Ba0.77Ca0.23TiO3 Research Articles

Study on the magnetoelectric effect, ferroelectric and optical investigation of (1−x) BCT + x NZLFO multiferroic composite

AbstractThis study investigates the magnetoelectric coupling effect in dual‐phase multiferroic composites prepared using a solid‐state reaction method. The composites were fabricated with the formula (1−x)Ba₀.₇₇Ca₀.₂₃TiO₃(BCT) + xNi₀.₆Zn₀.₂₅La₀.₁₅Fe₂O₄(NZLFO), where x varied from 0% to 100% in 10% increments. Ca‐doped BaTiO₃ served as the ferroelectric phase, while La‐doped Ni–Zn ferrite acted as the ferromagnetic phase. The effects of varying ferrite content (x) on structural, optical, ferroelectric, electrical, and magnetoelectric properties were comprehensively analyzed. X‐ray diffraction (XRD) with Rietveld refinement revealed a spinel cubic structure for the ferrite phases and a tetragonal structure for the perovskite phases. The study observed a moderate influence of ferrite concentration on the lattice parameters of BCT and an opposing effect on the lattice parameters of NZLFO. Optical measurements indicated higher light absorption in the visible range compared to the UV region and wide optical bandgap. Magnetic properties, characterized by saturation magnetization, exhibited a dependence on temperature, with a Curie temperature (Tc) of 700 K. Electrical resistivity displayed a maximum at x = 50% and remained constant at high frequencies. The study also confirmed the presence of electric polarization induced by a magnetic field, with the highest magnetoelectric coefficient observed at x = 10%. These findings demonstrate the successful fabrication of dual‐phase multiferroic composites with tunable properties through controlled ferrite content. The observed magnetoelectric coupling suggests potential applications in multifunctional devices.

Photoluminescence critical behavior in Er3+ doped Ba0.77Ca0.23TiO3 ceramic

We developed a non-contact and non-destructive method to detect Curie point (TC) in Er3+ doped Ba0.77Ca0.23TiO3 (BCT) ferroelectric ceramic. Through investigating the photoluminescence (PL) spectra of Er3+ doped BCT ceramic we found that PL characteristics in ferroelectrics demonstrates critical behavior around TC. Both intensity and peak positions of the Stark sub-peaks originating from 4S3/2 to 4I15/2 transition change dramatically, and can be fitted with two different lines below and above TC. The inflection points of the PL characteristics are at the same temperature of 381(1) K, and coincident with the TC (381 K) determined by the dielectric temperature spectrum.

A naturally grown three-dimensional nonlinear photonic crystal

Nonlinear frequency conversion via three-dimensional (3D) quasi-phase matching (QPM) process is experimentally realized based on a Ba0.77Ca0.23TiO3 (BCT) crystal. The ferroelectric domains in BCT crystal are observed, and the results reveal that the antiparallel domains distribute in three dimensions and can provide 3D reciprocal lattice vectors for QPM processes. Broadband petal-like second-harmonic patterns are achieved, which are well consistent with the theoretical quasi-cubic model of 3D nonlinear photonic crystals. Our work not only promotes the development of QPM technique but also builds a platform for 3D nonlinear optics and quantum optics.

Aging effect of Mn-doped Ba0.77Ca0.23TiO3 ceramics

In this work, to investigate the aging effect of perovskite ferroelectrics, lead-free Ba0.77Ca0.23TiO3 (BCT), (Ba0.77Ca0.23)0.99Mn0.01TiO3 (BCT-A), and Ba0.77Ca0.23Ti0.99Mn0.01O3 (BCT-B) ceramics were prepared. The aging effect on the ferroelectric, piezoelectric and dielectric properties were investigated. The present study shows that the substituted sites in BCT have significant influence on the aging effect. Double hysteresis loop is observed in B-site substituted BCT-B ceramics. However, no obvious aging effect is obtained in the BCT-A ceramics. The aging in the poled BCT-B can increase the Curie temperature, mechanical quality factor, and decrease the piezoelectric constant, electromechanical coupling coefficient, dielectric loss and dielectric constant. The aging mechanism is explained in this study.

The enhanced piezoelectric performance of Bi1/2Na1/2TiO3–BaTiO3 ceramics by Ba0.77Ca0.23TiO3 substitution

In this study, lead-free (1−x)Bi0.47Na0.47Ba0.06TiO3–xBa0.77Ca0.23TiO3 (BNBT–xBCT, x=0–0.12) ceramics were fabricated by ordinary ceramic sintering technique. The results show that Ba0.77Ca0.23TiO3 (BCT) has diffused into Bi0.47Na0.47Ba0.06TiO3 (BNBT) lattices to form a new solid solution BNBT–xBCT. Moderate substitution of BCT in BNBT–xBCT (x⩽0.01) ceramics can enhance the piezoelectric and ferroelectric properties; meanwhile, depolarization temperature of the ceramics does not decrease. BNBT–0.01BCT ceramic exhibits the best piezoelectric properties and strongest ferroelectricity: piezoelectric coefficient d33=178 pC/N; electromechanical coupling factors kt=50% and kp=27%; quality factor Qm=131; remnant polarization Pr=36μC/cm2; coercive field Ec=24.5kV/cm. The piezoelectric properties, ferroelectric characteristics and depolarization mechanism of the ceramics are investigated and discussed.

Piezoelectric and dielectric properties of Bi0.5Na0.5TiO3–Bi0.5K0.5TiO3–Ba0.77Ca0.23TiO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics (1 − x)Bi0.5(Na0.84K0.16)0.5TiO3–xBa0.77Ca0.23TiO3 (BNKT–xBCT, x = 0–0.04) were synthesized by conventional solid-state reaction method. The piezoelectric, dielectric, and ferroelectric characteristics of the ceramics are investigated and discussed. The XRD results show that Ba0.77Ca0.23TiO3 (BCT) has diffused into Bi0.5(Na0.84K0.16)0.5TiO3 (BNKT) lattices to form a new solid solution. It is shown that moderate additive of BCT (x ≤ 0.025) in BNKT–xBCT ceramics can enhance their piezoelectric and ferroelectric properties. Three dielectric anomalies are observed in BNKT–xBCT (x ≤ 0.03) ceramics. The piezoelectric measurements and P–E hysteresis loops reveal that BNKT–0.025BCT ceramic has the highest piezoelectric performance and strongest ferroelectricity in all the samples. Piezoelectric constants d 33, k p, and k t of 175 pC/N, 29.1, and 54% are, respectively, achieved. Remnant polarization P r and coercive field E c reach 28.3 μC/cm2 and 24.2 kV/cm, respectively.

Parametric holographic scattering processes in photorefractive barium–calcium titanate crystals

We investigate light-induced parametric holographic scattering in photorefractive Ba0.77Ca0.23TiO3 (BCT) crystals illuminated with two coherent pump beams. On a screen behind the crystal we observe different scattering patterns which we attribute to certain phase-matching conditions. This allows for the identification of the involved four-wave mixing processes. We discuss the influence of space charge field limitations and the magnitude of the involved electrooptic tensor elements on the appearance of parametric scattering processes. In this context we compare our results with observations in other crystals.

Some aspects of fanning, self-focusing and self-defocusing in a photorefractive Ba0.77Ca0.23TiO3crystal

We present some aspects of wave self-focusing and self-defocusing in a photorefractive Ba0.77Ca0.23TiO3 (BCT) crystal without external electric field and without background illumination. The effects depend on the cross-section of the input beam. We show that by decreasing the diameter of the input beam from 730 µm the fanning effect disappears at 150 µm. A symmetrical self-focusing is observed for input diameters from 150 µm down to 40 µm and a symmetrical self-defocusing for input diameters from 40 µm down to 20 µm. The 1D self-trapping is detected at 65 µm in BCT. Light intensity and wavelength are correspondingly 3 mW and 633 nm.

Ba0.77Ca0.23TiO3 (BCT): a new photorefractive material to replace BaTiO3 in applications

The most popular photorefractive material BaTiO 3 suffers from a crippling defect when applications are considered: its phase transition around room temperature that can destroy its photorefractive characteristics, if not the crystal itself. Some years ago, University of Osnabrück [1] , proposed and successfully grew Ba 0.77 Ca 0.23 TiO 3 an alloy derived from BaTiO 3 , in which the phase transition was pushed away towards low temperature. The remaining question was then: does this new material keep the good photorefractive properties that made the success of BaTiO 3 ? We will present here some theoretical and experimental results that allow us to answer this question and that show that despite some differences in the photorefractive properties between BaTiO 3 and BCT, the new crystal is an extremely promising materials for photorefractive applications, such as phase conjugation or dynamic holographic intracavity laser mode selection.

Luminescence of Ba0.77Ca0.23TiO3:Cr

Photoluminescence and optical absorption of nominally pure and Cr-doped (70–350ppm) congruently melting Ba0.77Ca0.23TiO3 (BCT) single crystals were examined in the 300–800nm spectral and 5–300K temperature region. Undoped BCT shows a fundamental optical absorption edge at ∼3.2eV for light polarized along the tetragonal C4 axis and at ∼3.1eV—normal to the C4 axis at RT. Interband excitation with λexc=350nm results in a wide-band structured visible emission with broad peaks at ∼655, 563, and 543nm. Cr doping is accompanied by an additional absorption in the whole visible region, increasing towards the band edge and the appearance of strongly pronounced inhomogeneously broadened near IR emission line peaking at 7780Å for T=10K. The shape of this line contains at least two well pronounced components A1 at 7780Å, A2 at 7740Å, and a weakly pronounced component A′1 at 7764Å, which are attributed to R1 and R2 emission lines (2E→4A2) of octahedral Cr3+ without local charge compensation (A1 and A′1) and to another 2E→4A2transition with broad unresolved R′1 and R′2 lines (A2) belonging to another Cr3+ centre with charge compensation defect. Details of photoluminescence observed are considered in comparison with analogous data for Cr-doped BaTiO3.

Evaluation of electro-optic, elasto-optic, piezoelectric, and elastic coefficients of Ba0.77Ca0.23TiO3 through orientation dependent photorefractive beam coupling

We present a demonstration of the influence of the indirect electro-optic effect on the photorefractive performance of Ba0.77Ca0.23TiO3 (BCT). The comparison of the orientation dependence of the two-beam coupling energy transfer gain with theoretical model allows us to obtain information on the electro-optic coefficients, but also an evaluation of the unknown elasto-optic, piezoelectric, and elastic stiffness coefficients of BCT. We found r13T=33 pm V−1 and r33T=170 pm V−1. These values are in good agreement with other published values. For the interesting coefficient r42T, we find a higher value r42T=465 pm V−1 than the one previously published. From this study we also determine that as in the case of BaTiO3, the optimal orientation is given by a 45°-cut BCT.

Experimental estimation of the bulk electric field and the photoconductivity of a Ba0.77Ca0.23TiO3 crystal (BCT)

Ba0.77Ca0.23TiO3 (BCT) crystals have interesting photorefractive and electrooptic properties, as was recently demonstrated in several papers. Analysing these results and our own experiments, we have come to the conclusion that there is an effective bulk electric field inside the crystal. In order to estimate the value of the suggested field inside the crystal we have developed an experimental method based on two-and four-wave mixing presented in this paper, where we use a BCT crystal grown by Kuper and co-workers from the University of Osnabruck. Knowing the value of the bulk field we have estimated the value of the effective photoconductivity of the crystal.

Light-induced charge-transport properties of photorefractive barium-calcium-titanate crystals doped with rhodium

Nominally pure and rhodium-doped barium-calcium-titanate crystals of the congruently melting composition Ba0.77Ca0.23TiO3 (BCT) are grown by the Czochralski technique. These crystals are characterized by holographic and conventional electrical experiments. The doped samples have an absorption maximum at 630 nm. They are hole conductive, and for intensities between 0.1 and 1 W cm-2 all properties are explained within a one-center charge-transport model. Two-beam-coupling gain factors up to 8 cm-1 are obtained, and doping with rhodium increases the effective trap density. Although diffusion is the dominant charge-driving force, bulk photovoltaic currents also occur which are especially pronounced in the range between 460 and 640 nm.