Excess Bi Research Articles

Structure, ferroelectric and dielectric properties of Bi2WO6 with different bismuth content

This paper reports that the Bi2WO6 ferroelectric ceramics with excess Bi2O3 of 0.0, 2.0, 3.5 and 5.0wt.% of the stoichiometric composition are prepared by the conventional solid-state reaction method. Their microstructure, ferroelectric properties, the concentration and mobility of the defects have been analysed systematically. With increasing Bi content, the remnant polarization decreases, and the broken-down voltage increases. The optimum Bi excess, 3.5, lowers the oxygen vacancy concentration, while further Bi-addition brings about more defects. The activation energies fitted from cole-cole plots are 0.97 eV, 1.07 eV, 1.18 eV, and 1.33 eV, respectively. This suggests that the mobility of the defects is weakened by Bi-addition, which may be due to the increase of the ratio of the number of Bi2O2 layers to that of the perovskite blocks.

Synthesis of bismuth and antimony complexes of the “larger” calix[n]arenes (n = 6–8); from mononuclear to tetranuclear complexes

A series of calix[n]arene (n=6-8) bismuth and antimony complexes were synthesized and fully characterized by NMR, X-ray, IR, UV-Vis and elemental analysis. The monobismuth calix[6]arene complex [Bi{tBuC6(H)3}]2 1 was prepared by the reaction of para-tert-butylcalix[6]arene (tBuC6(H)6) with one equivalent of Bi[N(SiMe3)2]3. Complex 1 featured a Bi2(micro-O)2 central core similar to other bismuth calixarene complexes prepared by our group. Reaction of calix[6]arene (HC6(H)6) with two equivalents of Bi(OtBu)3 yielded different outcomes depending on the reaction solvent. If THF was used, complex [Bi{HC6(H)3}] 2 was obtained in 72% yield; however, when toluene was used, complexes 2 and [Bi2{HC6}] 3 were isolated in 23 and 57% yields, respectively. Mononuclear complexes 1 and 2 displayed dimeric structures in the solid state with cone-like conformations for the calixarene ligands. The 1H NMR spectrum of complex 2 displays patterns for an asymmetric structure with two signals in a 2:1 ratio for the unreacted OH groups. Treatment of calix[6]arenes RC6(H)6 (R=H, tBu) with two equivalents of SbR3 (R=OtBu, NMe2) produced dinuclear complexes [Sb2{HC6}] 4, and [Sb2{tBuC6}] 5, respectively. The 1H NMR spectra for the dinuclear complexes 3, 4, and 5 showed the characteristic calixarene pattern for a 1,2,3-alternate conformer. In the process of recrystallization of complex 4 an unexpected trimetallic complex with composition [Sb3O2{HC6(H)}] 4a was obtained in low yield. Treatment of para-tert-butylcalix[7]arene (tBuC7(H)7) with two equivalents of Bi(OtBu)3 produced the bimetallic complex [Bi2O{tBuC7(H)3}]2 6. Complex 6 contains an overall Bi4O2(OAr)8 core system with a structural resemblance to other bimetallic bismuth calixarene complexes reported by our group. The larger para-benzylcalix[8]arene (BnC8(H)8) and calix[8]arene (HC8(H)8) reacted with excess Bi(OtBu)3 to produce the tetranuclear complexes [Bi4O2{HC8}] 7 and [Bi4O2{BnC8}] 8, respectively. The solid state structure of complex 8 featured a dimeric unit with the calixarene ligands in pinched-cone conformation and displaying an overall Bi8O4(OAr)16.H2O core. No metal pi-arene interactions were observed.

Synthesis, X-ray structures and reactivity of calix[5]arene bismuth(iii) and antimony(iii) complexes

A series of calix[5]arene bismuth(III) and antimony(III) mono- and bimetallic complexes were synthesized and fully characterized by NMR, X-ray, IR, mp, UV-Vis and elemental analysis. Reaction of p-tert-butylcalix[5]arene (tBuC5(H)5) trianionic salts M'3.tBuC5(H)2 (M'=Li, Na, K) with MCl3 (M=Bi, Sb) yielded monometallic complexes [Bi{tBuC5(H)2}] 1 and [Sb{tBuC5(H)2}] 2, respectively. 1H NMR spectra of both complexes showed two remaining OH groups available for further reactivity. Alternatively, complexes 1 and 2 can be obtained by reacting tBuC5(H)5 in a 1:1 ratio with M(OtBu)3, but the yields are lower. When the tBuC5(H)5 lower rim monobenzyl ether [tBuC5(Bn)(H)4] is treated in a 1:1 ratio with Bi(OtBu)3, the monometallic complex [Bi{tBuC5(Bn)(H)}]2 3 is prepared. If, however, [tBuC5(Bn)(H)4] reacts with Sb(NMe2)3 or Sb(OtBu)3 in a 1:2 ratio the production of the bimetallic complex [Sb2O{tBuC5(Bn)}] 4 is observed. p-Benzylcalix[5]arene (BnC5(H)5) reacts with excess Bi(OtBu)3 to produce the bimetallic complex [Bi2O{BnC5(H)}]2 5. 1H NMR spectra of 5 display patterns characteristic for a cone conformer in solution. Treatment of calix[5]arene [HC5(H)5] with one equivalent of Bi[N(SiMe3)2]3 or with 0.75 equivalents of Sb(NMe2)3 yields bimetallic complexes [Bi2O{HC5(H)}] 6 and [Sb2O{HC5(H)}] 7, respectively. The reactivity of monometallic complexes 1 and 2 was tested in order to investigate the availability of their remaining OH groups. Treatment of 1 with Bi(OtBu)3 at ambient temperature yields bimetallic complex [Bi2O{tBuC5(H)}]2 8 while the reaction of complex 2 with Sb(OtBu)3 in a 1:1 ratio produces complex [Sb2O{tBuC5(H)}] 9. The crystal structures of the monometallic bismuth complexes 1 and 3 display dimeric units with the calixarene ligands in distorted cone and "paco-in" conformations, respectively. Complexes 4, 7 and 9 are all monomeric units, displaying [(RO)2Sb]2(micro-O) cores and the calixarene ligands in 1,2-alternate conformation. The dimeric units of bimetallic complexes 5 and 8 contain Bi4O2(OR)8 core structures that force the calixarene ligands to adopt a flattened cone conformation.

Microstructure–Property Relationships in Liquid Phase‐Sintered High‐Temperature Bismuth Scandium Oxide‐Lead Titanate Piezoceramics

High‐temperature piezoelectrics are necessary for aeronautic and aerospace applications. The principal challenge for the insertion of piezoelectric materials is their limitation for upper use temperature, which is due to low Curie temperature and increasing conductivity at high temperatures. We investigated processing, microstructure, and property relationships of (1−x)BiScO3−(x)PbTiO3 composition as a promising high‐temperature piezoelectric. The effects of excess PbO and Bi2O3 and their partitioning in grain boundaries were studied using impedance spectroscopy, ferroelectric, and piezoelectric measurement techniques. Excess Pb addition increased the grain‐boundary conduction and the grain‐boundary area resulting in ceramics with higher AC‐conductivity (tan δ=0.9 and 1.7 for 0 and 5 at.% excess Pb at 350°C and at 10 kHz) that were not resistive enough to pole. Excess Bi addition increased the resistivity (tan δ=0.9 and 0.1 for 0 and 5 at.% excess Pb at 350°C and at 10 kHz), improved poling, and increased the piezoelectric coefficient from 354 to 408 pC/N for 5 at.% excess Bi addition. Thus, excess Bi2O3 proved to be a successful liquid phase forming additive to improve the 0.37BiScO3–0.63PbTiO3 piezoceramics for high‐temperature applications, as a result of increased resistivity and enhanced piezoelectric activity.

Compositional Analysis of Electrodeposited Bismuth Telluride Thermoelectric Thin Films Using Combined Electrochemical Quartz Crystal Microgravimetry−Stripping Voltammetry

Bismuth telluride (Bi 2Te 3 ) is a benchmark material for thermoelectric power generation and cooling applications. Electrodeposition is a versatile technique for preparing thin films of this material; however, it affords films of variable composition depending on the preparation history. A simple and rapid assay of electrodeposited films, therefore, has both fundamental and practical importance. In this study, a new protocol for the electroanalysis of Bi 2Te 3 thin films is presented by combining the two powerful and complementary techniques of electrochemical quartz crystal microgravimetry (EQCM) and stripping voltammetry. First, any free (and excess) tellurium in the electrodeposited film was reduced to soluble Te ( 2- ) species by scanning to negative potentials in a 0.1 M Na 2SO 4 electrolyte, and the accompanying frequency increase (mass loss) was used to determine the content of free tellurium. The film was again subjected to cathodic stripping in the same medium (to generate Bi (0) and soluble Te (2-) from the Bi 2 Te 3 film component of interest), and the EQCM frequency change was used to determine the content of chemically bound Te in the Bi 2Te 3 thin film and thereby the compound stoichiometry. Finally, the EQCM frequency change during Bi oxidation to Bi (3+) and the difference between total Bi and Bi in Bi 2Te 3 resulted in the assay of free (excess) Bi in the electrodeposited film. Problems associated with the chemical/electrochemical stability of the free Bi species were circumvented by a flow electroanalysis approach. Data are also presented on the sensitivity of electrodeposited Bi 2Te 3 film composition to the electrodeposition potential. This newly developed method can be used for the compositional analysis of other thermoelectric thin-film material candidates in general.

Effect of bismuth excess on ferroelectric and piezoelectric properties of a (Na0.5Bi0.5)TiO3–BaTiO3 composition near the morphotropic phase boundary

(Na0.5Bix)0.93Ba0.07TiO3 (x = 0.500–0.510) ceramics were prepared by a citrate method and the structure and electrical properties of the ceramics were investigated. No significant change in both phase structure and microstructure with the Bi excess was found. A significant influence of the Bi excess on the ferroelectric and piezoelectric properties was detected at relative high excess Bi amounts. The variation of the electrical properties with excess Bi amount was rather slight when x ≤ 0.504, the specimens within this composition range exhibited large remanent polarizations (Pr) of 37.5–41.1 μC/cm2 at room temperature, a constant depolarization temperature (Td) of 85 °C and high piezoelectric constants (d33) of 171–176 pC/N. Higher excess Bi amounts (x ≥ 0.505) resulted in a considerable degradation of the ferroelectricity, a decrease of the depolarization temperature and a remarkable decline of the piezoelectricity. The variation of the electrical properties with excess Bi amount was qualitatively explained with respect to the formation of A-site vacancies originating from incorporation of the excess Bi into the perovskite structure.

Piezoelectric and ferroelectric properties of Bi-compensated (Bi1/2Na1/2)TiO3–(Bi1/2K1/2)TiO3 lead-free piezoelectric ceramics

( Bi 1 / 2 Na 1 / 2 ) TiO 3 – ( Bi 1 / 2 K 1 / 2 ) TiO 3 (BNT-BKT) ceramics as a promising candidate for lead-free piezoelectric ceramics were studied with a special emphasis on the compositional dependence of piezoelectric and ferroelectric properties. One mole percent excess Bi was added to compensate for the volatilization of Bi3+ ions during sintering, which was found to be effective in improving the piezoelectric properties of the resultant BNT-BKT ceramics. The piezoelectric, ferroelectric, and dielectric properties of the Bi-compensated BNT-BKT ceramics were investigated and discussed in relation to the morphotropic phase boundary that is close to the composition range of 20–24 mol % BKT. The maximum piezoelectric constant d33 (207 pC/N) and electromechanical coupling factor kp (35%) were obtained at the compositions of 23% and 20%, respectively.

CaBi4Ti4O15 thin film deposition on electroplated Platinum substrates using a sol-gel method

ABSTRACTCaBi4Ti4O15 growth on different Platinum substrates was carried out through a sol-gel method. Higher crystallization temperature and 20% excess Bi decreased pyrochlore contents in the CaBi4Ti4O15 films. Repetition through coating, calcination and crystallization decreased void formation on the surface. C-axis oriented thin film could be grown on sputtered platinum substrates with low Pt (200) orientation. On electroplated Pt substrates, (119) oriented CaBi4Ti4O15 thin film was grown, suggesting surface roughness of Pt substrates is a crucial factor for orientation control of sol-gel derived CaBi4Ti4O15 thin film.

Effect of excess Bi 2O 3 on the ferroelectric and dielectric properties of Bi 3.25La 0.75Ti 3O 12 thin films by RF sputtering method

Bi 3.25La 0.75Ti 3O 12 (BLT) thin films derived from different amounts of Bi 2O 3 excess content were fabricated on Pt/TiO 2/SiO 2/Si using RF-magnetron sputtering method. The effect of Bi 2O 3 excess content on the microstructure, ferroelectric and dielectric properties of the BLT films was investigated. The X-ray diffraction analysis reveals a layered perovskite structure phase without pyrochlore phase for all the BLT films. Appropriate amount of excess bismuth improves remnant polarization of the BLT film, while too much excess bismuth leads to a reduction in remnant polarization and an increase in coercive voltage. P– V loops of well-established squareness were observed for the BLT films derived from a moderate amount of Bi 2O 3 excess (7.5 mol%), where a remnant polarization (2Pr) of 25.26 μC/cm 2 and coercive voltage (Vc) of 3.62 V were shown. A similar change in dielectric constant with the increasing of Bi 2O 3 excess content was also observed. Moreover, the BLT thin film derived from 7.5 mol% Bi 2O 3 excess shows the best fatigue resistance characteristics and about 8.1% polarization degradation after 1 × 10 9 read/write switching cycles.

BI CONCENTRATION DEPENDENCE OF STRUCTURAL, FERROELECTRIC AND MAGNETIC PROPERTIES OF BiFeO3FILMS

ABSTRACT Bi-rich BiFeO3 films were fabricated by chemical solution deposition followed by a post-deposition annealing at 823 K in air. Not only the polycrystalline BiFeO3 phase but also the bismuth oxide phases were formed at high excess Bi contents. This suggested that the Bi atoms were not significantly evaporated. The remanent polarization decreased as the excess Bi contents increased at 90 K, though the remanent polarization of 33 μ C/cm2 was still obtained at the excess Bi contents of 30 at.%. The magnetization monotonically decreased as the excess Bi content increased. It could be considered that the optimal Bi content is the stoichiometric value of BiFeO3 in the preparing way of the CSD followed by the annealing at 823 K.

Embedded polytypes inBi2Sr2−xLaxCuO6thin films grown by laser ablation

We investigate the presence of secondary phases in La-doped Bi-2201 thin films grown by laser ablation. The cation ratios in the target material, the oxygen pressure, and the substrate temperature during the deposition are the main parameters determining the presence of diluted intergrowth and/or polytype aggregates. A statistical model of random intergrowth is used to analyze the x-ray diffraction (XRD) anomalies caused by hidden defects and to characterize the latter. A detailed structural XRD refinement on oriented aggregates allows us to identify the guest phase as a Bi deficient phase, Bi-1201. The occurrence of this particular embedded polytype is accompanied by a global Bi deficiency introduced in the films by the growing process and/or by the annealing treatment. The presence of La favors the Bi-1201 formation mostly as La-rich $c$-axis oriented aggregates. Bi excess in the target material improves considerably the crystallographic structure of Bi-2201, avoids intergrowth formation, but does not prevent the phase separation of Bi-1201 in La-doped thin films. We also investigate the influence of the deposition parameters on the type of intergrowth as well as their variation with La doping. This work introduces a specific methodology for optimizing the growth of thin films grown by laser ablation, which applies to layered oxides that admit polytypes with close formation enthalpies in their phase diagram.

The influence of different fabrication processes on characteristics of excess Bi 2O 3-doped 0.95 (Na 0.5Bi 0.5)TiO 3–0.05 BaTiO 3 ceramics

In this study, we will develop the influences of the excess x wt% ( x=0, 1, 2, and 3) Bi 2O 3-doped and the different fabricating process on the sintering and dielectric characteristics of 0.95 (Na 0.5Bi 0.5)TiO 3–0.05 BaTiO 3 ferroelectric ceramics with the aid of SEM and X-ray diffraction patterns, and dielectric–temperature curves. The 0.95 (Na 0.5Bi 0.5)TiO 3–0.05 BaTiO 3+ x wt% Bi 2O 3 ceramics are fabricated by two different processes. The first process is that (Na 0.5Bi 0.5)TiO 3 composition is calcined at 850 °C and BaTiO 3 composition is calcined at 1100 °C, then the calcined (Na 0.5Bi 0.5)TiO 3 and BaTiO 3 powders are mixed in according to 0.95 (Na 0.5Bi 0.5)TiO 3–0.05 BaTiO 3+ x wt% Bi 2O 3 compositions. The second process is that the raw materials are mixed in accordance to the 0.95 (Na 0.5Bi 0.5)TiO 3–0.05 BaTiO 3+ x wt% Bi 2O 3 compositions and then calcining at 900 °C. The sintering process is carried out in air for 2 h from 1120 to 1240 °C. After sintering, the effects of process parameters on the dielectric characteristics will be developed by the dielectric–temperature curves. Dielectric–temperature properties are also investigated at the temperatures of 30–350 °C and at the frequencies of 10 kHz–1 MHz.

Thin films in ternary Bi–Mn–O system obtained by pulsed laser deposition

We have explored the influence of deposition temperature and the deposition rate on the growth of the ternary Bi–Mn–O system onto (0 0 1) SrTiO 3 substrates by pulsed laser deposition. The studies were performed with a fixed oxygen pressure of 10 Pa (0.1 mbar) and substrate temperatures between 600 and 680 °C. The films were obtained from non-stoichiometric targets with 10 and 15% Bi excess in order to compensate for Bi volatility. The fact that the compound is metastable together with the high volatility of Bi induces different Bi and Mn oxides apart from BiMnO 3. Stabilisation of epitaxial BiMnO 3 is therefore very elusive and only in a narrow temperature window around 630 °C the presence of spurious phases is reduced to traces. X-ray diffraction results reveal a correlation between the Bi–Mn–O compounds and the deposition temperature. Reciprocal space maps show that the BiMnO 3 grows completely strained on SrTiO 3 substrates. The unit cell has a reduced volume, which could be due to the presence of Bi vacancies. The surface of the films is rough, but they flatten when the films are obtained at lower deposition rates.

Effects of Excess Bismuth Content in Precursor Solutions on Ferroelectric Properties of BiFeO3 Thin Films Prepared by a Chemical Solution Deposition

Cr-substituted BiFeO3 (BFCr) thin films prepared from precursor solutions with stoichiometric composition and various excess Bi contents ranged from 5 to 20 mol% were fabricated on Pt/TiO2/SiO2/Si(100) substrates by a chemical solution deposition method, and the effects of excess Bi content in precursor solutions on the ferroelectric properties of the as-deposited BFCr thin films were studied. It was found that the BFCr thin film prepared from precursor solution with excess Bi content of 5 mol% exhibited the best dielectric constant–frequency and polarization–electric field characteristics. In detail, its dielectric constant is 158 at frequency of 100 kHz and remnant polarization (P r ) value is 49 μ C/cm2 at electric field of 600 kV/cm.

Deposition of bismuth-titanate films with liquid-delivery spin MO-CVD

A vertical liquid-delivery metal-organic chemical vapour deposition (MO-CVD) reactor was used to deposit Bi 4Ti 3O 12 films on SrTiO 3(1 0 0) substrates. Depending on the growth conditions the films show a pure Bi 4Ti 3O 12 phase or additionally a Bi poor phase. Well-ordered, (0 0 1)-oriented, epitaxially grown Bi 4Ti 3O 12 films were obtained at a growth temperature of 700 °C, a Bi excess of 25%, and a substrate rotation between 500 and 750 rpm. The Bi deficiency can be influenced by the concentration of MO precursor in the liquid solution. Depositions on NdGaO 3(1 1 0) also result in epitaxial (0 0 1)-oriented Bi 4Ti 3O 12 films, but the structural quality was slightly poorer.

Improved characteristics of Bi 4Ti 3O 12 thin film on ITO glass by using excess Bi 2O 3-added Bi 4Ti 3O 12 ceramic as source target

Bi 4Ti 3O 12 thin films are deposited on ITO/glass substrates by RF magnetron sputtering at room temperature using ceramic targets of Bi 4Ti 3O 12+4 wt% Bi 2O 3 and Bi 4Ti 3O 12, respectively. Thin films of thickness 600–700 nm are deposited and then annealed using rapid thermal annealing (RTA) technique conducted in an oxygen atmosphere at temperatures ranging from 625 to 725 °C with a heating rate of 900 °C/min. XRD analysis reveals that the crystallization temperature of the films deposited using the Bi 4Ti 3O 12+4 wt% Bi 2O 3 target is 25 °C lower than that of films deposited using Bi 4Ti 3O 12 target. Moreover, the crystallinity of the former films is superior to that of the latter under the same fabrication conditions. The EDS results indicate that the Bi/Ti atomic ratio decreases with an increasing annealing temperature, which suggests that evaporation loss of the bismuth occurs during the heating process. The relative dielectric constant and the polarization charge density of the films deposited using the Bi 4Ti 3O 12+4 wt% Bi 2O 3 target are found to be 295 and 12 μC/cm 2, respectively, which are approximately 70% and 25% higher than the respective values of the films deposited using the stoichiometric Bi 4Ti 3O 12 target. Although the leakage current density of the former films is somewhat higher than that of the latter, it is more stable and remains constant at approximately 1×10 −5 A/cm 2 under 360 kV/cm without breakdown.

Effects of Excess Bismuth on Structure and Properties of SrBi 4 Ti 4 O 15 Ceramics

SrBi 4Ti 4O 15(SBTi) ferroelectric ceramics with excess bismuth (Bi) contents ranging from 0% to 25% were prepared by sol-gel method. Effects of excess Bi contents on the microstructure and electric properties were investigated. The SBTi ceramics sample with 10% of excess Bi showed a pure layered perovskite structure with enhancee electric properties. Its Curie temperature, relative dielectric constant, dielectric loss, remanent polarization (2Pr) and coercive field (2Ec) were 518 °C, 248, 0.0021, 20.5 μC·cm −2and 87.8 kV · cm −1, respectively. The degraded electric properties observed in SBTi ceramics with excess bismuth contents lower or higher than 10% could be attributed to the structure defects and the formation of a second phase.

80 K superconductivity in Bi-2201 phase

We report 80K superconductivity observed for the crystals of Bi2+xCaySr2−x−y−zLazCuO6+δ with varying Ca-content y (0≦y≦2−x−z) under various values of excess Bi (0≦x≦0.2) and La (0≦z≦0.4) doping. Powder X-ray diffraction patterns and transmission electron microscope images indicate the crystals of Bi-2201 phase with orthorhombic structure. Temperature dependence of magnetic moment exhibits bulk superconductivity with the transition temperature of 77–87K, while the volume of the superconductivity changes with Ca-content. Those results suggest a model of inhomogeneous distribution of 80K superconductivity with Ca-substitution for Sr.

The crystal structures and dielectric properties of Bi 2O 3 doped SrBi 2Ta 2O 9 ceramics

Ferroelectric materials with Bi-layered structure such as SrBi 2Ta 2O 9 composition with excess x wt.% Bi 2O 3 ( x = 0, 2, and 4) are investigated as the main composition, the effect of excess Bi 2O 3 content and sintering temperatures on the crystal structure and dielectric characteristics of SrBi 2Ta 2O 9 ceramics are developed. Even 1280 °C is used as the sintering temperature of stoichiometry SrBi 2Ta 2O 9 composition, the X-ray diffraction patterns will show that the SrBi 2Ta 2O 9 phase is coexisted with the raw material of Ta 2O 5 and the secondary phases of SrBi 2O 4 and BiTaO 4. For SrBi 2Ta 2O 9 composition with excess 2 wt.%- or 4 wt.%-Bi 2O 3-doped and sintered at 1040 °C, the Ta 2O 5, SrBi 2O 4, and BiTaO 4 phases are eliminated and only the SrBi 2Ta 2O 9 phase is observed in the X-ray diffraction patterns. It is found that sintering temperatures and excess Bi 2O 3 content have large influence on the grain growth, the bulk densities, the maximum dielectric constants, and the Curie temperatures of SrBi 2Ta 2O 9-based ceramics.

Effect of trivalent ions (La 3+, Nd 3+) on the properties of Bi 4Ti 3O 12 single crystals

Growth of trivalent ions (La 3+ and Nd 3+) doped Bi 4Ti 3O 12 (BIT) single crystal by self-flux method using excess Bi 2O 3 as flux is reported. The effects of trivalent ions on the structural, thermal, optical and ferroelectric properties of BIT crystal were investigated. The results of X-ray diffraction and thermal analysis, respectively, indicate that the lattice distortion, liquidus/crystallization temperatures of BIT considerably increase with La and Nd concentrations. Substitution of La in Bi 3+ shifts the lower absorption edge towards the ultra-violet region (∼20–25 nm), while no shift is observed for the BIT:Nd crystal. Regardless of the dopants, the optical microscopy patterns of the crystal surfaces reveal the existence of 90° domains. Dielectric measurements indicate that BIT:Nd crystals exhibit no significant variation in Curie temperature ( T C) of BIT. Substitution of La and Nd in BIT increase both the remnant polarization ( P r) and coercive field ( E c) of BIT crystals.