Effect of calcium substitution on structural,dielectric, ferroelectric,piezoelectric, and energy storage properties of BaTiO3

The effect of calcium substitution on the structural, dielectric, ferroelectric, piezoelectric, and energy storage properties of BaTiO₃ (BT) ceramics has been investigated. XRD confirmed the phase formation of Barium Calcium Titanate (BCT), and structural Rietveld refinement was used to estimate the lattice parameters. It is evident from the SEM data that the average grain size decreases as calcium is added. At Curie temperature (110 °C), BCT 0.10 ceramic has a good dielectric constant of 15834 and a very low dielectric loss of 0.009. According to the ferroelectric and piezoelectric investigations, BCT 0.10 exhibits maximum spontaneous polarization with the highest piezoelectric charge coefficient of 100 pC/N. BCT 0.10 has a maximum energy storage density of 96.8 mJ/cm³ and a good energy storage efficiency of 53.9%, which is around three times that of pure BaTiO₃. These results suggest that the BCT ceramic has good potential for energy storage applications.     

Ferroid properties and domain structure of barium titanate

Distinctive features of domain formation in ferroelectric crystals are discussed theoretically for the example of ferroelectric BaTiO₃, taking into account ferroid properties of higher order. Inclusion of ferroid properties makes it possible to refine the details of the domain formation, and in particular to explain the possible existence of charged domain walls in ferroelectric crystals. Fiz. Tverd. Tela (St. Petersburg) 39, 1634–1635 (September 1997)     

0.90(Bi1/2Na1/2)TiO3–0.05(Bi1/2K1/2)TiO3– 0.05BaTiO3 transducer for ultrasonic wirebonding applications

Lead-free piezoelectric ceramic 0.90(Bi_1/2Na_1/2)TiO₃–0.05(Bi_1/2K_1/2)TiO₃–0.05BaTiO₃ (BNKBT-5) rings (OD=12.7 mm, ID=5.1 mm and 2.3-mm thick) were fabricated and characterized. Four ceramic rings were used as the driving element in an ultrasonic wirebonding transducer and the performance of the transducer was characterized. The lead-free transducer was found to have comparable voltage rise and fall times as a lead-based PZT transducer and has a relatively large vibration amplitude, thus showing that BNKBT-5 has the potential to be used in fabricating lead-free ultrasonic wirebonding transducers. PACS 77.22.Ej; 77.84.-s; 85.50.-n     

Propagation of nonequilibrium phonons in ferroelectric ceramics and single crystals

Phonon transport in ferroelectric ceramics and single crystals has been experimentally investigated. Our measurements indicate that, in the temperature range 1.7–3.8 K studied, the effective phonon diffusion coefficient behaves as D _eff∞T ⁻⁵ in ferroelectrics with a broadened phase transition. This experimental dependence is in accord with the presence of a plateau in the thermal conductivity of such materials. The scattering by domain walls in BaTiO₃ single crystals has been identified, and our results are in quantitative agreement with calculations. Zh. éksp. Teor. Fiz. 115, 624–631 (February 1999)     

Surface tension and Curie temperature in ferroelectric nanowires and nanodots

The effect of surface tension associated internal pressure on the Curie phase transition in ferroelectric nanowires and nanodots has been investigated using a modified Landau–Ginzburg–Devonshire phenomenological approach. Based on experimental data on the size- dependent phase transition in freely suspended single-crystalline ferroelectric nanocrystals, bulk surface tension coefficients for BaTiO₃ and PbTiO₃ have been determined to be of the order of 1–2 N/m. The present theoretical study reproduces the size dependence of the transition temperature experimentally acquired in individual BaTiO₃ single-crystalline nanowires. In the case of PbTiO₃ single-crystalline nanodots, however, in order to fit the theoretically calculated size-dependent ferroelectric transition with the experimental data, an effective surface tension coefficient has been introduced, which is size dependent and can be much higher than the bulk value. An erratum to this article can be found at     

Large piezoelectric effects in charged, heterogeneous fluoropolymer electrets

Large piezoelectric d₃₃ coefficients around 600 pC/N are found in corona-charged non-uniform electrets consisting of elastically “soft” (microporous polytetrafluoroethylene PTFE) and “stiff” (perfluorinated cyclobutene PFCB) polymer layers. The piezoelectric activity of the two-layer fluoropolymer stack exceeds the d₃₃ coefficient of the ferroelectric ceramic lead zirconate titanate (PZT) by more than a factor of two and that of the ferroelectric polymer polyvinylidene fluoride (PVDF) by a factor of 20. Soft piezoelectric materials may become interesting for a large number of sensor and transducer applications, in areas such as security systems, medical diagnostics, and nondestructive testing. Accepted: 9 November 1999 / Published online: 3 December 1999     

Microstructure,dielectric and piezoelectric properties of (K<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>)NbO<Subscript>3</Subscript>-Ba(Ti<Subscript>0.95</Subscript>Zr<Subscript>0.05</Subscript>)O<Subscript>3</Subscript> lead-free ceramics with CuO sintering aid

Using an ordinary ceramic fabrication technique, we fabricated lead-free (1-x)(K_0.5Na_0.5)NbO₃-xBa(Ti_0.95Zr_0.05)O₃ ceramics with CuO sintering aid . Ba(Ti_0.95Zr_0.05)O₃ diffuses into (K_0.5Na_0.5)NbO₃ to form a new solid solution. The ceramics with perovskite structure possess orthorhombic phase at x≤0.04 and become tetragonal phase at x≥0.06. Both the paraelectric cubic–ferroelectric tetragonal and the ferroelectric tetragonal–ferroelectric orthorhombic phase transition temperatures decrease with increasing the concentration of Ba(Ti_0.95Zr_0.05)O₃. The doping of CuO effectively promotes the densification of the ceramics. The coexistence of the orthorhombic and tetragonal phases at 0.04<x<0.06 and the improvement in sintering performances of the ceramics significantly enhance the piezoelectric and dielectric properties at room temperature. The ceramics with x=0.04–0.06 and y=0.75–1.50 possess excellent properties: d₃₃=119–185 pC/N, k_P=37–44%, k_t=35–49%, ε=341–1129, cosδ=0.7–4.4% and T_c=312–346 °C. PACS 77.65.-j; 77.84.Dy; 77.84.-s     

Preparation of fine-grain lead indium niobate ceramics with wolframite precursor method and resulting electrical properties

In this study, lead indium niobate (Pb(In_1/2Nb_1/2)O₃ or PIN) ceramics were prepared by a wolframite precursor method via a vibro-milling technique. Fine-grain ceramics were achieved with average grain size of 1–2 μm, indicating advantage of the vibro-milling technique used. The dielectric and ferroelectric properties were measured by means of an automated dielectric measurement set-up and a standardized ferroelectric tester, respectively. The dielectric properties of PIN ceramic were measured as functions of both temperature and frequency. The results indicated that the dielectric properties of the PIN ceramic were of relaxor ferroelectric behavior with temperature of dielectric maximum (T_m)∼53 °C and dielectric constant (ε_r)∼4300 (at 1 kHz). The P–E hysteresis loop measurements at various temperatures showed that the ferroelectric properties of the PIN ceramic changed from the paraelectric behavior at temperature above T_m to slim-loop type relaxor behavior at temperature slightly below T_m. Moreover, the P–E loop became more open at temperatures much lower than T_m. PACS 77.22.Ch; 77.84.Dy     

Phase transitions in solid solutions (1 ? x)BaTiO3-xBaMg1/3B2/3O3 (B = Nb, Ta)

The dielectric properties of ceramic samples of (1 − x)BaTiO₃-xBaMg_1/3Nb_2/3O₃ and (1 − x)BaTio₃-xBaMg_1/3Ta_2/3O₃ solid solutions (x = 0–0.25) are investigated in the frequency range from 10 Hz to 100 kHz at temperatures of 77–450 K. It is shown that the (x−T) phase diagrams of these solid solutions at x = 0.05 have a multiphase point at which the lines of all three phase transitions of BaTiO₃ converge. Original Russian Text ? V.G. Zalesskiĭ, V.V. Lemanov, E.P. Smirnova, A.V. Sotnikov, N. V. Zaĭtseva, 2007, published in Fizika Tverdogo Tela, 2007, Vol. 49, No. 1, pp. 108–112.     

Nanocrystalline oxide (Y2O3, Dy2O3, ZrO2, NiO) coatings on BaTiO3 submicron particles by precipitation

Nanocoatings (5–20 nm) of different compounds on fine BaTiO₃ particles were obtained by means of precipitation processes. Homogeneous and smooth shells of Y(OH)CO₃ and Dy(OH)CO₃ were grown from nitrate solutions in the presence of urea. An irregular coating consisting of zirconia nanoparticles was produced from zirconyl nitrate solution using ammonia as a precipitating agent after adsorption of a polymeric polyelectrolyte on the BaTiO₃ surface. Composite particles with a peculiar morphology were obtained by inducing heterogeneous nucleation and growth of Ni(OH)₂ lamellae on the BaTiO₃ surface. The different shells can be transformed in a nanocrystalline coating of the corresponding oxide (Y₂O₃, Dy₂O₃, ZrO₂, NiO) by calcination at moderate temperatures (400–700 °C). The overall results indicate that precipitation from solution represents a versatile process to grow a second-phase layer on the surface of BaTiO₃ particles. This approach can be used as an alternative to mechanical wet mixing for controlled doping of ferroelectric materials and for the fabrication of composite materials with specific geometry of the two-phase assembly.     

Piezoelectric/photoluminescence effects in rare-earth doped lead-free ceramics

In the present work, we report the environmentally-friendly multifunctional effects—piezoelectric/photoluminescence effects, which originated from the combination of the electromechanical properties and the photoluminescence effect through introducing the rare-earth elements (Pr and Eu) into the (Bi_0.5Na_0.5)TiO₃–BaTiO₃ ceramics with the composition around the morphotropic phase boundary. Compared to the pure piezoelectric ceramic, the proposed system simultaneously exhibited enhanced ferroelectric, piezoelectric, dielectric properties along with strong photoluminescence effects, which exhibited potential applications in sensor, and electro-mechano-optical integration. In addition, the present work also provides a promising path for us to fabricate multifunctional composites.     

Polarization mechanism of ferroelectric lattice instability in crystals

It is shown that the intercell dipole-dipole (polarization) interaction lowers the frequencies of the polar transverse-optical (TO) lattice vibrational modes (to a greater extent, the larger the corresponding dipole oscillator strengths) and can be a cause of ferroelectric instability in crystals. A model-independent method for determining the frequencies, eigenvectors, and dipole oscillator strengths of all the polar TO modes for a crystal with a suppressed polarization interaction from the known values of these quantities for the corresponding real crystal is proposed. The results of the corresponding calculations for several compounds with perovskite structure (SrTiO₃, BaTiO₃, KTaO₃, KNbO₃, and KCoF₃) and rutile structure (TiO₂, SnO₂, SiO₂, CoF₂, and NiF₂) are presented, and the nature of the ferroelectric soft mode in oxides with crystal structures of these two types is discussed. Fiz. Tverd. Tela (St. Petersburg) 39, 687–693 (April 1997)     

Investigation of ferroelectric phase transition for modified barium titanate in multilayer ceramic capacitors by in situ Raman scattering and dielectric measurement

The ferroelectric phase behaviors of modified BaTiO₃ in X7R multilayer ceramic capacitors (MLCCs) were investigated by dielectric measurements and in situ Raman scattering. The in situ thermo-Raman scattering shows that because of a residual stress existing in the MLCCs, the tetragonal to cubic phase transition for modified BaTiO₃ in MLCCs takes place over a wide temperature range of 373 K to 473 K, suggesting a diffuse-like characteristic which can be well explained by a modified phenomenological thermodynamic model, while the dielectric measurement indicates that the tetragonal to cubic transition occurs at 393 K. A disagreement exists between the two experimental results. Furthermore, a dc field-induced paraelectric to ferroelectric transition was identified by the two measurement techniques, but their phase-transition mechanisms are different. The dielectric measurement reveals the polar-micro-region to macro-domain transformation in the shell part of the core–shell structure while the in situ Raman scattering shows the cubic to tetragonal transition under a dc bias field. PACS 74.20.De; 77.22.Ch; 77.84.Dy; 77.80.Bh; 78.30.-j     

Piezoelectric properties of oriented Z′ cuts of PZT-type ferroelectric ceramics

The piezoelectric and dielectric properties of oriented β°Z′ cuts (β=0, 15, 30, 45, 60°) of piezoelectric crystals of TsTS-83G (lead zirconate titanate) composite are studied. A static model is proposed for the case of a maximally polarized ceramic based on the conditions of complete and partial stability of the polar axes c with allowance for their nonuniform distribution for 180° and 90° domain reorientations. It is found that the TsTS-83G piezoelectric composite does not exhibit anisotropy in the piezoelectric coefficient d ₃₃ ^′ when the axis of the Z′ cut is rotated in the ZY plane relative to the XYZ coordinate system. Zh. Tekh. Fiz. 68, 75–79 (July 1998) Deceased.     

Lead-free ferroelectric BaTiO3 doped-(Na0.5Bi0.5)TiO3 thin films processed by pulsed laser deposition technique

The difficulties in synthesizing phase pure BaTiO₃ doped-(Na_0.5Bi_0.5)TiO₃ are known. In this work, we reporting the optimized pulsed laser deposition (PLD) conditions for obtaining pure phase 0.92(Na_0.5Bi_0.5)TiO₃-0.08BaTiO₃, (BNT-BT_0.08), thin films. Dielectric, ferroelectric and piezoelectric properties of BNT-BT_0.08, thin films deposited by PLD on Pt/TiO₂/SiO₂/Si substrates are investigated in this paper. Perovskite structure of BNT-BT_0.08 thin films with random orientation of nanocrystallites has been obtained by deposition at 600 °C. The relative dielectric constant and loss tangent at 100 kHz, of BNT-BT_0.08 thin film with 530 nm thickness, were 820 and 0.13, respectively. Ferroelectric hysteresis measurements indicated a remnant polarization value of 22 μC/cm² and a coercive field of 120 kV/cm. The piezoresponse force microscopy (PFM) data showed that most of the grains seem to be constituted of single ferroelectric domain. The as-deposited BNT-BT_0.08 thin film is ferroelectric at the nanoscale level and piezoelectric.     

Ferroelectric phase transition in LaBSiO5 crystals from results of thermal and dielectric measurements

The specific heat of the ceramic and the permittivity of a single-crystal sample of LaBSiO₅, a new ferroelectric in the stilwellite family, were measured in a temperature range which includes the phase transition point (T _C=140 °C). The excess entropy of the phase transition ΔS=1.05 J/mol · K and the Curie-Weiss constant C _C-W=3.2×10³ K were determined. The results indicate that the phase transition in this crystal is of a “mixed” nature and exhibits features of a displacement-type transition and an order-disorder transition. Fiz. Tverd. Tela (St. Petersburg) 40, 1310–1312 (July 1998)     

Bipolar cycling effects in BiFeO3–BaTiO3 piezoelectric ceramics

BiFeO₃–BaTiO₃ (BF-BT) lead-free piezoelectric system has been paid much attention due to good piezoelectric properties and high Curie temperature. Poling is a process to align ferroelectric domains and increase the piezoelectric coefficients. During the poling process, unipolar direct current (dc) electric fields were applied conventionally, but recently bipolar alternating current (ac) cycling was reported to improve piezoelectric properties in rhombohedral structure piezoelectric materials. We investigated the effects of dc-poling and ac-cycling in BF-BT ceramics. The d₃₃ increased from 210 pC/N with dc-poling to 240 pC/N with ac-cycling in the morphotropic phase boundary region of BF-BT with domain engineering. This improvement of piezoelectric properties with ac-cycling was consistent with the structural evolution related to ferroelectric domains.     

Diluted magnetic ferroelectric effect in BaTi0.9Hf0.05Co0.05O3 ceramic

We report that magnetism, especially ferromagnetism, can be induced in a nonmagnetic ferroelectric oxide such as barium titanate (BaTiO₃) with choosing of suitable dopants. High-density polycrystalline sample of BaTi_0.9Hf_0.05Co_0.05O₃ was prepared using solid-state sintering route, and the effect of Co and Hf substitution on structural, magnetic and ferroelectric properties of BaTiO₃ was studied. The magnetic order obtained in the above sample is of intrinsic in nature. Ferromagnetic behavior shown in the BaTi_0.9Hf_0.05Co_0.05O₃ ceramic may be attributed to the effective exchange interactions between oxygen vacancies and Co ions. BaTi_0.9Hf_0.05Co_0.05O₃ ceramic has also shown ferroelectric (lossy type) behavior.     

Ferroelectric properties of SrTiO3-PbTiO3 solid solutions

Dielectric properties of ceramic samples of Sr_1−x Pb_xTiO₃ solid solutions for x varying from 0 to 0.3 have been studied. The ferroelectric phase transition in this system has been established to persist down to x=0.005. Within the x values of 0.002 to 0.05, the ferroelectric transition temperature is shown to follow the relation T _c=A(x−x _c)^1/2, with A=440 K and x _c=0.002. Fiz. Tverd. Tela (St. Petersburg) 39, 714–717 (April 1997)     

质子对BaTiO3薄膜辐照损伤的计算机模拟

本文先应用分子动力学模拟BaTiO₃体系在初级击出原子(primary knock-on atom, PKA)轰击下缺陷产生和复合的动力学过程, 模拟结果表明：PKA的方向和能量对缺陷数目有重要影响, 并计算了Ba, O和Ti原子的平均位移阈能分别为69 eV, 51 eV和123 eV, 远大于SRIM程序默认的位移阈能25 eV. 然后应用蒙特卡罗软件包SRIM, 模拟质子在BaTiO₃薄膜中的能量损失过程, 比较位移阈能对模拟结果的影响, 分析质子能量和入射角度对空位数量以及分布的影响. 结果表明空位数量随着质子能量增加而增加, 增加的速率随能量的增加是降低的;当入射角度大于60°, 空位数量随入射角增大而明显减少.