Planar Coupling Factor Research Articles

High temperature piezoelectric ceramics based on (1 − x)[BiScO3 + Bi(Ni1/2Ti1/2)O3] − xPbTiO3

High temperature ferroelectrics are an important aspect of piezoelectric material research for many energy related applications. Some of the desired properties are high Curie temperature, large remanent polarization, and large piezoelectric coefficients. Polycrystalline perovskite ceramics of the composition (1−x)[BiScO3+Bi(Ni1/2Ti1/2)O3]−xPbTiO3 (BS-BNiT-PT), were synthesized using standard solid state processing. Room temperature X-ray diffraction revealed a perovskite phase with an observed transition from tetragonal to pseudo-cubic symmetry over the compositional range x=0.50–0.60. Compositions rich in PbTiO3 showed strong tetragonal distortions with characteristic first-order phase transitions. As the PbTiO3 content decreased dielectric measurements revealed large permittivities (er′~16,000) with relaxor characteristics up to 400°C. Ferroelectric hysteresis measurements revealed remanent polarizations as high as 31μC/cm2 at x=0.52 with relatively low coercive fields of 25kV/cm. The piezoelectric coefficients, mechanical quality, and planar coupling factors of the x=0.54 composition were 376pC/N, 13.4, and 0.148, respectively.

Structure and electrical properties of Er2O3 doped 0.82Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3 lead-free piezoelectric ceramics

Er2O3 (0–0.8wt.%)-doped 0.82Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3 (BNKT18) lead-free piezoelectric ceramics were synthesized by a conventional solid-state reaction method. The effects of Er2O3 on the microstructure and electrical properties were investigated. X-ray diffraction (XRD) data shows that Er2O3 in an amount of 0.2–0.8wt.% can diffuse into the lattice of the BNKT18 ceramics and form the pure perovskite phase. Scanning electron microscope (SEM) images indicate that the grain sizes of BNKT18 ceramics decrease with the increase of Er2O3 content; in addition, the modified ceramics have the clear grain boundary and a uniformly distributed grain size. At room temperature, the electrical properties of the BNKT18 ceramics have been improved with the addition of Er2O3, and the BNKT18 ceramics doped with 0.6wt.% Er2O3 have the highest piezoelectric constant (d33=138pC/N), the highest planar coupling factor (kp=0.2382), the highest remnant polarization (Pr=25.2μC/cm2), the higher relative dielectric constant (εr=936) and lower dissipation factor (tanδ=0.047) at a frequency of 10kHz. Moreover, the Tm and Td of the samples increase with the addition of Er2O3.

Gd2O3 doped 0.82Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3 lead-free piezoelectric ceramics

Gd2O3 (0–0.8wt.%)-doped 0.82Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3 (BNKT18) lead-free piezoelectric ceramics were synthesized by a conventional solid-state process. The effects of Gd2O3 on the microstructure, the dielectric, ferroelectric and piezoelectric properties were investigated. X-ray diffraction (XRD) data shows that Gd2O3 in an amount of 0.2–0.8wt.% can diffuse into the lattice of BNKT18 ceramics and form a pure perovskite phase. Scanning electron microscope (SEM) images indicate that the grain size of BNKT18 ceramics decreases with the increase of Gd2O3 content; in addition, all the modified ceramics have a clear grain boundary and a uniformly distributed grain size. At room temperature, the ferroelectric and piezoelectric properties of the BNKT18 ceramics have been improved with the addition of Gd2O3, and the BNKT18 ceramics doped with 0.4wt.% Gd2O3 have the highest piezoelectric constant (d33=137pC/N), highest relative dielectric constant (εr=1023) and lower dissipation factor (tanδ=0.044) at a frequency of 10kHz. The BNKT18 ceramics doped with 0.2wt.% Gd2O3 have the highest planar coupling factor (kp=0.2463).

Tantalum influence on electrical properties of lead-free (K0.4425Na0.52Li0.0375)(Nb0.93−x Ta x Sb0.07) O3 piezoelectric ceramics

Lead-free (K0.4425Na0.52Li0.0375)(Nb0.93−x Sb0.07Ta x )O3 (abbreviated as KNLNST x ) piezoelectric ceramics with x = 0.045–0.075 have been prepared by an ordinary sintering technique with sintering temperature at 1,120 °C. The results of X-ray diffraction reveal that Ta5+ has diffused into the perovskite lattice to form a solid solution. The grain growth of the ceramics was inhibited by substituting Ta5+ for Nb5+. It has been shown that the substitution of Ta decreases Curie temperature T C and orthorhombic-tetragonal phase transition temperature T O-T. Besides, the dependence of the ceramics with different Ta content on the dielectric, piezoelectric and ferroelectric properties has been investigated. The results indicate that Ta substitution provides “soft” piezoelectric characteristics, owing to improvements in d 33, k p and e r and a decease in Q m. For the ceramics with x = 0.06, the piezoelectric coefficient d 33 becomes maximum at a value of 270 pC/N, while the other electrical properties remain reasonably high: dielectric constant e r = 1,577, planar mode electromechanical coupling factors k p = 0.4, Curie temperature T C = 252 °C and the remanent polarization P r = 16.03 μC/cm2. These results show that (K, Na, Li) (Nb, Sb)O3 ceramics with small amount of Ta (x <8 mol%) are good lead-free piezoelectric ceramic.

Effect of La&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; on the Microstructure and Electrical Properties of 0.82Bi&lt;sub&gt;0.5&lt;/sub&gt;Na&lt;sub&gt;0.5&lt;/sub&gt;TiO&lt;sub&gt;3&lt;/sub&gt;-0.18Bi&lt;sub&gt;0.5&lt;/sub&gt;K&lt;sub&gt;0.5&lt;/sub&gt;TiO&lt;sub&gt;3&lt;/sub&gt; Ceramics

La2O3-doped lead-free 0.82Bi0.5Na0.5TiO3-0.18Bi0.5K0.5TiO3 (abbreviated to 0.82BNT-0.18BKT) piezoelectric ceramics were synthesized by the conventional mixed-oxide method, and the effect of La2O3 addition on the dielectric and piezoelectric properties was investigated. X-ray diffraction (XRD) patterns show that La2O3 diffuses into the lattice of the 0.82BNT-0.18BKT ceramics to form a solid solution with a pure perovskite structure. SEM images indicate that the grain size of the 0.82BNT-0.18BKT ceramics increased with the addition of La2O3 doping. The electrical properties of 0.82BNT-0.18BKT ceramics have been greatly improved by certain amount of La2O3 substitutions. At room temperature, the 0.82BNT-0.18BKT ceramics doped with 0.25 wt. % La2O3 exhibited the optimum properties with high piezoelectric constant (d33 = 142 pC/N) and high planar coupling factor (kp = 0.23).

Physical and Electrical Properties of Lead-Free (Bi&lt;sub&gt;0.5&lt;/sub&gt;Na&lt;sub&gt;0.5&lt;/sub&gt;)TiO&lt;sub&gt;3&lt;/sub&gt;–(Bi&lt;sub&gt;0.5&lt;/sub&gt;K&lt;sub&gt;0.5&lt;/sub&gt;)TiO&lt;sub&gt;3&lt;/sub&gt; Ceramics

Extending the investigations on (Bi0.5Na0.5)TiO3-based solid solution for lead-free piezoelectric ceramics, this paper consider the complex solid-solution system (Bi0.5Na0.5)TiO3–(Bi0.5K0.5)TiO3 [BNT-BKT]. (Bi0.5Na0.5)TiO3 with 7~ 30 mol% (Bi0.5K0.5)TiO3ceramics have been prepared following the conventional mixed oxide process. A morphotropic phase boundary (MPB) between rhombohedral (R) and tetragonal (T) was found at the composition 0.82BNT-0.18BKT with correspondingly enhanced piezoelectric properties. The electromechanical planar coupling factor is higher for compositions near the MPB. The mechanical quality factor (Qm), planar coupling coefficient (kp) and thickness coupling coefficient (kt) of 0.82BNT-0.18BKT ceramics were 125, 28.8% and 47.4%, respectively.

Low‐Temperature Sintering and Properties of 0.98PZT–0.02SKN Ceramics with LiBiO2 and CuO Addition

The low‐temperature sintering behavior of Pb(Zr0.53, Ti0.47)O3–Sr(K0.25, Nb0.75)O3 (PZT–SKN) piezoelectric ceramics with LiBiO2 and CuO addition has been investigated. The addition of 6 wt% LiBiO2 or 1 wt% LiBiO2+1 wt% CuO promotes the sinterability of 0.98PZT–0.02SKN ceramics owing to the generation of a liquid phase, resulting in a reduction of sintering temperature by about 300°–350°C. The microstructure, dielectric, and piezoelectric properties of flux‐sintered ceramics were examined and compared with materials conventionally sintered at 1250°C. PZT–SKN ceramics with 1 wt% LiBiO2+1 wt% CuO addition were sintered to high density at 900°C for 1 h. The resulting samples exhibited a high‐field d33 piezoelectric coefficient of 415 pm/V with a Curie temperature Tc of around 351°C, dielectric constant ɛr of 1235, and planar coupling factor kp of 0.54. The reduced sintering temperature and short soaking time, together with the favorable dielectric and piezoelectric properties of the fluxed PZT–SKN ceramics, demonstrate the potential opportunity of integration with low‐temperature cofired ceramic materials and low‐fire electrode materials for the multilayer piezoelectric transducer application.

Ferroelectric Properties of Bismuth-doped PMT-PT Ceramics

This study examined the ferroelectric properties of Bi-doped 0.66(Pb(1 3x/2)Bix)(Mg1/3Ta2/3)O30.34PbTiO3 ceramics for use as a piezoelectric transformer. The optimum conditions for obtaining samples with high density and improved electrical properties were a sintering temperature of 1200 C/4 h and the addition of 3 mol% Bi. The temperature dependent dielectric constant of the ceramics was examined at frequencies ranging from 1 kHz to 100 kHz. The broad dielectric constant anomaly coupled with a shift in the dielectric maximum towards higher temperature with increasing frequency indicates a relaxor-type behavior in the ceramics. The piezoelectric coecient (d 33) and the planar coupling factor (Kp) increase with the addition of 3 mol% Bi, and then decrease with further addition of Bi. The dielectric constant and the dissipation factor at room temperature could be improved by the addition of 3 mol% Bi.

Effects of Eu 2O 3 on the structure and electrical properties of 0.82Bi 0.5Na 0.5TiO 3–0.18Bi 0.5K 0.5TiO 3 lead-free piezoelectric ceramics

Eu 2O 3 (0–0.8 wt.%)-doped 0.82Bi 0.5Na 0.5TiO 3–0.18Bi 0.5K 0.5TiO 3 (BNKT18) lead-free piezoelectric ceramics were synthesized by conventional solid-state processes. The compositional dependence of phase structure and electrical properties of the BNKT18 ceramics was studied. X-ray diffraction (XRD) data shows that 0.2–0.8 wt.% Eu 2O 3 has diffused into the lattice of BNKT18 ceramics and forms a pure perovskite phase. SEM images indicate that the grain size of BNKT18 ceramics decreases with the increase of Eu 2O 3 content, and all the modified ceramics have a clear grain boundary and a uniformly distributed grain size. At room temperature, the ferroelectric and piezoelectric properties of the BNKT18 ceramics have been improved with the addition of Eu 2O 3, and the BNKT18 ceramics doped with 0.4 wt.% Eu 2O 3 have the highest piezoelectric constant ( d 33 = 145 pC/N), highest relative dielectric constant ( ε r = 1134) and lower dissipation factor (tan δ = 0.045) at a frequency of 10 kHz. The BNKT18 ceramics doped with 0.2 wt.% Eu 2O 3 have the highest planar coupling factor ( k p = 0.251). The temperature dependence of the relative dielectric constant shows T m increases with the addition of Eu 2O 3.

Piezoelectric, ferroelectric and dielectric properties of Sm 2O 3-doped (Bi 0.5Na 0.5) 0.94Ba 0.06TiO 3 lead-free ceramics

Sm 2O 3 (0–0.7 wt.%)-doped (Bi 0.5Na 0.5) 0.94Ba 0.06TiO 3 (abbreviated as BNBT6) lead-free piezoelectric ceramics were synthesized by conventional solid-state processes. The effects of Sm 2O 3 on the microstructure, dielectric properties and piezoelectric properties were investigated. X-ray diffraction (XRD) patterns show that 0.1–0.7 wt.% of Sm 2O 3 can diffuse into the lattice of BNBT6 ceramics forming pure perovskite phase. The SEM images indicate that the microstructure can be affected obviously by a small amount of added Sm 2O 3. The temperature dependence of the relative dielectric constant shows that Curie point decreases with the increase of Sm 2O 3. At room temperature, the ceramics doped with 0.3 wt.% Sm 2O 3 show quite good performance with excellent piezoelectric properties (piezoelectric constant d 33 of 202 pC N −1, planar coupling factor k p of 0.30 and mechanical quality factor Q m of 101) and improved dielectric properties (relative dielectric constant ɛ r of 2018 and dissipation factor tan δ of 0.056). Moreover, all BNBT6 − x (wt.%) Sm 2O 3 ceramics exhibit a typical relaxor behavior with diffuse phase transition characteristics and the degree of ferroelectric relaxation behavior is enhanced with the increase of Sm 2O 3 content.

Effect of Dy 2O 3 on the structure and electrical properties of (Bi 0.5Na 0.5) 0.94Ba 0.06TiO 3 lead-free piezoelectric ceramics

Dy 2O 3 (0–0.8 wt.%)-doped (Bi 0.5Na 0.5) 0.94Ba 0.06TiO 3 (abbreviated as BNBT6) lead-free piezoelectric ceramics were synthesized by conventional solid-state processes. The compositional dependence of phase structure and electrical properties of the ceramics was studied. X-ray diffraction (XRD) data shows that 0.2–0.8 wt.% Dy 2O 3 can diffuse into the lattice of BNBT6 ceramics and forms a pure perovskite phase. SEM images indicate that all the modified ceramics have a clear grain boundary and a uniformly distributed grain size, and the BNBT6 ceramics doped with appropriate Dy 2O 3 become denser. At room temperature, the ceramics doped with 0.6 wt.% Dy 2O 3 have the highest piezoelectric constant ( d 33 = 170 pC/N), higher mechanical quality factor ( Q m = 102), high relative dielectric constant ( ɛ r = 1611) and lower dissipation factor (tan δ = 0.051) at a frequency of 10 kHz. The BNBT6 ceramics doped with 0.4 wt.% Dy 2O 3 have the highest planar coupling factor ( k p = 0.33). Moreover, all BNBT6- x (wt.%) Dy 2O 3 ceramics exhibit a typical relaxor behavior with diffuse phase transition characteristics and the degree of ferroelectric relaxation behavior attains peak value at doping level of 0.4 wt.%.

The effect of (Li,Ce) doping in Aurivillius phase material (Na0.52K0.42Li0.06)0.5Bi2.5(Nb1.88Sb0.06Ta0.06)O9

AbstractThe effect of (Li,Ce) substitution for A‐site on the properties of [(Na0.52K0.42Li0.06)Bi]0.5Bi2 (Nb1.88Sb0.06Ta0.06)O9‐based ceramics was investigated. The piezoelectric activity of [(Na0.52K0.42Li0.06)Bi]0.5Bi2 (Nb1.88Sb0.06Ta0.06)O9‐based ceramics is significantly improved by the modification of lithium and cerium. The Curie temperature (TC) gradually decreases from 625 to 605 oC with increasing the (Li,Ce) modification. The piezoelectric coefficient d33 of the [(Na0.52K0.42Li0.06)Bi]0.44(Li,Ce)0.03[]0.03Bi2(Nb1.88Sb0.06Ta0.06)O9 ceramic was found to be 28 pC/N, the highest value among the [(Na0.52K0.42Li0.06)Bi]0.5Bi2(Nb1.88Sb0.06Ta0.06)O9‐based ceramics, also almost 50% higher than the reported d33 values of other Bismuth layer‐structured ferroelectric (BLSF) systems (∼5–19 pC/N). The planar coupling factor kp and kt were found to be 7.0 and 28.0%, together with the high TC (∼610 °C) and stable piezoelectric properties, demonstrating that the (Li,Ce) modified [(Na0.52K0.42Li0.06)Bi]0.5Bi2(Nb1.88Sb0.06Ta0.06)O9‐based material a promising candidate for high temperature applications.

Phase Characteristics and Piezoelectric Properties in the Bi0.5Na0.5TiO3–BaTiO3–K0.5Na0.5NbO3 System

Lead‐free 0.94Bi0.5Na0.5TiO3–(0.06−x)BaTiO3–xK0.5Na0.5NbO3 (x=0–0.06) ceramics were prepared. All these compositions have a structure close to the rhombohedral–tetragonal morphotropic phase boundary (MPB) and good electric properties at room temperature. No significant composition dependence of ferroelectric property can be established, whereas a dependence of piezoelectric properties can be observed, e.g. the piezoelectric coefficient (d33), planar coupling factor (kp), and field‐induced strain (S) increase with increasing x when x≤0.01 and then tend to decrease. The highest d33, kp, and bipolar strain are 118 pC/N, 0.29, and 0.32%, respectively, in the composition with x=0.01. The results not only indicate that BNT–BT–KNN lead‐free piezoceramics can persist in the structure close to MPB in a wide composition range but that they may also be helpful for further investigation on lead‐free piezoceramics.

Piezoelectric and dielectric properties of Sm 2O 3-doped 0.82Bi 0.5Na 0.5TiO 3–0.18Bi 0.5K 0.5TiO 3 ceramics

Sm 2O 3 (0–0.7 wt.%)-doped lead-free 0.82Bi 0.5Na 0.5TiO 3–0.18Bi 0.5K 0.5TiO 3 (abbreviated to 0.82BNT–0.18BKT) piezoelectric ceramics were synthesized by the conventional mixed-oxide method, and the effect of Sm 2O 3 addition on the dielectric and piezoelectric properties was investigated. X-ray diffraction (XRD) patterns show that Sm 2O 3 diffuses into the lattice of the 0.82BNT–0.18BKT ceramics to form a solid solution with a pure perovskite structure. SEM images indicate that the microstructure become uniform by doping a small amount of Sm 2O 3. The electrical properties of 0.82BNT–0.18BKT ceramics have been greatly improved by certain amount of Sm 2O 3 substitutions. At room temperature, the 0.82BNT–0.18BKT ceramics doped with 0.3 wt.% Sm 2O 3 exhibited the optimum properties with high piezoelectric constant ( d 33 = 147 pC/N) and high planar coupling factor ( k p = 22.4%).

Piezoelectric, ferroelectric and dielectric properties of Nd2O3-doped (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free ceramics

Abstract Nd 2 O 3 (0–0.8 wt.%)-doped (Bi 0.5 Na 0.5 ) 0.94 Ba 0.06 TiO 3 (abbreviated as BNBT6) lead-free piezoelectric ceramics were synthesized by conventional solid-state processes. The effects of Nd 2 O 3 on the microstructure, the dielectric, ferroelectric and piezoelectric properties were investigated. X-ray diffraction (XRD) data shows that Nd 2 O 3 in an amount of 0.2–0.8 wt.% can diffuse into the lattice of BNBT6 ceramics and form a pure perovskite phase. SEM images indicate that all the modified ceramics have a clear grain boundary and a uniformly distributed grain size, and the BNBT6 ceramics doped with Nd 2 O 3 become denser. The temperature dependence of the relative dielectric constant shows that Curie point does not change obviously with the addition of Nd 2 O 3 . At room temperature, the BNBT6 ceramics doped with 0.4 wt.% Nd 2 O 3 show quite good performance with excellent piezoelectric properties (piezoelectric constant d 33 of 175 pC/N, planar coupling factor k p of 0.31 and mechanical quality factor Q m of 118) and enhanced dielectric properties (relative dielectric constant ɛ r of 1947 and dissipation factor tan δ of 0.057). Moreover, all BNBT6 − x (wt.%) Nd 2 O 3 ceramics exhibit a typical relaxor behavior with diffuse phase transition characteristics.

Effect of Mn2O3 addition on the microstructure and electrical properties of lead-free (Na0.5K0.5)NbO3-Ba(Sn0.02Ti0.98)O3 ceramics

In this paper, the 0.98(Na0.5K0.5)NbO3–0.02Ba(Sn0.02Ti0.98)O3 ceramics with the addition of 0–4.0 wt % Mn2O3 have been prepared following the conventional mixed oxide process. The disc samples were sintered in alumina crucible at 1100°C for 3 h in air. For 0.98(Na0.5K0.5)NbO3–0.02Ba(Sn0.02Ti0.98)O3 ceramics, the electromechanical coupling coefficients of the planar mode kp and the thickness mode kt reach 0.31 and 0.39, respectively. In the low Mn2O3 content region (≤1 wt %), the decrease of dielectric constant, dielectric loss tangent and planar coupling factor together with the enhancement of mechanical quality factor correspond well to the feature of a hard doping effect on the electrical properties. For 0.98(Na0.5K0.5)NbO3–0.02Ba(Sn0.02Ti0.98)O3 ceramics by doping 1.0 wt % Mn2O3, the electromechanical coupling coefficients of the planar mode kp and the thickness mode kt reach 0.29 and 0.47, respectively, at the sintering of 1100°C for 3 h. The significant rise of dielectric loss tangent and degradation of mechanical quality factor in the high Mn2O3 content region (≥2 wt %) may be attributed to the appearance of distinct pores in the microstructure. With suitable Mn2O3 doping, a dense microstructure and good electrical properties were obtained.

A high temperature piezoelectric ceramic: (1-x)(Bi0.9La0.1)FeO3-xPbTiO3crystalline solutions

(1-x)(Bi(0.9)La(0.1))FeO(3-x)PbTiO(3) (BLF-PT) crystalline solutions for x = 0.35, 0.37, 0.4, 0.43 and 0.45 have been prepared by the solid-state reaction method. The X-ray diffraction analysis shows that BLF-PT has a single perovskite phase with mixed tetragonal and rhombohedral phases between x = 0.4 and 0.43. The Curie temperature of BLF-PT for x = 0.4 attains 460 degrees C, which is about 80 degrees C higher than that of hard Pb(Zr,Ti)O(3) ceramics. The remnant polarization and piezoelectric constant of BLF-PT for x = 0.4 reach 38 microC/cm(2) and 112 pC/N, respectively. The planar coupling factor k(p) of BLF-PT for x = 0.4 remains stable at temperature increases of up to 360 degrees C. The impedance spectroscopy study reveals that the high temperature conduction of BLF-PT may be attributed to the motion of oxygen vacancies within the material. Our results indicate that BLF-PT is a promising candidate for high temperature applications.

Structural and Electrical Properties of Lead-Free Ba(Sn,Ti)O3–(Na0.5K0.5)NbO3 Ceramics

(Na0.5K0.5)NbO3 with Ba(SnxTi1-x)O3 with x < 0.1 has been prepared by the conventional mixed oxide process. X-ray diffraction analysis revealed that, during sintering, all the Ba(SnxTi1-x)O3 diffuses into the lattice of (Na0.5K0.5)NbO3 to form a solid solution and the orthorhombic phase with a perovskite structure. The highest planar coupling factor of 0.98(Na0.5K0.5)NbO3–0.02Ba(Sn0.02Ti0.98)O3 ceramics is 0.31 after sintering at 1100 °C for 3 h. The samples with a low content of Ba(Sn0.06Ti0.94)O3 exhibit relatively good physical and electrical properties. For 0.98(Na0.5K0.5)NbO3–0.02Ba(Sn0.06Ti0.94)O3 ceramics, the electromechanical coupling coefficients of the planar mode kp and the thickness mode kt reach 0.18 and 0.46, respectively, after sintering at 1100 °C for 3 h. The ratio of the thickness coupling coefficient to the planar coupling coefficient is 2.56. With suitable Ba(SnxTi1-x)O3 concentration and sintering conditions, a dense microstructure and good electrical properties are obtained. Our results show that (Na0.5K0.5)NbO3–Ba(Sn0.06Ti0.94)O3 solid solution ceramics are promising lead-free ceramics for high-frequency electromechanical transducer applications.

Phase Transitions and Dielectric Properties in Bi(Zn1/2Ti1/2)O3–(Na1-yLiy)NbO3 Perovskite Solid Solutions

Perovskite solid solutions based on the system Bi(Zn1/2Ti1/2)O3–NaNbO3 were obtained via solid-state processing techniques. The crystal structure and ferroelectric phase transitions were studied by means of X-ray diffraction and dielectric measurements. A stable perovskite phase was obtained for Bi(Zn1/2Ti1/2)O3 substitutions up to 10 mol %. The dielectric characterization revealed that as the Bi(Zn1/2Ti1/2)O3 content increased, the transition temperature decreased and the transition peak became very diffuse. The polarization hysteresis loop and strain measurements presented evidence of an induced ferroelectric phase with 1 mol % Bi(Zn1/2Ti1/2)O3 substitutions. The planar coupling factor (kp) for 0.01Bi(Zn1/2Ti1/2)O3–0.99NaNbO3 was measured to be 0.28. In addition, with the substitution of Li for Na in the Bi(Zn1/2Ti1/2)O3–(Na1-yLiy)NbO3 system, the diffuseness of the transition peak decreased and the transition temperature increased.

Ultrahigh temperature Bi3Ti0.96Sc0.02Ta0.02NbO9-based piezoelectric ceramics

The effect of (Sc,Ta,Ce) doping on the properties of Bi3TiNbO9 (BTNO)-based ceramics was investigated. The cerium modification greatly improves the piezoelectric activity of Bi3(Ti0.96Sc0.02Ta0.02)NbO9-based ceramics and significantly decreases the dielectric dissipation. The d33 of Bi3Ti0.96Sc0.02Ta0.02NbO9+x wt %CeO2 (x=0.35) was found to be 18 pC/N, the highest value among the BTNO-based ceramics and almost three times as much as the reported d33 values of the pure BTNO ceramics (∼6 pC/N). The modification increased the resistivity ρ of the samples extremely, resolving the low resistivity problem for high temperature applications. The dielectric spectroscopy shows that the TC for all the ceramics is higher than 900 °C. The mechanical quality factor Q and planar coupling factors kp and kt of Bi3Ti0.96Sc0.02Ta0.02NbO9+0.35 wt %CeO2 ceramic were found to be 2835, 9%, and 23%, respectively, and it has high TC and stable piezoelectric properties, demonstrating that the (Sc,Ta,Ce) modified BTNO-based material is a wonderful candidate for high temperature applications.