Bismuth Layer-structured Ferroelectric Ceramics Research Articles

Electrical Properties of Textured Bismuth Layer-Structured Ferroelectric Ceramics with Large Number of Layers (m = 5)

Bismuth layer-structured ferroelectrics (BLSF) ceramics are attractive materials for high temperature sensor applications, because of their high Curie temperature Tc (300–900 °C), and the large anisotropy of their electromechanical coupling factor kt/kp or k33/k31. In this study, BLSF ceramics with a large number of layers, namely, (K0.5Bi0.5)2Bi4Ti5O18 + MnCO3 0.3 wt%+ Bi2O3 0.025 wt% (KBT5) and Sr0.75Ca0.25Na0.5Bi4.5Ti5O18 + CeO2 1 wt% [(SC)NBT5] ceramics, were prepared by ordinary firing (OF) and hot forging (HF) methods, and their electrical and piezoelectric properties were examined. Both KBT5 and (SC) NBT5 ceramics showed high Tc values of 545 and 424 °C, respectively. The OF-KBT5 ceramic had an electromechanical coupling factor k33 of 0.14 and a piezoelectric constant d33 of 20 pC/N, whereas the HF-KBT5 ceramic had k33 of 0.17 and d33 of 31 pC/N. On the other hand, the OF-(SC) NBT5 ceramic had k33 of 0.13 and d33 of 17 pC/N, whereas the HF-(SC) NBT5 ceramic had k33 that increased to 0.32 and d33 to 41 pC/N. The k33 and d33 of the HF ceramics were improved compared with those of the OF ceramics. Thus, the KBT5 and (SC) NBT5 ceramics with oriented grains were shown to have good piezoelectric properties with high Tc.

Textured Bi4Ti3O12 Ceramics: One‐Step Spark Plasma Sintering and Their Single‐Crystal‐Like Polar Anisotropy

Texturing is the most effective way to engineer the performance of bismuth layer–structured ferroelectric (BLSF) ceramics by utilizing the strong anisotropy of grains, but the existing processing approaches are still complex. Herein, a one‐step spark plasma sintering (SPS) approach is demonstrated to prepare textured Bi4Ti3O12 (BiT) ceramics with high performance. The degree of orientation can be controlled from 57% to 95% by only adjusting the sintering temperature from 840 to 1000 °C. The largest spontaneous polarization (Ps) of ≈32.2 μC cm−2 is obtained in 95% <001> textured ceramics along the direction perpendicular to the SPS pressure, accompanied with the maximum electro‐strain of ≈0.14% and piezoelectric coefficient of 14.3 pC N−1. Moreover, under the same conditions of poling and illumination, the textured ceramics exhibit unique anisotropic photoresponse in which the photocurrent polarity is dependent on the testing orientations. In particular, a short‐circuit photocurrent density of 8.76 nA cm−2 is achieved along the direction of SPS pressure after positive poling, while the value goes to −79.4 nA cm−2 along direction perpendicular to the SPS pressure. These results are expected to provide a paradigm to achieve highly textured BLSF ceramics for electric and photoelectric applications.

Effect of tantalum substitution on the structural and electrical properties of BaBi8Ti7O27 intergrowth ceramics

In this work, BaBi8(Ti1-xTax)7O27 (x = 0, 0.005, 0.01, 0.015, 0.02 and 0.03) intergrowth bismuth layer-structured ferroelectric ceramics (BLSFs) were prepared by traditional solid reaction method, and Ta5+ was designed to replace Ti4+ to regulate crystal structure and improve electrical properties. The results show that Ta5+ as a donor increases an orthogonal distortion, while reducing the concentration of oxygen vacancies in the ceramics.The results show that the structural distortion increases with Ta doping due to the larger radius of the Ta ion compared to that of the Ti ion. At the same time, proper Ta5+ doping as a donor can effectively inhibit the formation of oxygen vacancies, which reduces high temperature leakage, and can cause a sharp reduction of grain size. However, excessive Ta5+ doping also results in a serious structural distortion, and consequently a serious deterioration of electrical properties. BaBi8(Ti0.995Ta0.005)7O27 shows an optimal piezoelectric performance with a piezoelectric constant d33 of 19 pC/N, which is twice as large as that of pure BaBi8Ti7O27 (~8 pC/N), and verifies its possibility as a potential candidate material for high temperature piezoelectric field.

Cerium induced larger lattice distortion and piezoelectric properties of Aurivillius oxide Na0.25K0.25Bi2.5Nb2O9

Bismuth layer-structured ferroelectric ceramics, K0.25Na0.25Bi2.5Nb2O9 (KNBN) with the cerium addition, were synthesized by using a solid-state reaction process. It is desirable that spontaneous polarization in the a-b plane and resistivity of the KNBN ceramic could be improved by means of bismuth cation vacancies compensated by the cerium addition. Phase structure of the cerium modified KNBN ceramics were confirmed to be a two-layer Aurivillius oxide with an orthorhombic space group A21am. Piezoelectric performances of the cerium modified KNBN ceramics were improved significantly compared with that of the KNBN ceramic. The maximum of piezoelectric coefficient (d33) was found to be 28 pC/N for the KNBN-Ce0.2 ceramic, together with high Curie temperature (Tc∼580 °C) and good temperature stability of piezoelectric properties.

Gamma-ray irradiation effects on electrical properties of bismuth layer-structured ferroelectric ceramics

Abstract In this study, we prepared the bismuth layer-structured ferroelectric (BLSF)-type Bi 4 Ti 3 O 12 (BiT), Bi 3.25 La 0.75 Ti 3 O 12 (BLaT), and Bi 3.1 Nd 0.9 Ti 3 O 12 (BNdT) ceramics using the solid-state reaction method. The prepared ceramics were irradiated at room temperature by using a 60 Co gamma-ray source in a dose range of 0–3000 kGy with a dose rate of 10 kGy/h to compare the structure and electrical properties of the irradiated ceramics. The X-ray diffraction analysis shows that the BLSF structure was well formed in all ceramics without a secondary phase. There was no structural change such as grain size change and secondary phase formation despite the cumulative gamma-ray dose of 3000 kGy. A comparison of the electrical properties with gamma-ray irradiation shows that the BiT ceramics exhibits a larger reduction ratio compared to the BLaT and BNdT ceramics. The rate of change of the remnant polarization (2 P r ) value with the gamma-ray irradiation doses was − 14.2%, − 8%, and − 3.4% in BiT, BLaT, and BNdT ceramics, respectively, at a cumulative gamma-ray dose of up to 3000 kGy. Furthermore, the dielectric relaxation phenomenon in BiT ceramics at low frequency was observed when gamma rays of 1000 kGy or more were irradiated. Based on these results, in this study, we investigated the structure and electrical properties of BLSF ceramics with gamma-ray irradiation.

Comparison between the electrical properties of bismuth layer-structured and intergrowth bismuth layer-structured ferroelectric ceramics

Bismuth layer-structured ferroelectric (BLSF)-type Bi4Ti3O12 (BiT), Bi3.25La0.75Ti3O12 (BLaT), and Bi3.1Nd0.9Ti3O12 (BNdT) ceramics and intergrowth BLSF-type BiT-CaBi4Ti4O15 (CBTO), BLaT-CBTO, and BNdT-CBTO ceramics were prepared using the solid-state reaction method. The electrical and the high-temperature properties of the intergrowth BLSF ceramics were compared with those of BLSF ceramics to investigate the possibility of using the former for high-temperature applications. The X-ray diffraction (XRD) analysis revealed well-formed stable structures in all BLSF and intergrowth BLSF ceramics without any second-phase formation. When their electrical properties were examined, the intergrowth BLSF ceramics BiT-CBTO, BLaT-CBTO, and BNdT-CBTO were found to outperform the BLSF ceramics BiT, BLaT, and BNdT, respectively, in terms of the remanent polarization and piezoelectric coefficient values. Among the intergrowth BLSF ceramics, those doped with rare-earth ions La and Nd, i.e., BLaT-CBTO and BNdT-CBTO ceramics, were found to have improved electrical properties compared to the BiT-CBTO ceramics. In particular, the dielectric constants and the piezoelectric coefficients of the BNdT-CBTO ceramics were observed to be as high as 146 and 15.4 pC/N, respectively, which were 28% and 10% higher than those of BNdT ceramics. In the thermal depoling behavior measured to examine high-temperature stability, the intergrowth BLSF ceramics, compared to the BLSF ceramics, demonstrated improvements in the thermal depoling temperature ranging from 100 to 300 °C.

Strong red emission and enhanced ferroelectric properties in (Pr, Ce)-modified Na0.5Bi4.5Ti4O15 multifunctional ceramics

Bismuth layer-structured ferroelectric (BLSFs) ceramics of Na0.5Bi4.5−x (Pr0.5Ce0.5) x Ti4O15 (NBT-x(Pr, Ce), x = 0.000, 0.004, 0.008, 0.012) were prepared by a conventional solid-state reaction method, and the influence of (Pr, Ce) additive on the ferroelectric, dielectric, and photoluminescence properties of samples were investigated. It is found that all the samples have a bismuth oxide layered structure with a dense microstructure. After (Pr, Ce) doping, the samples showed a bright red photoluminescence. The sharp excitation peaks around 449, 480 and 491 nm correspond to the 3H4 → 3P2, 3H4 → 3P1 and 3H4 → 3P0 transition, respectively. Upon the excitation of 492 nm light at room temperature, samples show two emission bands located at 611 and 656 nm, respectively. The strong red emission band centered at 611 nm is attributed to 1D2 → 3H4 transition, and the weak red emission located 656 nm is due to the 1D2 → 3H5 transition. In addition, it is an intrinsic ferroelectric and piezoelectric material, and the enhanced ferroelectric properties were obtained by (Pr, Ce) doping. At x = 0.004, the remnant polarization 2P r reaches 13.54 μC/cm2, together with a high Curie temperature (T c = 662 °C) and activation energy of E a = 0.83 eV. As a multifunctional material, the (Pr, Ce)-modified NBT piezoelectric ceramic may be useful in white LEDs, sensor and optical-electro integration.

Strong photoluminescence and good electrical properties in Eu-modified SrBi2Nb2O9 multifunctional ceramics

Bismuth layer-structured ferroelectric (BLSFs) ceramics of Sr1−xEux Bi2Nb2O9 (SBT-xEu, x=0.000, 0.002, 0.004, 0.006) were prepared by a conventional solid-state reaction method. All the samples have a bismuth oxide layered structure with a dense microstructure. The ferroelectric, piezoelectric, dielectric and optical properties of the ceramics were investigated. After Eu3+ doping, samples show a bright red photoluminescence upon blue light excitation of the 400–500nm. Upon the excitation of 465nm light, the materials have two intense emission bands peaking around 593nm (yellow) and 616nm (red). Meanwhile, good electrical properties with large piezoelectric constant d33 of 14pC/N and large remnant polarization 2Pr of 11.97μC/cm2 are obtained at x=0.006. Moreover, this material has a high Curie temperature (Tc=429°C) and high resistivity, which makes the material resistant to thermal depolarization up to its Curie temperature. This feature indicates that the SBN-xEu ceramics have a latent use in high temperature applications.

Bright upconversion emission and enhanced piezoelectric properties in Er-modified bismuth layer-structured SrCaBi4Ti5O18 ceramics

Bismuth layer-structured ferroelectric ceramics of SrCaBi4−x Er x Ti5O18 (SCBT-xEr, x = 0.00, 0.02, 0.04 and 0.06) were prepared by a conventional solid-state reaction method, and their ferroelectric, dielectric, piezoelectric and photoluminescence properties were investigated. The results indicated that all ceramics have a bismuth oxide layered with a dense structure. After Er3+ doping, samples show a bright up-conversion photoluminescence while simultaneously obtaining an enhanced ferroelectric and piezoelectric properties. A bright green (548 nm) and a weak red (681 nm) emission bands were obtained under excitation (980 nm) at room temperature, which correspond to the transitions from 4S3/2 to 4I15/2 and 4F9/2 to 4I15/2, respectively. Ferroelectric and piezoelectric measurements show that the Er3+-doped ceramics showed an increase in remnant polarization and piezoelectric constant. At x = 0.04, the piezoelectric constant d 33 reaches up to 13pC/N, together with a large remnant polarization (2P r = 16 μC/cm2) and high Curie temperature (T c = 573 °C). As a multifunctional material, Er3+-doped SCBT ferroelectric oxide showed great potential in optical electro integration and coupling device applications.

High performance Aurivillius type Na0.5Bi4.5Ti4O15 piezoelectric ceramics with neodymium and cerium modification

Bismuth layer-structured ferroelectric ceramics of Na0.5Bi4.5−x (Nd0.5Ce0.5) x Ti4O15 (NBT-x, 0.0 ⩽ x ⩽ 0.4) were synthesized by a traditional solid-state reaction. The effect of (Nd,Ce) substitution for A-site on the microstructure and electrical properties of Na0.5Bi4.5Ti4O15 (NBT)-based piezoelectric ceramics was investigated. X-ray diffraction (XRD) analysis revealed that the (Nd,Ce)-modified NBT ceramics have a pure four-layer Aurivillius type structure. The piezoelectric properties of NBT ceramics were significantly improved by the modification of neodymium and cerium. The Curie temperature T C gradually decreased from 638 °C to 618 °C with increasing the (Nd,Ce) modification. The piezoelectric constant d 33, mechanical quality factor Q m, dielectric loss tanδ and Curie temperature T C of the Na0.5Bi4.3(Nd0.5Ce0.5)0.2Ti4O15 ceramic were found to be 28 pC/N, 3239, 0.0032 and 630 °C, respectively. Thermal annealing studies indicated that the (Nd,Ce)-modified NBT ceramics possess stable piezoelectric properties, demonstrating that the Na0.5Bi4.3(Nd0.5Ce0.5)0.2Ti4O15 ceramic is a promising candidate for high temperature applications.

Microstructure and electrical properties of Mn-modified bismuth-layer Na0.25K0.25Bi2.5Nb2O9 Ceramics

Bismuth layer-structured ferroelectric ceramics Na0.25K0.25Bi2.5Nb2O9+xmol% MnCO3 (NKBN–Mn) were synthesized by a traditional solid-state reaction. The effects of Mn addition on the microstructure and electrical properties of ceramics have been investigated in details. It was found that the ceramics possess a pure phase of bismuth oxide layer-type structure. The Curie temperature Tc gradually decreases from 653 to 624°C with increasing the Mn modification. The electrical properties of NKBN-based ceramics are improved significantly by the addition of Mn. The piezoelectric constant d33, dielectric loss tan δ, mechanical quality factor Qm and remanent polarization Pr for the NKBN ceramics with 3.0mol% MnCO3 modification were found to be 25 pC/N, 0.28%, 2817, 14.50μC/cm2, respectively, together with the high Tc (∼643°C) and stable piezoelectric properties, demonstrating that the Mn modified NKBN-based ceramics are the promising candidates for high-temperature applications.

ビスマス層状構造強誘電体(Sr0.7Ca0.3)2Bi4Ti5O18セラミックスを用いた超音波モーターの作製と評価

ビスマス層状構造強誘電体(Sr0.7Ca0.3)2Bi4Ti5O18セラミックスを用いた超音波モーターの作製と評価

High-Power Piezoelectric Characteristics of Nontextured Bismuth Layer-Structured Ferroelectric Ceramics

High-power piezoelectric characteristics under continuous driving were studied on some bismuth layer-structured ferroelectric ceramics, i.e., Sr0.25Bi2.75Ti0.75Ta1.25O9 (SBTT, m = 2), Bi4Ti2.98V0.02O12 (BITV, m = 3), Bi4Ti3O12–SrBi4Ti4O15 + MnCO3 0.2 wt % (BIT–SBTi, m = 3, 4), and (Sr0.7Ca0.3)2Bi4Ti5O18 + MnCO3 0.2 wt % (SCBT, m = 5). The vibration velocities, v0–p, of SBTT, BIT–SBTi, and SCBT ceramics were above 2.0 m/s at 5 V/mm. Also, we observed that the resonance frequency changes and temperatures on the sample surfaces for SBTT, BIT–SBTi, and SCBT ceramics were less than 1.0% and 50 °C at a v0–p of 2.0 m/s, respectively. The high-power characteristics of the ceramics were superior to those of BITV and hard Pb(Zr,Ti)O3 (abbreviated as PZT) at a vibration velocity v0–p > 0.6 m/s. Therefore, SBTT, BIT–SBTi and SCBT ceramics are promising candidates for lead-free high-power applications requiring high vibration velocity and frequency stability.

High-Power Piezoelectric Characteristics of Nontextured Bismuth Layer-Structured Ferroelectric Ceramics

High-Power Piezoelectric Characteristics of Nontextured Bismuth Layer-Structured Ferroelectric Ceramics

反応制御焼結法を用いた Bi 層状構造強誘電体の作製

反応制御焼結法を用いた Bi 層状構造強誘電体の作製

Microstructure and Properties of High-Temperature Materials (1−x) Na0.5Bi2.5Nb2O9-xLiNbO3

Bismuth layer-structured ferroelectric ceramics of (1−x)Na0.5Bi2.5Nb2O9–xLiNbO3 (NBN–LN, 0≤x≤0.2) were synthesized by a traditional solid-state reaction. The effects of LN addition on the microstructure and electrical properties of ceramics were studied carefully. It was found that the ceramics with x≤0.10 have a bismuth oxide layered structure. With the increasing of LN addition, the mechanical quality factor Qm firstly increases, and then decreases with a maximum value of 4820 at x=0.02. The Curie temperature Tc increases gradually and the electrical properties of NBN-based ceramics are improved significantly by the addition of LN. The piezoelectric constant d33, dielectric loss tan δ, Curie temperature Tc, and remanent polarization Pr of 0.90Na0.5Bi2.5Nb2O9–0.10LiNbO3 ceramics were found to be 21 pC/N, 0.16%, 789°C, and 7.37 μC/cm2, respectively. Thermal annealing and aging studies indicate that the NBN–LN system possesses stable piezoelectric properties, demonstrating that the NBN–LN ceramics are the promising candidates for high-temperature applications.

Effect of point defects on thermal depoling behavior of bismuth layer-structured ferroelectric ceramics

Effect of point defects on the thermal depoling behavior of bismuth layer-structured ferroelectric Bi2WO6 (BW) and Sr2Bi4Ti5O18 (SBT) ceramics was investigated. Point defects in BW ceramics formed defect dipoles that interacted with the ferroelectric domain structure. These defect dipoles produced pinched polarization-electric field (P-E) hysteresis loops and an irreversible reduction in d33 after annealing below 200 °C. They became decoupled and randomized above 200 °C, and the d33 of BW became stable with increasing temperature from 200 °C up to its Curie point. SBT ceramics with low defect concentration showed symmetric P-E hysteresis loops and good piezoelectric stability with increasing temperature.

Characterization of the dielectric properties and alternating current conductivity of the SrBi5−xLaxTi4FeO18 (x=, 0.2) compound

Lanthanum-doped bismuth layer-structured ferroelectric ceramics SrBi5−xLaxTi4FeO18 (x=0,0.2) were prepared by the solid-state reaction method. X-ray diffraction patterns indicate that single phases were formed. Hysteresis loops at room temperature (20 °C) show that the La-doped ceramic presents a slightly lower spontaneous polarization than the undoped compound. Measurements of relative permittivity and dielectric loss versus temperature were performed from room temperature to 700 °C in the 100 Hz–1 MHz frequency range. Three anomalies were observed in the thermal behavior of the relative permittivity in both samples. Anomalies around the temperatures of 465 and 430 °C have been identified as the ferroelectric-paraelectric transition temperatures for the x=0 and 0.2 compounds, respectively. The sizable shift of the transition temperatures toward lower temperatures with the La doping is interpreted as a manifestation of the La ion incorporation into the crystal structure. From the conductivity studies, the activation energies as functions of frequency for three different temperature zones are obtained. It is found that activation energies are strongly frequency dependent, particularly in the low-frequency region. The frequency dependence of the conductivity at different temperatures was analyzed using Jonscher’s power law and the Almond-West conductivity formalism.

High-power piezoelectric characteristics of textured bismuth layer structured ferroelectric ceramics

Abstract-The high-power piezoelectric characteristics in h001i oriented ceramics of bismuth layer structured ferroelectrics (BLSF), SrBi(2)Nb(2)O(9) (SBN), (Bi,La)(4)Ti(3)O(12) (BLT), and CaBi(4)Ti(4)O(15) (CBT), were studied by a constant voltage driving method. These textured ceramics were fabricated by a templated grain growth (TGG) method, and their Lotgering factors were 95%, 97%, and 99%, respectively. The vibration velocities of the longitudinal mode (33-mode) increased proportionally to an applied electric field up to 2.5 m/s in these textured BLSF ceramics, although, the vibration velocity of the 33-mode was saturated at more than 1.0 m/s in the Pb(Mn,Nb)O(3)-PZT ceramics. The resonant frequencies were constant up to the vibration velocity of 2.5 m/s in the SBN and CBT textured ceramics; however, the resonant frequency decreased with increasing over the vibration velocity of 1.5 m/s in the BLT textured ceramics. The dissipation power density of the BLT was almost the same as that of the Pb(Mn,Nb)O(3)-PZT ceramics. However, the dissipation power densities of the SBN and CBT were lower than those of the BLT and Pb(Mn,Nb)O(3)-PZT ceramics. The textured SBN and CBT ceramics are good candidates for high-power piezoelectric applications.

Temperature dependence of piezoelectric properties for textured SBN ceramics

Temperature dependences of piezoelectric properties were studied for h001i textured ceramics of bismuth layer-structured ferroelectrics, SrBi(2)Nb(2)O(9) (SBN). The textured ceramics with varied orientation degrees were fabricated by templated, grain-growth method, and the temperature dependences of resonance frequency were estimated. Excellent temperature stability of resonance frequency was obtained for the 76% textured ceramics. The resonance frequency of the 76% textured specimens varied almost linearly over a wide temperature range. Therefore, the variation was slight, even in a high temperature region above 150 degrees C. Temperature stability of a quartz crystal oscillator is generally higher than that of a ceramic resonator around room temperature. The variation of resonance frequency for the 76% textured SrBi(2)Nb(2)O(9) was larger than that of oscillation frequency for a typical quartz oscillator below 150 degrees C also in this study. However, the variation of the textured SrBi(2)Nb(2)O(9) was smaller than that of the quartz oscillator over a wide temperature range from -50 to 250 degrees C. Therefore, textured SrBi(2)Nb(2)O(9) ceramics is a major candidate material for the resonators used within a wide temperature range.