution synchrotron x-ray powder diffraction and Raman spectroscopy. In this work, the monoclinic --> tetragonal phase transition in PbZr0.50Ti0.50O3 ceramics was studied using infrared spectroscopy between 1000 and 400 cm(-1). The four possible nu(1)-stretching modes (Ti-O and Zr-O stretch) in the BO6 octahedron in the ABO(3) structure of PZT in this region were monitored as a function of temperature. The lower-frequency mode nu(1)-(Zr-O) remains practically unaltered, while both intermediate nu(1)-(Ti-O) modes decrease linearly as temperature increases from 89 to 263 K. In contrast, the higher-frequency nu(1)-(Ti-O) and nu(1)-(Zr-O) modes present anomalous behaviour around 178 K. The singularity observed at this mode was associated with the monoclinic --> tetragonal phase transition in PbZr0.50Ti0.50O3 ceramics.

Phase transition and dielectric properties of La-doped Pb(Zr, Ti)O-3 antiferroelectric ceramics

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Study of structural evolution and photoluminescent properties at room temperature of Ca(Zr, Ti)O-3 powders

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Improvement of the dielectric and ferroelectric properties in superlattice structure of Pb(Zr,Ti)O-3 thin films grown by a chemical solution route

Making heterolayered perovskite materials constitutes an approach for the creation of better dielectric and ferroelectric properties. In the experiment reported here, heterolayered PZT40/PZT60 films were grown on Pt/Ti/SiO2/Si (100) by a chemical solution deposition. The dielectric constant of the heterolayered thin film was significantly enhanced compared with that of pure PZT40 and PZT60 thin films. A dielectric constant of 701 at 100 kHz was observed for a stacking periodicity of six layers having a total thickness of 150 nm. The heterolayered film exhibited greater remanent polarization than PZT60 and PZT40 films. The values of remanent polarization were 7.9, 18.5, and 31 muC/cm(2), respectively, for pure PZT60, PZT40, and heterolayered thin films, suggesting that the superior dielectric and ferroelectric properties of the heterolayered thin film resulted from a cooperative interaction between the ferroelectric phases made from alternating tetragonal and rhombohedral phases of PZT, simulating the morphotropic phase boundary of this system. (C) 2004 American Institute of Physics.

Preparation of Pb(Zr,Ti)O-3 thin films by soft chemical route

Lead zirconate titanate, Pb(Zr0.3Ti0.7)O-3 (PZT) thin films were prepared with success by the polymeric precursor method. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), Micro-Raman spectroscopy and X-ray diffraction (XRD) were used to investigate the formation of the PZT perovskite phase. X-ray diffraction revealed that the film showed good crystallinity and no presence of secondary phases was identified. This indicates that the PZT thin films were crystallized in a single phase. PZT thin films showed a well-developed dense grain structure with uniform distribution, without the presence of rosette structure. The Raman spectra undoubtedly revealed these thin films in the tetragonal phase. For the thin films annealed at the 500-700 degreesC range, the vibration modes of the oxygen sublattice of the PZT perovskite phase were confirmed by FT-IR. The room temperature dielectric constant and dielectric loss of the PZT films, measured at 1 kHz were 646 and 0.090, respectively, for thin film with 365 nm thickness annealed at 700 degreesC for 2 h. A typical P-E hysteresis loop was observed and the measured values of P-s, P-r and E-c were 68 muC/cm(2), 44 muC/cm(2) and 123 kV/cm, respectively. The leakage current density was about 4.8 x 10(-7) A/cm(2) at 1.5 V. (C) 2003 Elsevier Ltd. All rights reserved.

Structure and optical properties of [Ba(1-x)Y(2x/3)](Zr(0.25)Ti(0.75))O(3) powders

[Ba(1-x)Y(2x/3)](Zr(0.25)Ti(0.75))O(3) powders with different yttrium concentrations (x = 0, 0.025 and 0.05) were prepared by solid state reaction. These powders were analyzed by X-ray diffraction (XRD). Fourier transform Raman scattering (FT-RS), Fourier transform infrared (FT-IR) and X-ray absorption near-edge (XANES) spectroscopies. The optical properties were investigated by means of ultraviolet-visible (UV-vis) absorption spectroscopy and photoluminescence (PL) measurements. Even with the addition of yttrium, the XRD patterns revealed that all powders crystallize in a perovskite-type cubic structure. FT-RS and FT-IR spectra indicated that the presence of [YO(6)] clusters is able to change the interaction forces between the O-Ti-O and O-Zr-O bonds. XANES spectra were used to obtain information on the off-center Ti displacements or distortion effects on the [TiO(6)] clusters. The different optical band gap values estimated from UV-vis spectra suggested the existence of intermediary energy levels (shallow or deep holes) within the band gap. The PL measurements carried out with a 350 nm wavelength at room temperature showed that all powders present typical broad band emissions in the blue region. (C) 2010 Elsevier Masson SAS. All rights reserved.

LnMsbO_6和Ln_2M_2O_7 (M = Zr, Ti)复合氧化物的合成、组成、结构及发光等性质的研究

在综合文献报导的基础上，我们选择了LnMsbO_6和Ln_2M_2O_7 (M = Zr, Ti)做为研究体系，对其合成、组成、结构以及稀土离子在其中的发光性质进行了较为系统的研究。用氢氧化物共沉淀的方法，在等摩尔阳离子原料配比条件下，我们制备了LnMsbO_6和Ln_2M_2O_7(M = Zr, Ti, Ln = La - Yb, Y除Ce和Pm)。根据对组成的分析结果并与文献对比，我们认为得到的化合物组成与给出的分子式是一致的。由热分析并结合x-ray衍射分析对LnZrsbO_6的形成反应进行了研究，其结果表明化合物的形成过程是一个较慢的固相反应过程。通过x-ray粉沫衍射物相分析并结合掺杂Eu~(3+)的发光光谱，我们确定了在不同条件下合成的LnMsbO_6和Ln_2M_2O_7化合物的结构类型，并计算了所有化合物的晶胞参数。在对上述结构特性及其变化规律进行研究后，我们认为Ln_2M_2O_7结构变化规律与ΔZ/(d~2) (Z为阳离子电荷，d为阳离子与阴离距离)有关，随ΔZ/(d~2)值由小到大，Ln_2M_2O_7(M = Zr, Ti)先是形成具有荧石结构的阳离子无序固溶体，然后逐渐过渡到荧石结构的变型——有序的立方烧绿石结构，最后变型到单斜晶系结构。LnMsbO_6(M = Zr, Ti)低温相结构与Ln_2M_2O_7(M = Zr, Ti)是有联系的，即基本保持了其立方晶系结构。然后锑的加入使这种结构变得很不稳定，因此在高温灼烧下上述立方相将不可逆地变为更稳定的高温结构相。利用磁天平对LnMsbO_6和Ln_2M_2O_7进行了室温条件下的磁学性质测量，其玻尔磁子数的实验值与Van Vleck理论值符合较好。由此也可说以说明化合物的组成与给出的分子式是一致的。用荧光光谱仪对Eu~(3+)在不同基质中做发光光谱，其结果表明Eu~(3+)在烧绿石结构的Ln_2M_2O_7中，Ln~(3+)是处于具有反演中心的D_(3d)格位，这时~5D_0 → ~7F_2的电体极跃迁（～610nm）是被禁阻的，因此Eu~(3+)主要的发光为~5D_0 → ~7F_1磁体极跃迁（～590nm），并劈裂为两条谱线。在其它不具有反演中心的格位中Eu~(3+)的~5D_0 → ~7F_2跃迁则是较强的。在La~(3+)有着多个较低对称性格位的La_2Ti_2O_7:Eu中，无论是Eu~(3+)的激发光谱，还是发射光谱，其~5D_0与~7F_0之间的跃迁谱线都不只一条，这与La~(3+)多对称性格位特性是一致的。在立方荧石结构的LnZrsbO_6:Eu中，用Eu~(3+)电荷迁移带激发的发光光谱与用其它激发带激发的很不相同，其~5D_1能级的跃迁谱线非常强，我们认为这可能是由于电荷迁移激发态，将大部分能量传递给3~5D_1能级的结果。另外，我们比较了在Ln_2Zr_2O_7和LnZrsbO_6中Eu~(3+)的发光强度，发现前者要比后者强许多。在研究Bi~(3+)对Eu~(3+)的敏化作用时，我们发现在Y_2M_2O_7:Bi, Bu中Bi~(3+)对Eu~(3+)有较好的敏化作用，而在YMsbO_6:Bi, Eu中则没有。同时我们注意到对于Eu~(3+)取代六配位La~(3+)格位时，其电荷还移带位置和符合Hoefdraad认为是不变的规律，而是随着基质晶格的不同发生变化的。对Dy~(3+)在LnMsbO_6和Ln_2M_2O_7基质中发光性质研究中，我们看到Dy~(3+)的发光主要为兰色的~4F_(9/2) → ~6H_(15/2)跃迁(～480nm)和黄色的~4F_(9/2) → ~6H_(13/2)跃迁(～580nm)。其黄光与兰光的强度比值（R）随基质晶格的不同可以有很大的变化。一般情况下R值总是要大小1，且不随湿度和Dy~(3+)掺杂浓度变化。同时我们比较了在Ln_2Zr_2O_7和LnZrsbO_6 (Ln = Y, Gd, La)基质体系中Dy~(3+)的发光强度，发现同Eu~(3+)类似前者较后者强许多。在论文中我们给出了在Y_2M_2O_7和YMsbO_6 (M = Zr, Ti)中Sm~(3+)的激发光谱与发射光谱，从中可以看到当Sm~(3+)在Y_2Ti_2O_7中取代占据D_(3d)格位的Y~(3+)时，其~4G_(5/2) → ~6H_(9/2) (～650nm)电体极跃迁是被禁阻的。同时还给出了在YZrsbO_6中H_0~(3+)和Er~(3+)的激发光谱与发射光谱。此外，我们研究了Eu~(3+)和Dy~(3+)在一些基质体系中发光强度随温度的变化规律。发现Y_2Zr_2O_7:Eu的临界猝来温度要比La_2Zr_2O_7:Eu的高，Ln_2Zr_2O_7:Dy (Ln = La, Y)的温度猝来曲线则大致相同，且随温度和猝来要比Ln_2Zr_2O_7:Eu缓慢，对于上述现象我们利用位形坐标给出了一定的解释。然而所有的样品发光强度从室温开始，随温度的升高都是单调下降的。

Structure and optical properties of [Ba1-xY2x/3](Zr0.25Ti0.75)O-3 powders

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Relaxor ferroelectricity and electric-field-driven structural transformation in the giant lead-free piezoelectric (Ba,Ca)(Ti, Zr)O-3

There is great interest in lead-free (Ba0.85Ca0.15)(Ti0.90Zr0.10)O-3 (15/10BCTZ) because of its exceptionally large piezoelectric response Liu and Ren, Phys. Rev. Lett. 103, 257602 (2009)]. In this paper, we have analyzed the nature of: (i) crystallographic phase coexistence at room temperature, (ii) temperature-and field-induced phase transformation to throw light on the atomistic mechanisms associated with the large piezoelectric response of this system. A detailed temperature-dependent dielectric and lattice thermal expansion study proved that the system exhibits a weak dielectric relaxation, characteristic of a relaxor ferroelectric material on the verge of exhibiting a normal ferroelectric-paraelectric transformation. Careful structural analysis revealed that a ferroelectric state at room temperature is composed of three phase coexistences, tetragonal (P4mm)+ orthorhombic (Amm2) + rhombohedral (R3m). We also demonstrate that the giant piezoresponse is associated with a significant fraction of the tetragonal phase transforming to rhombohedral. It is argued that the polar nanoregions associated with relaxor ferroelectricity amplify the piezoresponse by providing an additional degree of intrinsic structural inhomogeneity to the system.

Optical and dielectric relaxor behaviour of Ba(Zr(0.25)Ti(0.75))O(3) ceramic explained by means of distorted clusters

In this work, Ba(Zr(0.25)Ti(0.75))O(3) ceramic was prepared by solid-state reaction. This material was characterized by x-ray diffraction and Fourier transform Raman spectroscopy. The temperature dependent dielectric properties were investigated in the frequency range from 1 kHz to 1 MHz. The dielectric measurements indicated a diffuse phase transition. The broadening of the dielectric permittivity in the frequency range as well as its shifting at higher temperatures indicated a relaxor-like behaviour for this material. The diffusivity and the relaxation strength were estimated using the modified Curie-Weiss law. The optical properties were analysed by ultraviolet-visible (UV-vis) absorption spectroscopy and photoluminescence (PL) measurements at room temperature. The UV-vis spectrum indicated that the Ba(Zr(0.25)Ti(0.75))O(3) ceramic has an optical band gap of 2.98 eV. A blue PL emission was observed for this compound when excited with 350 nm wavelength. The polarity as well as the PL property of this material was attributed to the presence of polar [TiO(6)] distorted clusters into a globally cubic matrix.

Phase-transition studies of Ba(0.90)Ca(0.10)(Ti(1-x)Zr(x))O(3) ferroelectric ceramic compounds

Perovskite-structured Ba(0.90)Ca(0.10)(Ti(1-x)Zr(x))O(3) ceramics were prepared in this work and subsequently studied in terms of composition-dependent dielectric and high-resolution long-range order structural properties from 30 to 450 K. The dielectric response of these materials was measured at several frequencies in the range from 1 kHz to 1 MHz. Combining both techniques, including Rietveld refinement of the X-ray diffraction data, allowed observing that, when increasing Zr(4+) content, the materials change from conventional to diffuse and relaxor ferroelectric compounds, the transition occurring spontaneously at the x = 0.18 composition. Interestingly, this spontaneous transition turned out to be prevented for a further increase of Zr(4+). On the basis of all the dielectric and structural results processed, a phase diagram of this system is presented. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Strain and vacancy cluster behavior of vanadium and tungsten-doped Ba[Zr(0.10)Ti(0.90)]O(3) ceramics

Strain and vacancy clusters behavior of polycrystalline vanadium (V) and tungsten (W)-doped Ba[Zr(0.10)Ti(0.90)]O(3), (BZT:2%V) and (BZT:2%W) ceramics obtained by the mixed oxide method was evaluated. Substitution of V and W reduces the distortion of octahedral clusters, decreasing the Raman modes. Electron paramagnetic resonance data indicate that the addition of dopants leads to defects and symmetry changes in the BZT lattice. Remnant polarization and coercive field are affected by V and W substitution due the electron-relaxation mode. The unipolar strain E curves as a function of electric field reach its maximum value for BZT:2%V and BZT:2%W ceramics. (c) 2008 American Institute of Physics.