Slow crystallization process from amorphous PbTiO3

The effect of isothermal annealing of amorphous PbTiO₃ at a temperature below the crystallization temperature, T_crys, has been investigated. Time dependent dielectric constant in the annealing process has been observed. From the experimental results, both the existence of the glass transition temperature, T_g, and the steadiness of dielectric constant at room temperature have been established.     

Electro-optic properties of liquid suspension of pbTio3 ultrafine powders

polar PbTio₃ ultrafine powders derived form Sol-Gel process is suspended in many liquid mediums by ultrasonic wave. In this paper, electric field-induced light transmission and scattering of PbTiO₃ ultrafine powder suspension has been investigated. The effect of powder shapes, radius of powders, concentration of suspension and dispersion medium on light scattering and transmission is reported. The change of transmission light reaches 100, while for the scattering light reaches 30%. Electric field-induced change of refractive index of PbTiO₃ powder suspensions has also been observed.     

Characterization of PbTiO3 crystallites in-situ confined grown in amorphors silica

PbO-TiO₂-SiO₂ glass-ceramic with PT crystallites in-situ confined grown from silica matrix has been synthesized by sol-gel method. Crystallization process of PT crystallites is studied by XRD and DTA. From XRD data, it has been found that the c axis length and c/a ratio of PT tetragonal structure decrease obviously with increase of silica content. The phase transition temperature of PbTiO₃ nanocrystallites from tetragonal to cubic and the transition latent heat all decrease dramatically. The strain and crystal size of the confined grown PT crystallites are calculated by the method of Wilson and Scherrer respectively. The special confined environment where crystal grains grow and the size effect are thought to be the reason of the feature of the PbTiO₃ in silica.     

Lattice dynamics and conductivity of PbTiO3: La, Cu

We have grown powders and ceramics of Lead Titanate (PbTiO₃) doped with Lanthanum and Copper. The incorporation of Cu ions does not change the lattice properties of PbTiO₃: La. On the other hand, we demonstrate that the conductivity properties of PbTiO₃: La, Cu may be swept over 12 orders of magnitude.     

Theory of anisotropic oxygen polarizability in the tetragonal phase of PbTiO3

The optical anisotropy of the tetragonal phase of PbTiO₃, is discussed according to the point-dipole approach. In this microscopic model, we have taking into account of the electronic polarization and the lattice deformation and it is shown that anisotropic electronic polarizabilities are the dominant source of the optical properties of PbTiO₃. This anisotropy is attributed to the O_z, oxygen ion and it is due to the Ti-Oz and Pb-O_z overlap in the tetragonal phase.

By analyzing the optical refractive index data of PbTiO₃ at 0.589 μm, we have determined the temperature dependence of the oxygen polarizabilities. Based on the dispersion data of the refractive index of PbTiO₃, the dispersion of the oxygen polarizabilities are similarly calculated at room temperature.     

Metalorganic chemical vapor deposition of ferroelectric PbTiO3 thin films on amorphous substrate

PbTiO₃, thin films have been grown on amorphous glass substrate by metalorganic chemical vapor deposition. The as-deposited films were investigated using x-ray diffraction and scanning electron microscopy techniques. PbTiO₃, thin films fabricated were polycrystalline with highly c-axis-oriented textures. The films were dense-packed and showed uniformly distributed fine grain size. Growth mechanism and domain structure of the ferroelectric thin films on amorphous substrate were also studied.     

La-, K- and Nb-doped 0.90(Bi0.5Na0.5TiO3)–0.10PbTiO3

Lanthanum, Potassium and Niobium have been selected as cation dopants to modify the relaxor characteristics of 0.90(Bi_0.5Na_0.5TiO₃)–0.10PbTiO₃. The experimental results show that La lowers the phase transition temperatures and decreases the grain size. In contrast, the grain size of K-doped composition tends to increase. Furthermore, the maximum of dielectric permittivity and the Curie temperature increase as compared to those of La-doped material. La can improve the broadness of dielectric permittivity of 0.90(Bi_0.5Na_0.5TiO₃)–0.10PbTiO₃. However, Nb is a better promising dopant for enhancing the relaxor behavior for this composition.     

Soft piezoelectric (1-x)Pb(Sc1/22Ta1/2)O3-(x)PbTiO3 ceramics with high coupling factors and low QM

The piezoelectric behavior of materials from the (1-x)Pb(Sc_1/22Ta_1/2)O₃-(x)PbTiO₃ solid solution system has been investigated. The [x = 0.45] composition in particular has exhibited an outstanding piezoelectric response [d₃₃ = 650 (pC/N). k_t = 0.5, k_p = 0.61. k₃₃ = 0.73] and a low mechanical quality factor [Q_M = 30]. These features make it a promising candidate for a variety of piezoelectric sensor applications. The difficulties involved in effectively poling a bar sample and a means to avoid these problems are also addressed.     

Theory of ferroelectricity in the tetragonal phase of PbTiO3 due to the lattice deformation

The physical origin of the ferroelectricity in the tetragonal phase of PbTiO₃ is discussed quantitatively from the dipole-dipole interaction caused by the strong local field acting on the constituent ions. In this microscopic model, only Pb and Ti ions are assumed to have the spontaneous shift. The cubic-tetragonal phase transition in PbTiO₃ is also analysed. It is found that the ferroelectricity and the order of the phase transition are in good agreement with the experimental data.     

Piezoelectric properties of Pb(Mn1/3Nb2/3)O3–PbZrO3–PbTiO3 ceramics with sintering aid of 2CaO–Fe2O3 compound

Since the electromechanical devices move towards enhanced power density, high mechanical quality factor (Q_m) and electromechanical coupling factor (k_p) are commonly needed for the high powered piezoelectric transformer with Q_m≥2000 and k_p=0.60. Although Pb(Mn_1/3Nb_2/3)O₃–PbZrO₃–PbTiO₃ (PMnN–PZ–PT) ceramic system has potential for piezoelectric transformer application, further improvements of Q_m and k_p are needed. Addition of 2CaO–Fe₂O₃ has been proved to have many beneficial effects on Pb(Zr,Ti)O₃ ceramics. Therefore, 2CaO–Fe₂O₃ is used as additive in order to improve the piezoelectric properties in this study. The piezoelectric properties, density and microstructures of 0.07Pb(Mn_1/3Nb_2/3)O₃–0.468PbZrO₃–0.462PbTiO₃ (PMnN–PZ–PT) piezoelectric ceramics with 2CaO–Fe₂O₃ additive sintered at 1100 and 1250 °C have been studied. When sintering temperature is 1250 °C, Q_m has the maximum 2150 with 0.3 wt.% 2CaO–Fe₂O₃ addition. The k_p more than 0.6 is observed for samples sintered at 1100 °C. The addition of 2CaO–Fe₂O₃ can significantly enhance the densification of PMnN–PZ–PT ceramics when the sintering temperature is 1250 °C. The grain growth occurred with the amount of 2CaO–Fe₂O₃ at both sintering temperatures.     

Dielectric Properties and Relaxor Behavior of PIN Based System

Several compositions in the two PIN based systems (1-x)Pb(In_0.5Nb_0.5)O₃-(x)PbTiO₃ and (0.8-x)Pb(In_0.5Nb_0.5)O₃-(x)PbTiO_3-0.2BaTiO₃ (x = 0.0, 0.1, 0.2 and 0.3) were synthesized via the wolframite method. Dielectric properties were measured in the frequency range between 100 Hz and 100 kHz and were analyzed for understanding relaxor behavior in the system. The temperature dependence of the dielectric properties was analyzed by studying the deviation from the Curie-Weiss law while the frequency dependence of the dielectric properties was analyzed by the Vogel-Fulcher relation. The results showed that the addition of BT increased the dielectric constant and decreased the shift of the maximum dielectric constant temperature (T_m) of (1-x)PIN-(x)PT compositions. Finally, the analysis also confirmed that, when added to PIN, PT decreased and BT increased the relaxor behavior of the PIN-based ceramics.     

Bulk photovoltaic effect in the PbTiO3 -La(Zn2/3 Nb1/3)O3 solid solution ceramics

The dependences of the bulk photovoltaic effect on the composition fraction x, temperature, and on illumination wavelength have been investigated in the (1-x)PbTiO₃-xLa(Zn_2/3Nb_1/3)O₃ solid solution ceramics. The composition dependence of the photovoltaic current J_ph shows a very similar tendency to that of the remanent polarization P_r, suggesting that J_ph is directly related with P_r. On the contrary, the variation of the photocurrent with temperature measured in a sample with x=0.105 reveals an anomalous peak just below the Curie temperature. These characteristics are discussed in comparison with the ceramic BaTiO₃ data by Brody.     

Ferroelectricity in SrTiO3: Pb

Dielectric study of phase transitions in SrTiO₃ -PbTiO₃ ceramic samples with PbTiO₃ content x ranging from 0.002 up to 0.3 is reported. It is shown that there is a ferroelectric phase transition for x value as low as 0.005. At low x the transition temperature T_C varies as (x-x_c)^1/2 with x_c = 0.002.     

Positions of the Morphotropic Phase Boundaries in Solid Solutions of Lead Titanate

The morphotropic phase boundary, which, separates the tetragonal and rhombohedral ferroelectric solid solutions in the (1 - x)PbTiO₃ +xPbBO₃ and (1 - x)PbTiO₃ + xPb(B', B')O₃ systems, is almost always close to x = 0.5, when the relation of numbers of the smaller Ti and larger B or (B', B') ions is near to 1:1. Then, the smaller and larger ions can be ordered chequerwise. As the main cause of the morphotropic boundary existence, the paper considers growth of the B, B', B' ion sizes at increase of x. Nevertheless, it is assumed that its appearance can be triggered by the ion ordering, expected at x ≈ 0.5. Possibly, such an ordering could assist also to formation of some intermediate monoclinic ferroelectric phase.     

Critical exponents of the dielectric constants in diffused-phase-transition crystals

The critical exponent γ in the relation between the dielectric constant and temperature (1/ε - 1/ε_m = C'^-1×(T - T_m)^γ) has been determined precisely for relaxor ferroelectrics Pb(Mg_1/3 Nb_2/3)O₃, Pb(Zn_1/3 Nb_2/3)O₃ and a related solid solution 0.88Pb(Zn_1/3 Nb_2/3)O₃-0.12PbTiO₃, as well as for normal ferroelectrics BaTiO₃ and K(Ta_0.55Nb_0.45)O₃. A high correlation of the γ value with the phase transition diffuseness has been found empirically. Moreover, this γ value is very close to another critical exponent γ^* which is defined in the relation between the dielectric constant and hydrostatic pressure (1/ε - 1/ε_m = C^*-1(p - p_m)^γε).     

Large hydrostatic piezoelectric constant and temperature dependence of the piezoelectric properties of Bi(NiTi)1/2O3: PbTiO3 ceramics

Large hydrostatic piezoelectric coefficient, d_h - 111 pC/N, for compositions in the system (1-x) Bi(NiTi)_1/2O₃: (x) PbTiO₃[BPNT] has been reported in this paper. Temperature dependencies of the dielectric, elastic, and piezoelectric properties of two compositions, x = 0.40 and x = 0.50, around the morphotropic phase boundary of Mn⁺² doped BPNT ceramics have been studied. Room temperature dielectric hysteresis loops with P_r = 37.86 μC/cm² and E_c = 25.75 kV/cm were observed for x = 0.40. Electromechanical coupling factors, k_p = 32.5%, k₃₁ = 19.7%, and k_t = 57.1% and piezoelectric constants, d₃₃ = 250 pC/N, d₃₁ = -67 pC/N, and d_h = 111 pC/N were measured in the BPNT-40 composition. The hydrophone figure of merit, d_hg_h ≈ 1055 × 10^-15 m²/N was calculated from these measurements.     

Preparation and microstructure analysis of Fe-doped PbTiO ceramic

Fe-doped PbTiO₃ (PT) powder and bulk materials were prepared successfully by sol-gel technique and a subsequent sintering process using Fe (C₅H₅)₂ as a dopant agent. The effects of pH and temperature on the Fe-doped PT system were investigated. Thermogravimetry/differential thermal analysis (TG/DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the composition and the microstructure of the PT ceramics. The results indicated that the thermal decomposition of xerogel included three stages: volatilization of adsorption water and organic composition, oxygenolysis of n-butyl and acetate, and transformation of the crystalline phase. Well-stabilized collosol and gel could be obtained at 60°C and pH = 4.5. It was found that PbTiO₃, PbFe₂O₄, and TiO₂ crystalline appeared in the Fe-doped PT system when the mass fraction of the dopant Fe was 0.03%. Furthermore, from STM analysis, it could be seen that the grain size of doped PT ceramics was homogeneous and about 1–2 ?m, and the pore of the PT ceramic was small. As a result, the PT ceramic had high tightness.     

Dieletric and relaxation behaviors of (PbMg1/3Nb2/3O3)0.67(PbTiO3)0.33 single crystal

Dielectric permittivity along the [111] direction has been measured as a function of temperature for a relaxor ferroelectric single crystal (PbMg_1/3Nb_2/3O₃)_0.67(PbTiO₃)_0.33 (PMN-33%PT). A sharp ferroelectric phase transition was observed near 425 K and 429 K for cooling and heating processes, respectively. As temperature decreases, a diffuse phase transition (which begins near 330 K upon cooling) was detected. In addition, the nature of the thermal hysteresis for the dielectric permittivity confirms that these transitions (near 330 and 425 K upon cooling) are diffuse first-order and first-order, respectively. The frequency-dependent dielectric data ε'₁₁₁ (ƒ, T) prove the existence of an electric dipolar relaxation process between 350 and 400 K. The activation energy, the Vogel-Fulcher temperature and attempt frequency corresponding to this relaxation process are also calculated.     

Dielectric, pyroelectric and piezoelectric properties of calcium-modified lead magnesium tantalate-lead titanate ceramics

Dielectric, pyroelectric and piezoelectric properties of relaxor ferroelectrics in solid solution, formulated 0.65(Pb_1-xCa_x)(Mg_1/3Ta_2/3)O₃-0.35PbTiO₃, have been investigated. Complete single-phase perovskite with high density was obtained with all samples fired at 1250°C. The Curie temperature and pyroelectric peak temperature decrease almost linearly as the amount of Ca in the compositions increases. The transition temperature of the solid solutions can easily be controlled by Ca additions in the PMT-PT. Dielectric, pyroelectric and piezoelectric constants achieved maximum values for x=0.02. Compositions near 0.65PMT-0.35PT-0.12Ca have been identified to have high dielectric constants(∼ 15000) and low dissipation factors(∼ 0.015) near room temperature.     

Long-term aging characteristics of high coupling factor PMS piezoelectric ceramics

The aging characteristics of high coupling factor piezoelectric ceramics (K_p = 63%) in the PMS system [x Pb(Mn_1/3Sb_2/3)O₃-y PbTiO₃-z PbZrO₃, where x + y + z = 11 have been measured for the duration of 14 years. The results indicate that the aging properties of the ceramic are very good. The piezoelectric and dielectric constants of the material stabilized and remained at constant levels one month after the time of poling. In a comparison of the parameters measured after 14 years against those measured one month after poling, the resonance frequency f_r increased by 0.1%, the antiresonance frequency f_a decreased by 0.2%, the planar coupling factor K_p decreased by 0.5%, and the dielectric constant, mechanical and dielectric quality factors showed no noticeable change. It is anticipated that this piezoelectric ceramic may be used more widely in different devices.