MPB Region Research Articles

Influences of Liquid‐Phase Sintering on Structure, Grain Growth, and Dielectric Behavior of PbZr0.52Ti0.48O3 Ceramics

In this work, to formulate piezoceramic systems such as PbZr0.52Ti0.48O3 (PZT) for low‐temperature co‐fired ceramic (LTCC)‐based devices, liquid‐phase sintering approach is demonstrated. ZnO–B2O3 (ZB) binary glass system is used as sintering aid. X‐ray diffraction (XRD) study confirms the formation of morphotropic phase boundary (MPB; tetragonal + rhombohedral) in PZT prepared by hydrothermal route. ZB is found to induce change in tetragonal/rhombohedral ratio in MPB of PZT. 1%ZB in PZT is found to raise the tetragonality from 71% to 92% in MPB region of PZT. ZB addition in PZT has reduced the sintering temperature from 1250 to 825°C for relative density about 91% with sustaining MPB phase. 1% ZB content is optimal percentage to enhance sinterability and relative density. Uniform dispersion of glass in PZT matrix is confirmed by SEM images. ZB content in PZT is found to controlling grain growth during sintering. Highest dielectric constant and lowest dielectric loss with low sintering temperature (825°C) of 1%ZB among all glass added in PZT exhibit technical suitability of 1%ZB + PZT to use as LTCC‐based energy storage devices.

Lead-free piezoelectric ceramics based on (1 − x)BNKLLT–xBCTZ binary solid solutions synthesized by the solid-state combustion technique

The aim of this work is to improve the electrical properties of BNKLLT ceramics with the addition of BCTZ. New binary (1 − x)BNKLLT-xBCTZ lead-free piezoelectric ceramics with different x contents between 0 and 0.10 (step 0.02) were fabricated by the solid-state combustion technique, where glycine was used as a fuel. The influences of x concentration on the phase evolution, morphology, and electrical behavior were investigated. The phase formation exhibited a coexistence of rhombohedral and tetragonal phases in all samples. With the increasing x content, the phase formation was dominated by a higher tetragonality. The average gain size continuously reduced from 1.52 to 0.96 µm when x content was increased. The maximum dielectric temperature (TSA) of these ceramics decreased with the increasing x content. The ferroelectric properties were further weakened with the increasing x content. The MPB region was obtained at x content of around 0.04 producing this sample and showed the highest dielectric constants (er = 2720 and eSA = 6110) and an excellent piezoelectric constant (d33 = 295 pC/N).

Temperature dependent spectroscopic ellipsometry and Raman scattering of PbTiO_3-based relaxor ferroelectric single crystals around MPB region

To discover intrinsic relationship between optical bandgap and structural transformations in relaxor ferroelectric single crystals, electronic band structures and dielectric functions of xPb(In1/2Nb1/2)O3-(1 − x − y)Pb(Mg1/3Nb2/3)O3-yPbTiO3 single crystals (x∼0.27–0.28, y∼0.29–0.35) around morphotropic phase boundary have been investigated by variable-temperature (200–750 K) spectroscopic ellipsometry. It was found that the discontinuous evolution from the second derivative of dielectric functions corresponds to structural transformation patterns. Using the SCP (standard critical point) model, four typical interband transitions (Ea∼2.8 eV, Eb∼3.6 eV, Ec∼4.6 eV, and Ed∼5.4 eV) can be uniquely assigned. These interband transitions are mainly attributed to the contributions from B-O bonds and multiphase coexistence. Furthermore, a modified phase diagram based on interband transition variations with the temperature and PT composition for PIMN-PT crystals was provided. In order to verify the accuracy of phase transition temperature, temperature-dependent low-wavenumber Raman scattering was used as a support. The present results provide important supports for the theoretical model, which establish a quantitative relationship between the electronic transition and structural transformation for ferroelectric oxides.

Investigation of MPB region in lead free BLNT-BCT system through XRD and Raman spectroscopy

Lead free piezoelectrics [1-x{(Bi0.96La0.04)0.5Na0.5TiO3}−x(Ba0.90Ca0.10TiO3)] (BLNT-BCT) with compositions x ≤ 0.20 have been synthesized by a semi-wet route and the compositions around the MPB region have been systematically investigated using x-ray diffraction and Raman spectroscopy. X-ray diffraction analysis confirms phase formation without any traces of secondary phases. Rietveld refinement of x-ray diffraction data revealed different structural symmetry for a different range of compositions viz., (i) rhombohedral (R3c) [x ≤ 0.08] (ii) rhombohedral (R3c) + tetragonal (P4mm) (MPB) [0.10 ≤ x ≤ 0.15] (iii) tetragonal (P4mm) [0.15 < x ≤ 0.20], which is confirmed by Raman spectroscopy. The structural phase transitions have been correlated with piezoelectric properties and the composition with x = 0.12 depicts better piezoelectric properties amongst studied compositions, which is attributed to the coexistence of rhombohedral and tetragonal phases.

Structural and dielectric anomalies near the MPB region of Na0.5Bi0.5TiO3–SrTiO3 solid solution

In the present attempt, (1 − x)NBT(Na0.5Bi0.5TiO3)–xST(SrTiO3) (x = 0.24–0.28) solid solutions are studied near the MPB region to investigate short-range structural and dielectric anomalies.

Electric field induced polarization and strain of (Bi1/2Na1/2)TiO3–BaTiO3 ceramics

This study investigated the whole composition range of the electric field induced polarization and strain of (1−x)(Bi0.5Na0.5)TiO3–xBaTiO3 ceramics fabricated by a conventional solid-state reaction. In most of the composition regions (x<0.7) except for the MPB region (0.06≤x<0.08), saturated square-shape P–E loops and large negative strains in the S–E curves, along with a high coercive field and a large remnant polarization, were obtained. In these composition ranges, the remnant polarization and maximum positive strain decreased gradually with an increasing BaTiO3 content and the coercive field reached the maximum at x=0.4. The high coercive field was intrinsically affected by (Bi0.5Na0.5)TiO3, possessing a doubling of the unit cell owing to octahedron tilting and compositional ordering. At 0.7≤x, the crystal structure became a simple tetragonal structure, and the remnant polarization and the coercive field significantly decreased with an increasing BaTiO3 content.

A lead-reduced ferrolectric solid solution with high curie temperature: BiScO3–Pb(Zn1/3Nb2/3)O3–PbTiO3

A lead-reduced ternary ferroelectric solid solution system of BiScO3–Pb(Zn1/3Nb2/3)O3–PbTiO3 (BS–PZN–PT) in the form of the ceramic was investigated for its structure and properties in order to develop novel ferroelectric materials with high Curie temperature and good piezoelectric properties. A morphotropic phase boundary region was delimited in this system between rhombohedral and tetragonal phases. The Curie temperature TC of this ternary system varied from 321°C to 131°C and the coercive fields EC from 24.6kV/cm to 8.62kV/cm. The piezoelectric coefficient d33 varies in the range of 100–320pC/N with increasing PZN content. Those compositions within the MPB region possess good comprehensive piezoelectric properties, for example, d33 and TC of compositions with 0.32BS–0.15PZN–0.53PT, 0.34BS–0.15PZN–0.51PT and 0.28BS–0.30PZN–0.42PT are 313pC/N and 319°C, 300pC/N and 304°C, 320pC/N, and 236°C, respectively. The high TC and d33 make it a promising material for high-powder ultrasound transducers for use over a wide temperature range.

Phase formation, microstructure and dielectric properties of Bi0·5(Na0·74K0·16Li0·10)0·5TiO3–Ba(Zr0·5Ti0·95)O3 ceramics prepared via combustion technique

Binary lead free electroceramics with the composition of (1–x)Bi0·5(Na0·74K0·16Li0·10)0·5TiO3–x(BaZr0·05Ti0·95)O3 or BNKLT–100xBZT with 0·025≤x≤0·150 were synthesised via the combustion technique. The results showed how BZT content affects typical properties of a BNKLT–100xBZT system such as phase formation and dielectric properties. The XRD investigation revealed that BNKLT–100xBZT exhibits the coexistence of rhombohedral and tetragonal phases. By adding BZT, the rhombohedral phase decreases and tetragonal phase increases. From a dielectric properties investigation, BNKLT–100xBZT shows two dielectric loss peaks at ∼190 and ∼320°C defined as Td and Tm respectively. Increasing the BZT fraction makes Tm shift to a lower temperature but has no effect on the Td shifting. The maximum ϵr and ϵmax with their respective values of 1380 and 4050 are observed from the sample with the composition BNKLT–5BZT, which can be attributed to its location near the MPB region.

Enhanced piezoelectric properties of 0.55Pb(Ni1/3Nb2/3)O3-0.135PbZrO3- 0.315PbTiO3 ternary ceramics by optimizing sintering temperature

0.55Pb(Ni1/3Nb2/3)O3-0.135PbZrO3-0.315PbTiO3 (PNN-PZ-PT) ternary piezoelectric ceramics with excess 1.0 wt.% PbO were synthesized by the conventional solid-state reaction method at 1175–1300 °C for 2 h, respectively. The influence of sintering temperature (T s) on microstructure, piezoelectric, dielectric, and ferroelectric properties were systematically investigated. The results of XRD and Raman scattering spectra demonstrated that a typical perovskite structure with mainly rhombohedral symmetry near the MPB region were obtained for all the samples. The tetragonal phase content was increased slightly with the increase of sintering temperature. In addition, with increasing T s the average grain size increases while the density decreases were also found. The results of electrical measurements confirmed that piezoelectric constant, dielectric constant, remnant polarization were firstly increased and then decreased with the increase of sintering temperature. The optimum and remarkable enhanced electrical properties of d 33 = 1070 pC/N, k p = 0.69, e r = 8710, tanδ = 0.026, P r = 24.08 μC/cm2, and E c = 3.2 kV/cm were obtained for the sample sintered at 1250 °C for 2 h. Meanwhile, the sample exhibits a typical relaxor ferroelectric behavior with the maximum dielectric constant e m =24541 at Curie temperature T c = 113.3 °C at 1 kHz.

A Pb(In1/2Nb1/2)O3–Pb(Zn1/3Nb2/3)O3–PbTiO3 ternary ferroelectric system with high TC and high piezoelectric properties

(0.79−x)Pb(In1/2Nb1/2)O3–0.21Pb(Zn1/3Nb2/3)O3–xPbTiO3 (x=0.23–0.35) ternary ferroelectric system in the form of ceramics have been synthesized. Its structure and properties have been studied by X-ray powder diffraction and electric measurements. A morphotropic phase boundary region has been determined in the composition range of 0.28<x<0.32, where the Curie temperature TC and the rhombohedral–tetragonal phase transition temperature TRT were found to vary from 243°C to 295°C and 145°C to 191°C, respectively, much higher than PMNT and PZNT systems. The compositions within MPB region exhibit excellent piezoelectric properties such as piezoelectric coefficient d33>646pC/N, TRT>145°C, TC>273°C and EC>13kV/cm for 0.5PIN–0.21PZN–0.29PT and 0.49PIN–0.21PZN–0.30PT, making the ceramics of this system a promising material for high power and high temperature application.

A correlated electron diffraction, in situ neutron diffraction and dielectric properties investigation of poled (1-x)Bi0.5Na0.5TiO3-xBaTiO3 ceramics

A correlated electron diffraction, temperature-dependent in situ neutron diffraction, and temperature-dependent dielectric properties investigation of poled (1-x)Bi0.5Na0.5TiO3-xBaTiO3 (BNTBT100x) (x = 0.04, 0.07, and 0.12) samples has been carried out. The results show that the depolarization temperature, Td, of the rhombohedral BNTBT 4 sample is associated with the disappearance of G ± ½ [111]*p satellite reflections and a-a-a- octahedral tilting while that of the BNTBT 12 sample is associated with a metrically tetragonal to metrically cubic or pseudo-cubic symmetry. In the case of the poled BNTBT 7 sample in the MPB region, the dielectric properties show a quite distinct two stage transition from a room temperature clearly metrically tetragonal phase again to a metrically cubic or pseudo-cubic symmetry above 150 °C. There is no apparent change in its average structure in vicinity of Td in BNTBT 7. Electron diffraction shows the presence of considerable octahedral tilt twin disorder in all three samples.

Phase evolution and ferroelectric behavior in BaTiO3-BiScO3-PbTiO3 ceramics

Phase evolution and ferroelectric behavior in 0.8BaTiO3-(0.2-x) BiScO3-xPbTiO3 ceramics, x = 0-0.20, has been investigated in this paper. The phase assemblage and lattice parameters indicate the appearance of tetragonal-rhombohedral phase transition and the existence of a MPB region in the composition range x = 0.15-0.20. All these compositions exhibit relaxor ferroelectric behavior due to cation disorder for the substitution on the A-site by Bi and on the B-site by Sc. The dielectric permittivity of the specimens as well as the polarization decreases with increasing BiScO3. However, close to MPB region, the composition with dominance of rhombohedral phase (x = 0.15) exhibits higher remnant polarization than that with tetragonal for the more reorientational directions of the rhombohedral phase than that of the tetragonal one (x = 0.17).

Piezoelectric and Dielectric Properties of (Bi0.5Na0.5)TiO3-Ba(Ti0.95Zr0.05)O3 System

The morphotropic phase boundary of bismuth sodium titanate (BNT) and barium zirconate titanate (BZT) ceramics were study. In the case of (1-x)BNT-xBZT where x = 0.06 to 0.12 mol. The solid solution ceramics which have the combine phases between rhombohedral and tetragonal are obtained at x = 0.06 to 0.11 mol. The maximum of piezoelectric and dielectric constants are obtained for 0.93BNT-0.07BZT ceramics at 161 pC/N and 1839, respectively. This may be indicated that this composition is nearly existed of MPB region.

Structure and Electrical Properties of Pb(Ni&lt;sub&gt;1/3&lt;/sub&gt;Nb&lt;sub&gt;2/3&lt;/sub&gt;)O&lt;sub&gt;3&lt;/sub&gt;-Pb(Zr/Ti)O&lt;sub&gt;3&lt;/sub&gt; Relaxors

Ceramics with the type of 0.50Pb(Ni1/3Nb2/3)O3-0.15PbZrO3-0.35PbTiO3 were synthesized by conventional mixed-oxide technique. The dielectric and ferroelectric properties of this composition were investigated in detail. Frequency dispersion and diffuse phase transition were observed in the dielectric behaviors. The revealed electrical properties are εm = 22388, Pr = 21.449 μC/cm2 and Ec = 5.191 kV/cm. XRD experiments demonstrate that this composition is within the MPB region, which may help to explain the super electrical properties discussed in this study.

EFFECT OF YTTRIUM ON DIELECTRIC, PYROELECTRIC AND PIEZOELECTRIC PROPERTIES OF PBN FERROELECTRICS

Materials with batch formula Pb (1-x-3y/2) R y Ba x Nb 2 O 6, where R=Y, (1-x)=0.73, 0.63, 0.53 and y=0.00, 0.02 have been prepared by the double sintering method. Substitution of yttrium (Y) restored tetragonal symmetry of PBN but reduced lattice parameters, cell volume and enhanced the density. Transition temperature of PBN has decreased due to the substitution of Y3+. Enhanced room temperature spontaneous polarization (Ps)=149.97 μ C/sq. cm has been observed in PBN53, which is above MPB, whereas enhanced value of Ps=112.74 μ C/sq. cm is found in Y: PBN63 at MPB region. The room temperature Pyroelectric coefficient (PRT=1.07) has been observed in the composition where maximum volume of Ps is obtained. Similarly, enhanced values of piezoelectric coefficients Kp=0.244, Kt=0.353, K31=0.131, d31=60, d33=159 and g31=3.65 have also been found in the same material PBN53. Substitution of Yttrium enhanced the stiffness constant 13.59 in PBN 73 to 14.27 of Y: PBN73.

Thermal expansion of phase transformations in(1−x)Pb(Mg1∕3,Nb2∕3)O3−xPbTiO3: Evidence for preferred domain alignment in one of the ⟨001⟩ directions for melt-grown crystals

Thermal expansion measurements on unpoled, multidomain, single crystals of PMN-PT in the MPB region reveal that one of the ⟨001⟩ directions is different than the other two, contrary to the crystallographic equivalency that is expected for threefold rotations about ⟨111⟩ derived from the prototypic-cubic phase. This unexpected behavior may be related to the method of seeded crystal growth. On heating into the tetragonal phase, the unique axis persists, consistent with the preferential alignment of $c$-axis domains. Poling along the unique direction further enhances the anisotropy in thermal expansion coefficients, leading to an increase in the magnitude of the strain induced on heating through the subsequent rhombohedral-to-tetragonal and tetragonal-to-cubic phase transformations. Room-temperature poling in the rhombohedral phase in a direction normal to the unique direction reorients the preferred domain alignment in the higher temperature tetragonal phase. This realignment disappears upon further heating into the high-temperature cubic phase, i.e., thermal depoling reestablishes the original unique direction. When the room-temperature poled crystals are heated under open-circuit conditions, the temperature at which the tetragonal-to-cubic phase transformation is completed is shifted to higher temperatures relative to unpoled crystals, indicating an increase in the temperature range of stability for the tetragonal phase as a result of incomplete randomization of domain orientations at the rhombohedral-to-tetragonal phase transformation. Under short-circuit conditions, the tetragonal-to-cubic phase transformation temperature is not shifted, indicating a complete randomization of polarization directions on heating above the rhombohedral-to-tetragonal phase transformation temperature. The thermal expansion characteristics for the phase transformation behavior are related to poling conditions and dielectric properties.

EFFECT OF THE HEATING RATE FOR PREHEATING PROCESS ON THE COMPOSITION AND PHASE TRANSFORMATION OF SOL-GEL DERIVED LEAD ZIRCONATE TITANATE THIN FILM

ABSTRACT Lead zirconate titanate (PZT, 53/47) thin firms were successfully fabricated on multi-layers substrate by the spin-coating sol-gel process. The effects of different heating rates on the composition and phase transformation of PZT films were discussed. This study focused on the slow heating rate (1°C/min) to the first preheating step (150°C) and to second pyrolysis step (350°C). By XRD method, PZT films contained entirely pure perovskite phase annealing at 700°C for 30 min for the slow heating rate procedure. By using EPMA analysis, the composition of PZT thin film derived by this procedure was indeed located at the MPB region. Furthermore, the phase coexistence was evidenced by the BEI analysis.

Piezoelectric and pyroelectric properties of (Bi0.5Na0.5)0.94Ba0.06TiO3/P(VDF-TrFE) 0–3 composites

Bismuth sodium barium titanate [(Bi0.5Na0.5)0.94Ba0.06TiO3 or BNBT] ceramic powder have been incorporated into a polyvinylidene fluoride-trifluoroethylene [P(VDF-TrFE) 70/30 mol%] copolymer matrix to form 0–3 composites. With the composition near the MPB region, BNBT has relatively high piezoelectric and dielectric properties. P(VDF-TrFE) ferroelectric copolymer films can be poled to give piezoelectric and pyroelectric performance without prior mechanical stretching. The composites were prepared using solvent casting to disperse the ceramic powder homogeneously in the copolymer matrix. Composites with BNBT volume fraction ϕ ranging from 0.05 to 0.30 were fabricated using a hot-press method. The piezoelectric and pyroelectric coefficients of the composites were studied as a function of ϕ under different poling conditions. As BNBT has a low relative permittivity, so it is relatively easy to pole the BNBT ceramic inclusion. Hence, the BNBT 0–3 composites were found to have better pyroelectric properties than that of the lead zirconate titante PZT/P(VDF-TrFE) 0–3 composites.

Influence of Pr 2 O 3 and Nd 2 O 3 on Ferroelectric and Pyroelectric Properties of Tungsten Bronze Structured BSNN Ceramics

Present communication describes the preparation and the influence of Pr 2 O 3 and Nd 2 O 3 on structure, ferroelectric, dielectric, pyroelectric and resistivity properties of (Ba 1-x Sr x ) 2 NaNb 5 O 15 [BSNN] compositions at and around x = 0.6, MPB region. Substitution of Pr 2 O 3 /Nd 2 O 3 decrease the cell volume and Curie temperature and enhance the room temperature dielectric constant. The room temperature pyroelectric coefficients are observed to be in the order of 10-9 C/cm 2 °C. Higher figure of merit FM RV , FM RN and FM RI values of the order 10-14 CM/J, 10-12 CM/J and 10-11 CM/J respectively are observed in both Pr/Nd:BSNN compositions. Resistivity studies revealed a PTCR behavior.