Coexistence Of Tetragonal Phase Research Articles

Piezoelectric and dielectric properties of B2O3-added (Ba0.85Ca0.15)(Ti0.915Zr0.085)O3 ceramics sintered at low temperature

Abstract In this paper, the (Ba0.85Ca0.15)(Ti0.915Zr0.085)O3+0.004CuO lead-free piezoelectric ceramics have been fabricated using the conventional ceramics processing in air and the effect of B2O3 addition on their phase structure, microstructure, and piezoelectric properties of (Ba0.85Ca0.15)(Ti0.915Zr0.085)O3+0.004CuO+xB2O3 ceramics were systematically investigated. The B2O3 diffuses into the BCTZ lattice to form a stable soild solution, rhombohedral and tetragonal phase coexistence is observed in the ceramics with the 1.0

Large piezoelectricity in Pb-free 0.96(K0.5Na0.5)0.95Li0.05Nb0.93Sb0.07O3−0.04BaZrO3 ceramic: A perspective from microstructure

We employ transmission electron microscopy to explore the reason for large piezoelectricity (d33≈400pC/N) in a Pb-free 0.96(K0.5Na0.5)0.95Li0.05Nb0.93Sb0.07O3 −0.04BaZrO3 ceramic from microstructure. The result shows that the high piezoelectricity corresponds to a miniaturized nanodomain configuration in a domain hierarchy. The nanodomains disappear on heating accompanied by a reduction in d33 value. Further convergent beam electron diffraction study reveals a coexistence of tetragonal and orthorhombic phase, which indicates that large piezoelectricity of KNLNS0.07-BZ may stem from easy polarization rotation due to low polarization anisotropy on the tetragonal-orthorhombic phase boundary.

Good temperature stability and fatigue-free behavior in Sm2O3-modified 0.948(K0.5Na0.5)NbO3–0.052LiSbO3 lead-free piezoelectric ceramics

Abstract The rare-earth oxide Sm 2 O 3 -doped 0.948(K 0.5 Na 0.5 )NbO 3 –0.052LiSbO 3 (abbreviated as KNN-LS5.2) lead-free piezoelectric ceramics were prepared using conventional solid sintering method. The effects of Sm 2 O 3 on the phase structure, electrical properties, temperature stability and fatigue behavior of KNN-LS5.2 ceramics were systematically studied. Results showed that Sm 2 O 3 substitution into KNN-LS5.2 induced a phase transition from coexistence of orthorhombic and tetragonal phase to a pseudocubic phase with a normal-relaxor ferroelectric transformation, and correspondingly shifted the polymorphic phase transition (PPT) below room temperature. Accordingly, the temperature stability and fatigue behavior of the modified ceramics were significantly improved. It was found that the KNN-LS5.2 ceramics with 0.6 mol% Sm 2 O 3 addition exhibited nearly temperature independent properties and fatigue-free behavior, together with its good electrical properties ( d 33 * = 167 pm/V, d 33 = 120 pC/N, k p = 33%, Q m = 101, ϵ r = 1326, tan δ = 4.6%). The results suggest that this material should be an attractive lead-free material for piezoelectric applications.

High piezoelectricity in low-temperature sintering potassium–sodium niobate-based lead-free ceramics

Here we have realized three goals in a new potassium–sodium niobate material using CuO as sintering aid, such as low temperature sintering, the suppression in the loss of alkali metals, and attaining a high d33. Low-temperature sintered 0.96(K0.46Na0.54)Nb0.95Sb0.05O3–0.04Bi0.5(Na0.82K0.18)0.5ZrO3 ceramics were made conducting by adding CuO using an ordinary ceramic fabrication technique. The sintering temperatures drop from 1095 °C to 950 °C when the CuO content is increased from 0 to 2.5 wt%, and the K and Na loss could be also prevented under a low processing temperature. In addition, the ceramics undergo a phase transition with increasing CuO content, such as from a rhombohedral–tetragonal phase coexistence to the mixture of both rhombohedral–orthorhombic and orthorhombic–tetragonal phase boundaries. The inhomogeneous Cu2+ distributions become more obvious as the CuO content rises, i.e., the excess Cu2+ aggregates at the small grains region for a low CuO content (x ≤ 1.5), and at the small and large grains zones for x = 2.5. The dielectric constant gradually decreases as the CuO increases, and the dielectric loss is lowered by adding CuO content. A well polarization vs. electric field (P–E) loop is seen in the ceramics with x ≤ 2.5, and those with x = 2.5 possess a high d33 of 310 pC N−1 even if the sintering temperatures drop down to 950 °C. As a result, it is an efficient way to promote the piezoelectricity of copper oxide-modified alkaline niobate ceramics using a low-temperature sintering technique.

Phase evolutions and electric properties of BaTiO3 ceramics by a low-temperature sintering process

BaTiO3 (BT) nanoparticles were synthesized by a modified polymeric precursor method in a weak acid solution. The synthesized process of BT precursor with increasing calcination temperature was investigated through thermal analysis (DTA/TG), X-ray diffraction, transmission electron microscope and Fourier-transform infrared spectroscopy. Good dispersive and homogeneous cubic BT nanoparticles were calcined at 800 °C, whereas dense BT ceramics were sintered at ~1,160 °C. The present results showed that the dielectric, piezoelectric and ferroelectric properties of BT ceramics were dependent on the ceramics densification and crystallographic structure. The excellent electric properties (P r = 10.5 μC/cm2, d 33 = 217 pC/N, k p = 0.32 %) were found at a sintering temperature of 1,160 °C, which was due to the coexistence of tetragonal and orthorhombic phase. The depressed electric properties at higher sintering temperature were associated to oxygen vacancies and impurity phases. In addition, phase evolutions of BT nanoparticles and ceramics were all stated in detail.

Investigation of orthorhombic–tetragonal structural crossover in (Ba0.92Ca0.08)(Zr0.05Ti0.95)O3

The orthorhombic to tetragonal phase transition in (Ba0.92Ca0.08)(Zr0.05Ti0.95)O3was investigated using high-temperature X-ray diffraction between 260 and 333 K. The results established the presence of tetragonal (P4mm) and orthorhombic (Amm2) phase co-existence in the temperature range of 293 ≤T≤ 313 K. The tetragonal phase was found to increase from 27% at 293 K to 76% at 313 K. The structural refinement and line-profile analysis ruled out the presence of an intermediate monoclinic structure duringP4mm→Amm2 crossover. The analysis shows a pure orthorhombic (Amm2) structure forT< 293 K and tetragonal forT> 313 K.

Enhanced relaxor ferroelectric behavior of BCZT lead-free ceramics prepared by hydrothermal method

Abstract Ceramics in the solid solution system, Ba 0.9 Ca 0.1 Ti 0.9 Zr 0.1 O 3 – x Nd 3+ , were prepared via a hydrothermal method and were assisted by microwave sintering, and the effects of Nd 3+ -doping on the electrical properties of Ba 0.9 Ca 0.1 Ti 0.9 Zr 0.1 O 3 were studied. All the samples showed single perovskite structure without a second phase, and a change from the rhombohedral phase to the coexistence of tetragonal and cubic phase occurred at x ≥0.025. The dielectric constant and dielectric loss both decreased with increasing Nd 3+ content at 0.000≤ x ≤0.015 and the sample with x =0.020 showed giant permittivity with higher dielectric loss. At x =0.025 and 0.030, the T C significantly decreased and the samples exhibited optimistic relaxor behavior with excellent frequency dispersion. The P r decreased with increasing Nd 3+ content and the samples with x =0.025 and 0.030 showed P–E loops with lower polarization loss. The piezoelectric constant ( d 33 ) measured at room temperature increased with increasing Nd 3+ addition and exhibited the maximum value at x =0.025. The ferroelectric and piezoelectric properties could not be detected at samples with x =0.020.

Two-Phase Coexistence and Multiferroic Properties of Cr-Doped BiFeO3 Thin Films

Pure BiFeO 3 (BFO) and Cr-doped BiFe 0.97 Cr 0.03O3 (BFCO) thin films were successfully prepared on F-doped SnO 2 conductive film (FTO)/glass (SnO 2: F) substrates by a sol–gel method. The effect of Cr doping on the structure, ferroelectric, and ferromagnetic properties of the BFO and BFCO thin films have been investigated. X-ray diffraction, Rietveld refined X-ray diffraction (XRD) patterns, and Raman spectroscopy results clearly reveal that the BFCO thin film is characterized by the coexistence of two phases (trigonal and tetragonal). Moreover, the various leakage mechanisms of both thin films have also been studied. The improved ferroelectricity with remnant polarization (Pr) of about 2Pr = 68.68 μC/cm 2 under an applied electric field of 1,181.8 kV/cm and enhanced ferromagnetism with saturation magnetization (Ms) of Ms = 0.93 emu/cm 3 have been observed in the BFCO thin film. The improved electrical properties of the BFCO thin film are ascribed to the coexistence of trigonal and tetragonal phase and high valence of Cr 6+, and the Fe–O 6 octahedron distortion is enhanced due to the overlap and hybridization of Fe 3d/Cr 3d and O 2p orbits by Cr doping.

(Ba,Ca)SiO3Glass Frit 첨가에 따른 NKN-BT 세라믹스의 유전 완화 특성

We investigated dielectric relaxation properties of <TEX>$0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3$</TEX> ceramics by addition (0~0.3 wt%) of <TEX>$(Ba,Ca)SiO_3$</TEX> glass frit. All composition of <TEX>$0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3$</TEX> added <TEX>$(Ba,Ca)SiO_3$</TEX> glass frit showed the same crystallographic properties, coexistence of orthorhombic and tetragonal phase. By increasing addition of <TEX>$(Ba,Ca)SiO_3$</TEX> glass frit, the Curie temperatures of <TEX>$0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3$</TEX> ceramics were decreased, whereas maximum dielectric constants of <TEX>$0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3$</TEX> ceramics were dramatically increased. Especially the deviations of Curie temperature <TEX>$0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3$</TEX> ceramics were increased by increasing amount of <TEX>$(Ba,Ca)SiO_3$</TEX> glass frit, and it indicated that <TEX>$0.95(Na_{0.5}K_{0.5})NbO_3-0.05BaTiO_3$</TEX> ceramics added <TEX>$(Ba,Ca)SiO_3$</TEX> glass frit have relaxor characteristics.

Structure and dielectric property of Zr-doped (Na0.47Bi0.46Ba0.06K0.01)(Nb0.02Ti0.98)O3 lead-free ceramics

(Na0.47Bi0.46Ba0.06K0.01)(Nb0.02Ti0.98-xZrx)O3 lead-free ceramics (BNBKT-xZr, x = 0, 0.01, 0.02, 0.04) were synthesized via conventional solid state reaction method. Crystallite structure of the ceramics was studied using X-ray diffraction. The rhombohedral phase and tetragonal phase coexist in the BNBKT-xZr ceramics. The doping of Zr4+ into BNBKT lattice increases the percentage of the tetragonal phase. The size and shape of grains in the ceramics were affected by the doping of Zr4+ ions. For all the unpoled ceramics, two dielectric anomalies are observed in the dielectric constant-temperature curves. The maximum values of dielectric constant and corresponding temperatures change with the variation of Zr4+ amount. The doping of Zr4+ ions causes a decrease in the ferroelectric properties.

Effects of La3+ addition on the phase transition, microstructure, dielectric and piezoelectric properties of Ba0.9Ca0.1Ti0.9Zr0.1O3 ceramics prepared by hydrothermal method

Lead-free Ba0.9Ca0.1Ti0.9Zr0.1O3–xLa (x = 0.000, 0.005, 0.010, 0.015, 0.020, 0.025) ceramics were prepared by hydrothermal method and were assisted by fast microwave sintering. The effects of La3+ addition on the phase transition, microstructure, dielectric and piezoelectric properties were investigated. Single orthorhombic phase was observed in the composition of x ≤ 0.010 and the coexistence of orthorhombic and tetragonal phase were detected at x = 0.015 and 0.020, which is characterized by the broadening of (002)/(200) peaks at around 2θ ~ 45°. The ceramics show cubic phase when the x was increased to 0.025. The grain size was affected significantly by the La3+ content, reaching a maximum value of ~8.2 μm at x = 0.010. The dielectric constant decreases with the addition of small amount of La3+ and then increases sharply at x ≥ 0.015, exhibiting a PTC behavior at x = 0.020, while no TC was observed at x = 0.025. The Curie temperature (TC) always decrease with the introduction of La3+ and the dielectric loss shows a minimum value at x = 0.015. The piezoelectric constant (d33) measured at 50 °C of the ceramics were increased after the partial substitution of La3+ because of the enhancement of coexistence of orthorhombic and tetragonal phases at this temperature. Ferroelectric and piezoelectric properties can not be detected when x was increased to 0.02 while they were observed again with further addition.

Dielectric and piezoelectric properties and PTC behavior of Ba0.9Ca0.1Ti0.9Zr0.1O3−xLa ceramics prepared by hydrothermal method

Abstract Lead-free Ba0.9Ca0.1Ti0.9Zr0.1O3–xLa (x=0.000, 0.005, 0.010, 0.015, and 0.020) ceramics have been prepared by hydrothermal method and were assisted by fast microwave sintering, and the effects of La-doping on the electrical properties of Ba0.9Ca0.1Ti0.9Zr0.1O3 were studied. The single orthorhombic phase was observed in the composition of x≤0.10 and the coexistence of orthorhombic and tetragonal phase were detected at x=0.015 and 0.020. The substitution of small amount of La3+ resulted in an decreasing of dielectric constant and dielectric loss, and they both possessed a minimum value at x=0.010. With the addition of x≥0.015, the Ba0.9Ca0.1Ti0.9Zr0.1O3–xLa ceramics became semi-conductors and the PTC behavior was observed. The piezoelectric constant (d33) measured at 50 °C of the ceramics were increased after the partial substitution of La3+ because of the enhancement of coexistence of orthorhombic and tetragonal phases. The TC was decreased with increasing La3+, and the ferroelectric and piezoelectric properties cannot be detected at samples with x=0.02.

Rhombohedral–tetragonal phase boundary and electrical properties of new K0.48Na0.52Nb0.98Sb0.02O3-Bi0.5Na0.5ZrO3 lead-free piezoceramics

(1 − x)K0.48Na0.52Nb0.98Sb0.02O3-xBi0.5Na0.5ZrO3 lead-free piezoceramics were prepared by using the conventional solid-state method. In this material system, (Bi0.5Na0.5)2+ and Zr4+ can decrease the orthorhombic-tetragonal phase temperature and increase the rhombohedral–orthorhombic phase temperature. The rhombohedral–tetragonal phase coexistence is identified in the ceramics with the compositional range of 0.03 < x < 0.05. The ceramic with x = 0.04 has an enhanced piezoelectric behaviour of d33 ∼ 257 pC N−1 and kp ∼ 41%, which is three times higher than that of a pure KNN ceramic. In addition, the enhanced stability of piezoelectric and ferroelectric properties is also observed in such a ceramic. These results show that such a new lead-free material system is a promising candidate for piezoelectric devices.

Effect of Mn doping on multiferroic properties in Bi0.8Ba0.2FeO3 ceramics

Multiferroic ceramics Bi0.8Ba0.2Fe1−xMnxO3 with x=0.0, 0.05, 0.1, and 0.15 were prepared by using conventional solid state reaction method. The structural, magnetic, ferroelectric and dielectric properties were investigated. The phase transition from rhombohedral to tetragonal structure with increasing Mn substitution concentration was confirmed by using X-ray diffraction. Magnetic measurements indicated that the remanent magnetization of Bi0.8Ba0.2Fe0.95Mn0.05O3 (x=0.05) is around 2.64 times higher than that of Bi0.8Ba0.2FeO3 (x=0.0), which is probably due to the coexistence of rhombohedral and tetragonal phase that destructs the cycloidal spin structure and enhances the ferromagnetic properties significantly. The ferroelectric measurements revealed that the leakage current is significantly suppressed with an increase in the Mn content. In addition, Mn doping was found to be helpful to reduce dispersion in dielectric constant and loss, especially at lower frequencies. Furthermore, an anomaly in the dielectric constant was observed in the vicinity of the magnetic transition temperature, which could be attributed to the intrinsic magnetoelectric coupling effect. It is also worth noting that the intensity of the dielectric anomaly peak for the sample of x=0.05 was highest (~183.4) among all the samples, which indicated that the magnetoelectric coupling effect could be greatly improved by enhanced ferromagnetic properties.

Dielectric, ferroelectric, and piezoelectric properties in potassium sodium niobate ceramics with rhombohedral–orthorhombic and orthorhombic–tetragonal phase boundaries

Abstract A new phase boundary with rhombohedral–orthorhombic and orthorhombic–tetragonal phase boundaries is designed in (K 0.48 Na 0.52 )NbO 3 by adding Bi 0.5 (Na 0.7 K 0.2 Li 0.1 ) 0.5 ZrO 3 (BNKLZ), where Zr 4+ and (BNKL) 2+ are respectively used to improve the temperature of a rhombohedral phase and to decrease the temperature of an orthorhombic–tetragonal phase coexistence. These ceramics endure several continuous phase transitions with increasing BNKLZ content, i.e., an orthorhombic phase (0≤ x x =0.03), orthorhombic–tetragonal and rhombohedral–orthorhombic (O–T and R–O) phase existence (0.03 x ≤0.05), a rhombohedral phase (0.05 x ≤0.07). The ceramics with O–T and R–O have a better piezoelectric behavior as compared with other phases because of more polarization states, enhanced e r and P r , and a dense microstructure. Moreover, piezoelectric properties could be further optimized by modifying their sintering and poling temperatures. As a result, the construction of O–T and R–O phase coexistence benefits the improvement of piezoelectric properties in KNN-based ceramics.

Elastic and anelastic properties of the 0.55SrTiO3–0.45BiScO3 ceramics characteristic for relaxor ferroelectric behavior

The low‐frequency elastic and anelastic properties of the ceramic 0.55SrTiO3–0.45BiScO3 sample have been studied. Anomalous changes of the Young's modulus and the internal friction characteristic for the ferroelectric relaxors were observed at cooling below the Burns temperature at ∼585 K. The relaxor properties of this system are confirmed by dielectric measurements and attributed to the coexistence of the polar tetragonal P4mm phase and the nonpolar cubic Pm3m phase. Elastic anomaly is assumed to be due to electrostriction relationship between spontaneous polarization of polar tetragonal domains and strain of the sample. Using the special internal friction mechanism for the first order phase transition, the size of the polar phase nuclei arising at the Burns temperature was estimated to be equal to ∼20 nm.

New phase boundary and piezoelectric properties in (K, Na)NbO3 based ceramics

Abstract (1− x )K 0.48 Na 0.52 NbO 3 − x Bi 0.5 (Na 0.925 Li 0.075 ) 0.5 ZrO 3 [(1− x )KNN− x BNLZ] lead-free piezoelectric ceramics were prepared using the conventional solid-state method. Effects of BNLZ content on their microstructure and electrical properties were studied. The chemical compositions are homogeneously distributed in the ceramics, and the rhombohedral–orthorhombic and orthorhombic–tetragonal phase coexistence lies in the ceramics with the composition of 0.03 x x = 0.04) has optimal electrical properties, i.e., d 33 ∼ 242 pC/N, k p ∼ 0.33, P r ∼ 16.85 μC/cm 2 , E c ∼ 10.92 kV/mm, and T C ∼ 352 °C. In addition, a good thermal stability is also observed in the ceramic with x = 0.04. We believe that this material system is a promising lead-free piezoelectric candidate.

Low Temperature Sintering and Enhanced Piezoelectricity of Lead‐Free (Na0.52K0.4425Li0.0375)(Nb0.86Ta0.06Sb0.08)O3 Ceramics Prepared from Nano‐Powders

(Na0.52K0.4425Li0.0375)(Nb0.86Ta0.06Sb0.08)O3 powders were synthesized via sol–gel and solid‐state reaction methods as a raw material for the preparation of the ceramics. Dependence of piezoelectric properties and microstructure on sintering temperatures was investigated in this study. Sol–gel‐derived nano‐powders could be densified at a lower temperature of 940°C and exhibited excellent electrical properties after sintering at 1020°C (d33 = 424 pC/N, d33* = 780 pm/V, kp = 52.1%, and Tc = 265°C). The enhanced electric properties were most likely due to the coexistence of orthorhombic and tetragonal phase in the samples at room temperature, homogenous microstructure with fine grain and high density.

Structural and electromechanical study of Bi0.5Na0.5TiO3-BaTiO3 solid-solutions

Solid solution of (1-x)Bi0.5Na0.5TiO3-xBaTiO3 have been synthesized via conventional solid-state reaction route. Structural changes of the solid-solutions were investigated by using X-ray diffraction, Rietveld refinement Raman spectroscopy and piezoelectric studies. X-ray diffraction analysis shows a distinct 002/200 peak splitting appearing at x = 0.07 showing the coexistence of rhombohedral and tetragonal phase. Raman spectroscopy shows a splitting of (TO3) mode at x = 0.07 confirming the presence of the morphotropic phase boundary region. The dominant bands in the Raman spectra are analyzed by observing the changes in their respective peak positions, widths and intensities as the x increases. The piezoelectric properties of the solid solution increase with rise in BaTiO3 content and shows optimum value at x = 0.07 owing to the co-existence of two ferroelectric phases. Based on these results, it is suggested that the morphotropic phase boundary in the studied system lies in the composition x = 0.07.

A new (1 − x)Pb(Lu1/2Nb1/2)O3–xPbTiO3 binary ferroelectric crystal system with high Curie temperature

A series of new (1 − x)Pb(Lu1/2Nb1/2)O3–xPbTiO3 (PLN–xPT) binary ferroelectric crystals with high Curie temperature have been successfully obtained firstly by top-seed solution growth technique. A solid-state phase diagram in the low temperature range has been established based on the form of single crystals, which reveals a morphotropic phase boundary (MPB) in the range of 49–51% PT. The polarized light microscope analysis also confirms the coexistence of rhombohedral and tetragonal phase within the MPB. Furthermore, those compositions within MPB exhibit good comprehensive piezoelectric properties. For example, the crystal with composition PLN–0.49PT, showing high Curie temperature Tc = 360 °C and high rhombohedral–tetragonal phase transition temperature TRT = 110 °C, and the piezoelectric coefficient d33, electromechanical coupling coefficient k33, coercive field Ec and remanent polarization Pr are found to be 1630 pC N−1, 81%, 13.8 kV cm−1 and 26.6 μC cm−2, respectively. The large coercive field and high Tc make it a promising candidate for high power transducers in a wider temperature range.