Planar Mode Electromechanical Coupling Factor Research Articles

Structure and enhanced electrical properties of high-temperature BiFeO3-PbTiO3-BaZrO3 ceramics with bismuth excess

0.54BiFeO3–0.36PbTiO3–0.1BaZrO3 (BF-PT-BZ) ceramics with various amounts of excess Bi were fabricated by conventional solid-state method and the microstructure and electrical properties were researched to estimate the role of excess Bi on the structure and properties in sintering process. XRD results indicate that tetragonal distortion declined monotonously with the increasing amount of Bi. SEM images reflect that the grain size was enlarged by excess Bi addition. The dielectric, ferroelectric and piezoelectric properties of BF-PT-BZ ceramics were improved effectively. Remnant polarization Pr, piezoelectric coefficient d33 and planar mode electromechanical coupling factor kp of BF-PT-BZ ceramics with 1 mol% Bi excess are 20 μC/cm2, 197 pC/N and 0.448, improved by 20%, 30% and 39%, respectively. The temperature of the maximum dielectric constant Tm of 445 °C for BF-PT-BZ-1 mol% Bi shows tremendous potential for high temperature piezoelectric applications.

Fabrication by Annealing at Approximately 1030°C and Electrical Characterization of Lead-Free (1 − x)Bi0.5K0.5TiO3–xBa(Fe0.5Nb0.5)0.05Ti0.95O3 Piezoelectric Ceramics

Sintered (1 − x)Bi0.5K0.5TiO3–xBa(Fe0.5Nb0.5)0.05Ti0.95O3 [(1 − x)BKT–xBFNT] piezoelectric ceramics have been fabricated by conventional annealing at 1000°C to 1050°C. X-ray diffraction (XRD) analysis revealed that the 0.9BKT–0.1BFNT ceramic sintered at 1030°C showed high transition temperature of TC = 514°C due to presence of Bi4Ti3O12 in solid solution. Although the P–E ferroelectric loop was not yet saturated, the remanent polarization and coercive electric field of the 0.9BKT–0.1BFNT showed good values of Pr = 18.5 μC/cm2 and Ec = 4.3 kV/cm, respectively. The piezoelectric parameters of the ceramic included planar-mode electromechanical coupling factor of kp = 0.17 and mechanical quality factor of Qm = 145, larger than the values of 0.17 and 57, respectively, obtained for BKT ceramic.

Li-modified Ba0.99Ca0.01Zr0.02Ti0.98O3 lead-free ceramics with highly improved piezoelectricity

In this paper, Ba0.99Ca0.01Zr0.02Ti0.98O3 lead-free ceramics with highly enhanced piezoelectricity have been obtained at an optimized Li+ ion doping content by means of elaborately adjusting the microstructure. The introduction of Li+ ions significantly improves the sinterability due to the emergence of oxygen vacancies and the formation of eutectic liquid phase. The sintering temperature is reduced by 100–150 °C compared with other literatures. The highest piezoelectric coefficient d33 and planar mode electromechanical coupling factor kp can be increased up to 340 pC/N and 44%, which are stem from outstanding ferroelectric activity (Pr = 9.8 μC/cm2, Ec = 220 V/mm) and dielectric property (εr = 2250, tan δ = 1.35%). In addition, the Curie temperature Tc is still maintained about 120 °C. A plausible mechanism concerning the defect dipoles, polarization rotation, and ferroelectric phase transition is constructed in this work to well state above mentioned phenomena.

Effects of cobalt and sintering temperature on electrical properties of Ba0.98Ca0.02Zr0.02Ti0.98O3 lead-free ceramics

Lead-free (Ba0.98Ca0.02)(Zr0.02Ti0.98)O3-xmol% (x = 0–1.6) cobalt ceramics (BCZT-xCo) have been fabricated by the traditional solid-state reaction technique and the effects of Co and sintering temperature on ferroelectric, dielectric and piezoelectric properties of (Ba0.98Ca0.02)(Zr0.02Ti0.98)O3 lead-free ceramics have been studied systematically. The orthorhombic–tetragonal (T O–T) transition shift towards lower temperature with increasing Co addition, while Curie temperature (T c) remained at relatively high value of 107 °C. And the Main piezoelectric parameters are optimized at x = 0.8 mol% with a high piezoelectric coefficient (d 33 = 330 pC/N), a planar mode electromechanical coupling factor (k p = 46.7 %), a high dielectric constant (e r = 2,675) and a low dielectric loss (tanδ = 0.90 %) at 1kHZ. Besides these, high remnant polarization (P r) and low coercive field (E c) of 11.5 μC/cm2, 0.31 kV/cm are also obtained at (Ba0.98Ca0.02)(Zr0.02Ti0.98)O3-0.8 mol%Co lead-free ceramics. Furthermore, greatly enhanced temperature stability of the piezoelectric properties was obtained in the temperature range from 20 to 90 °C. The above results indicate that BCZT-Co ceramics are promising lead-free materials for practical applications.

Sintering and electrical properties of La-modified (Na0.52K0.45Li0.03)1−3xLax(Nb0.88Sb0.09Ta0.03)O3 lead-free ceramics

(Na0.52K0.45Li0.03)1−3xLax(Nb0.88Sb0.09Ta0.03)O3 (NKLLxNST) lead-free ceramics were prepared by normal sintering and their dielectric and piezoelectric properties were investigated. The X-ray methods indicate that the NKLLxNST ceramics with x≤0.003 present a pure perovskite phase at room temperature. The bulk density of NKLLxNST ceramics increases with proper amount of La2O3 contents, and reaches its highest value of 4.544g/cm3 with the addition of 0.3mol% La2O3. At x=0.003, remnant polarization Pr, piezoelectric constant d33 and planar mode electromechanical coupling factor kp of NKLLxNST ceramics reach the highest values of 37.80μC/cm2, 346pC/N and 40%, respectively, exhibiting excellent “soft” piezoelectric characteristics, demonstrating a tremendous potential of the compositions studied for device applications.

Polymorphic phase transition and enhanced piezoelectric properties in (Ba0.9Ca0.1)(Ti1−xSnx)O3 lead-free ceramics

Lead-free (Ba0.9Ca0.1)(Ti1−xSnx)O3 (BCTS) (x=0.02–0.1) ceramics were fabricated using conventional solid state reaction method. The effects of Sn substitution on structure and electrical properties of the BCTS ceramics were researched. At room temperature, a polymorphic phase transition (PPT) from tetragonal phase to rhombohedral phase is identified from XRD patterns with increasing Sn content. High piezoelectric coefficient of d33=405pC/N and planar mode electromechanical coupling factor of kp=43.2% are obtained for the sample at x=0.06. The ceramic for x=0.06 also shows uniform microstructure that contributes to the excellent electrical properties. These results indicate that this BCTS system with optimal composition is a promising lead-free piezoelectric material.

Structure and piezoelectric properties of Cu-doped potassium sodium tantalate niobate ceramics

The Cu-doped (K 0.5Na 0.5)(Nb 0.95Ta 0.05)O 3 (KNNT) ceramics were prepared by the solid state reaction ceramic technique. The phase structure and the micro-morphology were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). There exhibits a single phase in perovskite structure, even the grain sizes increase with copper addition. The dielectric constant ( ε), the planar mode electromechanical coupling factor ( k p), the piezoelectric coefficient ( d 33), and the mechanical quality factor ( Q m) of KNNT ceramics with copper additive are 320–450, 0.21–0.41, 70–110 pC/N, 105–979, respectively.

Sintering and Electrical Properties of Lead‐Free Na0.5K0.5NbO3 Piezoelectric Ceramics

Lead‐free Na0.5K0.5NbO3 (NKN) piezoelectric ceramics were fairly well densified at a relatively low temperature under atmospheric conditions. A relative density of 96%–99% can be achieved by either using high‐energy attrition milling or adding 1 mol% oxide additives. It is suggested that ultra‐fine starting powders by active milling or oxygen vacancies and even liquid phases from B‐site oxide additives mainly lead to improved sintering. Not only were dielectric properties influenced by oxide additives, such as the Curie temperature (Tc) and dielectric loss (D), but also the ferroelectricity was modified. A relatively large remanent polarization was produced, ranging from 16 μC/cm2 for pure NKN to 23 μC/cm2 for ZnO‐added NKN samples. The following dielectric and piezoelectric properties were obtained: relative permittivity ɛT33/ɛ0=570–650, planar mode electromechanical coupling factor, kp=32%–44%, and piezoelectric strain constant, d33=92–117 pC/N.

Synthesis and Characterization of (K0.5Na0.5)(Nb0.7Ta0.3)O3 Piezoelectric Ceramics Sintered with Sintering Aid K5.4Cu1.3Ta10O29

The sinterability and electrical properties of (K0.5Na0.5)(Nb0.7Ta0.3)O3 ceramics were investigated as functions of K5.4Cu1.3Ta10O29 (KCT) sintering aid content. The (K0.5Na0.5)(Nb0.7Ta0.3)O3 ceramics showed a perovskite single phase and a high density at KCT contents ranging from 0.23 to 0.38 mol %. In this composition range, the electrical properties of (K0.5Na0.5)(Nb0.7Ta0.3)O3 ceramics were also improved. The planar-mode electromechanical coupling factor (kp) of (K0.5Na0.5)(Nb0.7Ta0.3)O3 ceramics reached 0.44–0.46 in this KCT content range. A high mechanical quality factor (Qm) of 680 was obtained at a 0.23 mol % KCT content. The (K0.5Na0.5)(Nb0.7Ta0.3)O3 ceramics prepared with 0.23 mol % KCT exhibited a field-induced strain of 0.11% at 40 kV/cm and a piezoelectric constant d33 of 270 pm/V.

Sinterability and Piezoelectric Properties of (K,Na)NbO3 Ceramics with Novel Sintering Aid

Dense (K,Na)NbO3 (KNN)-based ceramics were developed by optimizing the sintering conditions with newly developed K4CuNb8O23 (KCN) as a sintering aid. The sinterability and electrical properties of KNN ceramics were investigated as a function of KCN concentration. The density of KNN ceramics increased monotonically with increasing the KCN contents, and reached the highest value of 4.40 g/cm3 with the addition of 0.5 mol% KCN. This is due to the formation of liquid phase, which significantly promotes the densification of KNN ceramics. The Curie temperature (Tc) of pure KNN ceramics was 420°C and decreased with increasing the KCN content. With the addition of 0.5 mol% KCN, planar mode electromechanical coupling factor (kp) and mechanical quality factor (Qm) of KNN ceramics also reached the highest values of 0.39 and 1200, respectively. The KNN ceramics prepared with 0.5 mol% KCN exhibited a large field-induced strain of 0.09% at 40 kV/cm and the piezoelectric constant d33 of 180 pm/V.