Transparent Lead Lanthanum Research Articles

Visible or Near-Infrared Light Self-Powered Photodetectors Based on Transparent Ferroelectric Ceramics.

Transparent ferroelectrics, with promising prospects in transparent optoelectronic devices, have unique advantages in self-powered photodetection. The self-powered photodetectors based on the photovoltaic effect have quicker responses and higher stability compared with those based on the pyroelectric effect. However, the ferroelectric ceramics previously applied are always opaque and have no infrared light-stimulated photovoltaic effect. Thus, it would be very meaningful to design photodetectors based on infrared light-stimulated photovoltaic effect and/or transparent ferroelectric ceramics. In this work, highly optical transparent pristine lead lanthanum zirconate titanate (PLZT) and band gap-engineered Ni-doped PLZT ceramics with excellent piezoelectric/ferroelectric properties were prepared by hot-pressing sintering. Stable and excellent photovoltaic performance was obtained for pristine PLZT and band gap-engineered PLZT. The value of short-circuit current density is at least 2 orders of magnitude larger than those in PLZT reported in previous works. The transparent PLZT and Ni-doped PLZT ferroelectric ceramics are applied as self-powered photodetectors for the first time for 405 nm and near-infrared light, respectively. The devices based on PLZT under 405 nm light exhibit high detectivity (7.15 × 107 Jones) and quick response (9.5 ms for rise and 11.5 ms for decay), and those devices based on Ni-doped PLZT, under near-infrared light filtered from AM 1.5 G simulated sunlight, also exhibit high detectivity (6.86 × 107 Jones) and short response time (8.5 ms), both presenting great potential for future transparent photodetectors.

Effects of Lanthanum Substitution on Dielectric, Ferroelectric and Electro-Optic Properties of Slim-Loop PLZT Ceramics

Highly transparent lead lanthanum zirconate titanate (Pb1−xLax)(Zr0.65Ti0.35)1-x/4O3(x=0.096-0.1) electro-optic ceramics were prepared by the hot pressing method. The ceramics exhibited transparency as high as 67% at 632.8nm (close to the theoretical value). The effects of lanthanum substitution on the phase structure, microstructure, dielectric, ferroelectric, optical and electro-optic properties of PLZT were examined systematically. The XRD results indicated that all the compositions were single perovskite phases, and La substitution decreased the lattice constant and unit-cell volume. The dielectric results showed that the Tmaxand εmaxdecreased with La content increasing. The hysteresis loops showed that the La content reduced saturate polarization (Ps), remnant polarization (Pr) and coercive field (Ec). Moreover, the half-wave voltage and EO coefficient R was enhanced and reduced respectively with increasing La.

Transparent lead lanthanum zirconate titanate (PLZT) ceramic fibers for high-frequency ultrasonic transducer applications

This paper presents fabrication of transparent lanthanum zirconate titanate (PLZT) fibers using extrusion technique. The diameter of the sintered PLZT fiber is about 400-μm, and the fibers exhibit very good transparency. Measured dielectric constant, remnant polarization and coercive field of PLZT fiber were found to be 2340, 22.5-μC/cm2, and 9.8-kV/cm, respectively. The transparent piezoelectric materials may exhibit great potential for Photoacoustic (PA) imaging and hybrid intravascular imaging combining OCT and ultrasound imaging by using the transparent fiber as the path of light propagation and ultrasonic transducer material. In our study, these transparent PLZT fibers were designed to fabricate two types of high-frequency ultrasonic transducers: small aperture single PLZT fiber/epoxy composite and large aperture 1–3 PLZT fiber/epoxy composite ultrasonic transducers. Besides, a 20-μm tungsten wire phantom and the cornea of the porcine eye were also imaged with the 1–3 PLZT fiber/epoxy composite ultrasonic transducer to demonstrate its imaging capability.

Effect of Dy substitution on ferroelectric, optical and electro-optic properties of transparent Pb0.90La0.10(Zr0.65Ti0.35)O3 ceramics

Highly transparent Dy-codoped lead lanthanum zirconate titanate (PLZT) ceramics were sintered from oxide powders by the hot pressing method. The ceramics exhibited a transparency as high as 67% at 632.8nm (close to the theoretical value). The effects of substituting Lanthanum by Dysprosium on the phase structure, microstructure, dielectric, ferroelectric, optical and electro-optic properties of PLZT were examined. The results showed that Dy substitution decreased the coercive field, improved the optical transmittance and electro-optic properties of PLZT ceramics. Moreover, the high half-wave voltage (affecting the working voltage of devices) of PLZT was reduced from 850V to 510V by Dy substitution. Modified PLDZT transparent ceramics are competitive candidate materials for modern optical communication, and the variable optical attenuator (VOA) based on PLDZT exhibited excellent performances.

Electrical transport properties of transparent PLZT ceramics: Bulk and grain boundaries

Transparent lead lanthanum zirconate titanate (PLZT) ceramics were investigated by ac impedance spectroscopy at temperatures between 300 and 500 °C under different oxygen partial pressures with the purpose of addressing the role of boundary effects on the electrical conduction properties of this compound. It is found that in spite of the high lanthanum content, holes are the dominating electronic charge carriers leading to p-type conductivity in oxidizing conditions. The grain boundaries reveal a blocking behavior (holes depletion), which is explained in the framework of the space charge concept. A positive space charge potential of 0.23 V is obtained.

Electrical field dependence of thermo-optical parameters in transparent lead lanthanum zirconated titanate ceramic: Thermal lens measurements

In this work, thermal lens spectroscopy was used to analyze the thermo-optical properties of the transparent ceramic lead lanthanum zirconated titanate or PLZT 10/65/35 as a function of the external electric field, from 0 to 1200 kV/m. The results show that when increasing the electrical field in the sample, the temperature coefficient of optical path length presented parallel and perpendicular components. For the parallel component, the electrical field makes this parameter alternate from positive to negative and from negative to positive and so on. This behavior as a function of an external electric field may be useful in the development of electro-optical devices with this transparent ceramic.

ChemInform Abstract: Fabrication of Transparent Lead Lanthanum Zirconate Titanate (PLZT) Ceramics from Fine Powders by Two-Stage Sintering.

ChemInform Abstract: Fabrication of Transparent Lead Lanthanum Zirconate Titanate (PLZT) Ceramics from Fine Powders by Two-Stage Sintering.

Constitutive equations for 0-3 polarized PLZT actuators

This article presents constitutive equations of transparent lead lanthanum zirconate titanate (PLZT) materials poling along thickness direction or with 0-3 polarization. Discussed first are the Beer’s law of light transmission in transparent solid and the photovoltaic current density in PLZT materials. Formulas for field strength and electrical potential between two electrodes of a PLZT wafer are then derived from the basic photovoltaic equations. By superposing the photovoltaic and the converse piezoelectric effects, we formulate a novel expression for photo-induced strain that is nonlinearly dependent of incident light intensity and varies with light penetration depth in through-thickness direction. On the basis of the derived photo-induced strain, linear and nonlinear constitutive equations of 0-3 polarized PLZT actuators are formulated. The present model is validated by using the available experimental data in the literature. By using the present model with an exponential variation of strain through the thickness, closed-form solutions for the equivalent loads acting on a PLZT unimorph, bimorph and intelligent beam are obtained and then compared with numerical results available in the literature.

Quasistatic dielectric and strain characterization of transparent relaxor ferroelectric lead lanthanum zirconate titanate ceramics

The relative permittivity and dielectric loss tangent of transparent lead lanthanum zirconate titanate (PLZT) (9.5/65/35) and (9.0/65/35) ceramics were measured as a function of temperature, ranging from −60 to 100 °C, and as a function of frequency, ranging from 0.12 to 5000 kHz. Diffuse maxima were observed in the complex permittivity plots of both PLZT compositions. These maxima correspond to phase transitions from ferroelectric to paraelectric and finally to cubic in the PLZT crystal structure. Second, a Sawyer–Tower circuit was used to determine the electric displacement of each ceramic composition as a function of a dc bias field, ranging from −1.7 to 1.7 MV/m. Third, a Polytech vibrometer was used to measure the longitudinal ac strain response of (9.5/65/35) and (9.0/65/35) PLZT ceramics under various dc bias and ac electric fields with a 120 Hz driving frequency. A maximum piezoelectric strain of 0.8×10−3 m/m occurred for a 0.64 mm thick (9.5/65/35) PLZT at 1.1 MV/m dc and 1.09 MV/m ac peak to peak, and 1.3×10−3 m/m for a 0.54 mm thick (9.0/65/35) PLZT at 1.4 MV/m dc and 0.68 MV/m ac peak-to-peak. Fourier analysis was performed on the raw vibrometer data and the strain response at the second, third, and fourth harmonics were obtained as a function of dc and ac fields. Finally, the measured data were fitted to a theoretical model and the material coefficients for these PLZT compositions were obtained.

Analysis of the dynamics of upconversion in erbium-doped transparent lead lanthanum zirconate titanate ceramic

The absorption and upconversion fluorescence spectra of Er3+ ions in Er3+ doped transparent lead lanthanum zirconate titanate(PLZT)ceramic were measured at room temperature. The radiative transition probabilities of the Er3+ ions were calculated using the absorption spectrum of Er3+ doped PLZT. Strong upconversion emission was observed in the upconversion luminescence of Er3+ doped PLZT. The green emission intensities at 540nm and 564nm were stronger than the red emission intensity at 678nm. The upconversion rate equations describing the dynamic process of the system have been deduced. The upconversion coefficients were estimated by numerically solving the rate equations and fitting the simulated curves to the measured data. The coefficients C22and C33 obtained are 091×10-18cm3/s and 1823×10-18cm3/s, respectively. The results show that evident upconvesion phenomenon can be observed in Er3+: PLZT transparent ceramics, which is consistent with our observation.

Structural and spectroscopic properties of rare-earth (Nd3+, Er3+, and Yb3+) doped transparent lead lanthanum zirconate titanate ceramics

This work presents the structural and spectroscopic characterization of transparent lead lanthanum zirconate titanate ceramics doped with Nd3+, Er3+, or Yb3+ ions. High optical quality samples presenting the perovskite structure were prepared through a mixed oxides method followed by conventional sintering or uniaxial hot pressing. Absorption and luminescence spectra were measured, and radiative emission parameters were calculated for Nd3+- and Er3+-doped samples. The results indicate the potential of these polycrystalline host–ion combinations for the construction of diode-pumped lasers in the near-infrared region.

Fabrication of transparent lead lanthanum scandium niobate ceramics by two-stage atmosphere sintering

Transparent lead lanthanum scandium niobate (PLSN) ceramics were fabricated from fine powders using a two-stage atmospheric sintering technique. A method for preparing clear aqueous solutions with lead, lanthanum, scandium and peroxo–niobium complex ions has been developed by mixing a niobium precursor solution with the corresponding nitrates. The coprecipitation process of the solution produced chemically homogeneous powders. Biaxially pressed green pellets were sintered in an oxygen gas in an alumina setter containing an atmosphere powder at 1100 °C and were then reheated in air. Transparent ceramics with an average grain size of 0.54 μm was obtained.

Transparent Lead Lanthanum Zirconate Titanate Ceramics Derived from Oxide Mixture Via a Repeated Annealing Process

Lead lanthanum zirconate titanate (PLZT9/65/35) ceramics were prepared from their oxide mixture via reactive sintering without involving a calcination step. PLZT ceramics sintered at 1000 °C for 4 h possessed a grain size of 3–4 μm, a dielectric constant of 3670, a dielectric loss of 0.033 at 1 kHz, and a remnant polarization of 5.7 μC/cm2 and coercive field of 4.6 kV/cm, respectively. Transparent PLZT ceramics were obtained by annealing the sintered samples at 1125 °C for 6 h repeatedly for 4 times without using hot pressing or oxygen flow. The grain size of PLZT ceramics increased to 4–6 μm, with dielectric constant of 5187 and dielectric loss (1 kHz) of 0.036, and remnant polarization of 11 μC/cm2 and coercive field of 5.3 kV/cm. The transparent PLZT ceramics demonstrated a transmittance of 42% at a wavelength of 550 nm.

Fabrication of Optically Transparent Lead Lanthanum Zirconate Titanate ((Pb,La)(Zr,Ti)O3) Ceramics by a Three‐Stage‐Atmosphere‐Sintering Technique

An easy technique has been developed to fabricate optically transparent lanthanum‐modified lead zirconate titanate (PLZT) ceramics. This technique consists of three stages: (1) sintering in an oxygen atmosphere, (2) elimination of pores in a carbon dioxide atmosphere, and (3) elimination of oxygen vacancies in an oxygen atmosphere. The carbon dioxide atmosphere enhances the diffusion of oxygen from the pores to outside the sintered body. The experimental results reveal that use of a carbon dioxide atmosphere effectively decreases residual pores and improves optical transmittance. From commercially available raw powders, an optical transmittance of 51% (wavelength of 550 nm) can be achieved for 0.7 mm thick polished PLZT9/65/35 ceramics using a carbon dioxide atmosphere, whereas the value is only 34% without a carbon dioxide atmosphere. The advantage of this technique is that PLZT ceramics having high optical quality can be obtained using conventional sintering tools.

Microcrack clouds in fatigued electrostrictive 9.5/65/35 PLZT

Abstract The formation of microcracks during cyclic bipolar fatigue is shown for purely dielectric electrostrictive 9.5/65/35 transparent lead–lanthanum–zirconate–titanate (PLZT). The optically transparent material allows for the direct observation of broken grain facets. The maximum reached polarisation decreases by 30% after 3×10 6 cycles. The formation of microcrack clouds at the specimen edges and at macroscopic cracks are shown. No cracks were found in sample regions without obvious flaws present. By estimating the cracked volume, comparisons with FEM from previous studys allow to calculate the influence of the observed cracking on the polarization. As a consequence, the observed microcracks are considered to be mainly responsible for polarisation degradation.

2.79 μm erbium laser with lead–lanthanum zirconate titanate ceramics electro-optic Q-switching output coupler

Highly refractive and transparent lead–lanthanum zirconate titanate (PLZT) ceramics are used for an output coupler of the erbium yttrium scandium gallium garnet laser (λ=2.79 μm) that simultaneously serves as the laser electro-optic Q switch. The optical aperture of such a dual-function PLZT element was 6×6 mm2 and the thickness was 3 mm. For Q switching, short ≈3 μs negative voltage pulses (1500–1800 V) were applied to the positively direct current biased (≈1400 V) PLZT element. Single-pulse lasing with a pulse half width of 160–170 ns was observed at short and long delays of the Q switch with respect to the pump flash. The highest output energy of 20–22 mJ within 1.5–2.5 μs, consisting of two or three pulses with 130 ns half width was obtained at an intermediate delay of 90–110 μs.

Electro-optic focusing system for a high-density optical disk

We have developed an electro-optic cell as a fine-adjustment focusing system for an optical disk. The cell is fabricated from transparent lead lanthanum zirconate titanate ceramic and has concentric-patterned indium tin oxide electrodes. The electro-optic cell can generate a relative phase shift in the pupil function. We have confirmed, theoretically and experimentally, that the phase shift induces a change in focal position that is as much as twice the focal depth without degrading the region near the main lobe of the point-spread function.

Fabrication of Transparent Lead Lanthanum Zirconate Titanate Ceramics from Fine Powders by Two‐Stage Sintering

Transparent lead lanthanum zirconate titanate (PLZT) ceramics were fabricated from fine powders using an inexpensive two‐stage sintering technique. The powders were prepared by hydrolysis from low‐cost inorganic precursors. In the two‐stage sintering method, uniaxially pressed green pellets were densified to nearly theoretical values in an oxygen gas atmosphere during the first‐stage sintering, at 1000°C for 1 h, and then residual, free lead oxide in the pellets was removed by second‐stage sintering at 1100°C for 12 h. Transparent ceramic with an average grain size of 1.6 μm and a porosity of 1.3% was obtained. The transparency and dielectric characteristics of the present samples were compared with those of hot‐pressed samples: The study of the polarization–field hysteresis loops of the present samples yielded a remanent polarization of 6.8 μC/m2 and a coercive field of 1.6 kV/cm. The low coercive field of PLZT ceramics could potentially reduce the driving voltage of electrooptic devices in many applications.

Photographic image storage in ion implanted PLZT ceramics

Photographic images can be stored in transparent lead lanthanum zirconate titanate (PLZT) ceramics using near-UV light with photon energies near the band gap energy of 3.42 eV. Coimplanting inert ions, e.g., Ar, Ne and He, into the surface exposed to image light can increase near-UV photosensitivity by a factor of almost 10 4, with no degradation of image quality, so that the exposure energy threshold is reduced from ∼ 100 mJ/cm 2 to ∼ 10 μJ/cm 2. Coimplanting chemically active and inert ions, e.g., Al or Ne, can result in similar improvement of the extrinsic (visible light) photosensitivity and in an essentially flat photoresponse from about 400 to 600 nm. In addition, thermal diffusion of Al followed by Ne implantation yield photosensitivity increases in the near-UV comparable to the best results obtained to date with ion implantation. The Al-diffused plus Ne-implanted samples also have the highest photosensitivity obtained to date in the blue region of the visible spectrum. Ion implanted, or Al-diffused plus Ne implanted, PLZT is now the most sensitive, nonvolatile but selectively erasable image storage medium known to exist.