Cerium Doped Barium Titanate Research Articles

Electron probe microanalysis of the dopant concentrations in complex perovskite ferroelectrics

Quantitative EPMA-WDS microanalyses were applied for the compositional characterisation of complex perovskite ferroelectrics based on cerium-doped barium titanate, a solid solution between lead-magnesium-niobate/lead-titanate and niobium-doped barium- bismuth-titanate. The analyses were optimized for high analytical sensitivity, precision and an ultimate accuracy of ≈ ± 1 % relative. The inherent problem with the WDS peak overlap of the Ce-Lα1 and Ba-Lβ1,4 spectral lines was solved by introducing overlap-correction methods in order to obtain consistent quantitative results for the Ce-doped BaTiO3. The quantitative results made it possible to obtain accurate chemical formulae for these materials, to determine the solubility of the dopants as well as to define the mode of the dopant incorporation and the charge-compensation mechanisms.

The Direct Measurement of the Photorefractive Grating on Anisotropic Self Diffraction Using Digital Holography

In this paper, the measurement of grating period in photorefractive anisotropic self diffraction by using digital holography technique is proposed. In our experimental setup, He –Ne laser beam with wavelength of 632.8 nm has been separated and then incident on photorefractive cerium doped barium titanate crystal to produce photorefractive index grating. The transmitted probe beam, which contains phase and amplitude has been expanded and recorded on digital camera. To explore the grating periods, both phase and amplitude of the images are reconstructed by numerical process using computer. Then the grating periods in photorefractive anisotropic self diffraction have been measured. The results show grating periods, holograms and their reconstruction.

Fabrication and characterization of cerium doped barium titanate/PMMA nanocomposites

The cerium doped barium titanate (BaTiO3:Ce)/poly methyl methacrylate(PMMA) polymer nano-composites (PNC) were successfully fabricated via solvent evaporation method with microwaves (2.4 GHz) heating. The X-ray diffraction measurements confirm the formation of barium titanate (BT) with crystallite size ranges from 55 to 62 nm. Differential scanning calorimetry study shows that the glass transition temperature (Tg) directly affected by microwaves heat treatment and particle size of filler. The broadband dielectric spectroscopy was employed to investigate the frequency and temperature dependence of the dielectric properties of the nanocomposites in a frequency range from 75 kHz to 5 MHz and temperature range 80–400 K. The introduction of different BT fillers in PMMA enhance the dielectric constant of PNCs drastically and give a smooth response in frequency range mentioned above. The loss factor of the composite can be suppressed by using cerium doped barium titanate filler rather than pure barium titanate filler.

Tunable double-channel filter based on two-dimensional ferroelectric photonic crystals

A tunable double-channel filter is presented, which is based on a two-dimensional nonlinear ferroelectric photonic crystal made of cerium doped barium titanate. The filtering properties of the photonic crystal filter can be tuned by adjusting the defect structure or by a pump light. The influences of the structure disorders caused by the perturbations in the radius or the position of air holes on the filtering properties are also analyzed.

Fabrication and characterization of cerium-doped barium titanate inverse opal by sol–gel method

Cerium-doped barium titanate inverted opal was synthesized from barium acetate contained cerous acetate and tetrabutyl titanate in the interstitial spaces of a polystyrene (PS) opal. This procedure involves infiltration of precursors into the interstices of the PS opal template followed by hydrolytic polycondensation of the precursors to amorphous barium titanate and removal of the PS opal by calcination. The morphologies of opal and inverse opal were characterized by scanning electron microscope (SEM). The pores were characterized by mercury intrusion porosimetry (MIP). X-ray photoelectron spectroscopy (XPS) investigation showed the doping structure of cerium, barium and titanium. And powder X-ray diffraction allows one to observe the influence of doping degree on the grain size. The lattice parameters, crystal size and lattice strain were calculated by the Rietveld refinement method. The synthesis of cerium-doped barium titanate inverted opals provides an opportunity to electrically and optically engineer the photonic band structure and the possibility of developing tunable three-dimensional photonic crystal devices.

An optical switching in two dimensional Ce:BaTiO 3 nonlinear photonic crystal

An optical switching is proposed, which is based on two dimensional nonlinear photonic crystal made of cerium doped barium titanate, and can work in the visible or infrared waveband. The optical nonlinearity originates from the delocalization of the titanium ions in the center of TiO 6 octahedrons. The dynamical shift of the photonic bandgap with pump intensity is calculated on the basis of the optical Kerr effect. It is found that the pump light of 6.7 GW/cm 2 can changes the transmittance of the probe light from 0% to 95% for the first sample in the visible waveband and from 0% to 92% for the second sample in the infrared waveband, respectively. The influences of the disorders caused by the random perturbations in the diameter or the position of the air hole on the optical switching are analyzed.

Laser-diode self-pumped phase conjugation in cerium-doped barium titanate crystal

Abstract The performance of laser-diode (LD) self-pumped phase-conjugation (SPPC) using cerium-doped barium titanate (Ce:BaTiO 3) crystal was investigated. The reflectivity of the phase conjugator against the incident angle and the incident position was measured in two configurations, and the reflectivity could reach as high as 74%. According to the optical path patterns appearing in the crystal, it is believed that the LD-SPPC in Ce:BaTiO 3 is established by a stimulated photorefractive backscattering and four-wave mixing mechanism.

Self-pumped phase conjugation in cerium-doped barium titanate crystal using nanosecond pulses from a laser diode

Summary Self-pumped phase conjugation was performed in a photorefractive cerium-doped barium titanate crystal by nanosecond pulses from a laser diode. The reflectivity of the phase conjugator against the incident angle and the incident position was measured in two configurations. The steady-starte reflectivity of the pulsed phase-conjugate wave increases and the response time decreases as pulse width of incident pulses increases.

Self-Pumped Phase Conjugation in a Ce:BaTiO3 Crystal Pumped with Femtosecond Laser Pulses at 1053 nm Wavelength

Self-pumped phase conjugation in a cerium-doped barium titanate crystal pumped with femtosecond laser pulses at a 1053 nm wavelength was experimentally studied. A reflectivity of a self-pumped phase conjugation as high as 15#x0025; was demonstrated.

Ferroelectric properties of cerium doped barium titanate (BATIO3:CE)

Curie temperature Tc, dielectric constants, absorption coefficients, and lattice constants of ferroelectric BaTiO3:Ce crystals are investigated as a function of cerium concentration. An increase of cell volume with increase doping cerium concentration deduced that the cerium ion is substituted for titanium ion. The absorption edge of crystals moves toward the long wavelength with increasing Ce content. The value of spontaneous polarization and dielectrical constants of BaTiO3:Ce are larger than those in BaTiO3 crystal, and this result is in accord with linear electrooptic coefficient experimental data1

4Pi confocal optical system with phase conjugation

We propose a 4Pi confocal system that incorporates a phase-conjugate mirror into the system to solve the alignment problem and automatically correct the spherical aberration associated with the conventional 4Pi confocal system when observing a thick sample. The proposed system is experimentally verified by use of cerium-doped barium titanate crystal as the phase-conjugate mirror. The full width of the central peak is ~0.15 microm. We also theoretically verify the advantage of automatic correction of the spherical aberration by calculating the intensity distribution at the focal spot.

Mutually pumped phase conjugator with a rainbow configuration in BaTiO_3:Ce crystal using nanosecond pulses

A new type of mutually pumped phase conjugator with a rainbow configuration has been demonstrated experimentally in cerium-doped barium titanate crystal that uses pulsed beams with a pulse width of 3.0 ns and a repetition rate of 40 Hz at a wavelength of 532 nm. The highest phase-conjugate reflectivity was ~24%. The dependence of the phase-conjugate reflectivity on the incident angle and distance, as well as the grating formation time for achieving 1 - e(-1) of equilibrium reflectivity, has been measured.

Photorefractive properties of Ce: BaTiO 3 crystals

We investigate the absorption and photorefractive properties of Ce:BaTiO 3 (cerium doped barium titanate) crystals. The absorption coefficient, electro-optic gain coefficient, and total effective trap density at wavelength 514.5 nm increase systematically with cerium doping concentration. The absorption and the electro-optic gain coefficients exhibit a dependence on the optical intensity. This indicates that there are at least two active photorefractive species. One of these crystals has the highest beam-coupling gain coefficient reported to date, γ=8.06 cm −1 for ordinarily polarized light. The response time of as-grown Ce:BaTiO 3 with 15 ppm cerium is 220 ms at an intensity of 800 mW/cm 2.

High efficiency self-pumped phase conjugation at 633 nm in cerium-doped barium titanate crystals

Photorefractive self-pumped phase conjugation (SPPC) behavoir is examined at 633 nm in cerium-doped barium titane crystals. A reflectivity as high as 86.8% is reported. The buildup times are an order of magnitude faster than the corresponding values in Co: BaTiO 3 and Cu: KNSBN crystals with input powers. A possible mechanism responsible for the high self-pumped phase conjugation reflectivities in the negative incident angle range is discussed.

Dielectric studies of cerium doped barium titanate at different frequencies

Cerium doped barium titanate is prepared by conventional ceramic method. The dielectric studies of Ba1-x Cex TiO3 have been accomplished at room temperature over a frequency range 75 KHz to 30 MHz for x = 0.1 to 0.4 with pure BaTiO3. The measurements of the real and imaginary part of dielectric constants show strong frequency dependence. The relaxation phenomena that take place cane be attributable to the damping of dipole oscillator due to the application of external field. In the present experiment relaxation occurs at the frequency of about - 1MHZ. doi: 10.3329/jbas.v32i1.2445 Journal of Bangladesh Academy of Sciences, Vol. 32, No. 1, 79-85, 2008