Piezoelectric characteristics of low temperature sintering Pb(Ni1/3Nb2/3)O3–Pb(Zr1/2Ti1/2)O3 ceramics as a function of Pb(Mn1/3Sb2/3)O3 substitution

In this study, in order to develop the composition ceramics for multilayer ceramic for ultrasonic nozzle and ultrasonic actuator application, Pb(Mn_1/3Sb_2/3)O₃ (abbreviated as PMS) substituted Pb(Ni_1/3Nb_2/3)O₃–Pb(Zr,Ti)O₃ (abbreviated as PNN-PZT) ceramics were fabricated using two-stage calcinations method and Li₂CO₃, Na₂CO₃ and ZnO as sintering aids, and their piezoelectric and dielectric characteristics were investigated. With the increase of the amount of PMS substitution, electromechanical coupling factor (k _p), and mechanical quality factor (Q _m) of specimens showed the maximum value at 3 mol% substituted specimen while dielectric constant (? _r) was decreased. At the sintering temperature of 900 °C, the density, ? _r, k _p, and Q _m of 3 mol% PMS substituted PNN-PZT composition ceramics showed the optimal values of 7.92 [g/cm³], 959, 0.584, and 1003, respectively, for low loss multilayer piezoelectric actuator application.     

Studies of resistivity and dielectric properties of magnesium doped barium titanate sintered in pure nitrogen

This paper investigated resistivity and dielectric properties of magnesium doped BaTiO₃. Influence of variable doping concentration and Ba/Ti ratio on densification, microstructure, resistivity and dielectric properties was studied. Ceramics sintered in pure nitrogen had higher apparent density than that of ceramics sintered in air. Second phase occurred when Mg doping concentration was greater than 2 mol%. Ceramics sintered in pure nitrogen had higher resistivity than ceramics sintered in air when A/B ratio ≥1. When Ba/Ti ratio was equal to 1.01, resistivity of the samples sintered in pure nitrogen increased with doping concentration increasing. Dielectric constant changed little with doping concentration increasing, but leakage conductivity decreased much. Samples with Ba/Ti ratio of 1.005 had the largest dielectric constant irrespective of doping concentration.     

Ferroelectricity of 30 nm BaTiO3 ceramics prepared by high pressure sintering

BaTiO₃ ceramics with a grain size of 30 nm were prepared at 6 GPa, 1,273 K using a three-step high pressure sintering method. The sintered bulk is uniform and the relative density is above 96% of the theoretical value. Similar to normal BaTiO₃, successive phase transitions were observed in 30 nm BaTiO₃ ceramics by X-ray diffraction method with the change of temperature. After annealing in O₂, a broadened ferroelectric transition was obtained at 398 K and the relative dielectric constant is 1,700 at 10 kHz.     

Effects of Al2O3 on the piezoelectric properties of Pb(Mn1/3Nb2/3)O3-PbZrO3-PbTiO3 ceramics

Piezoelectric properties of Al₂O₃-doped Pb(Mn_1/3Nb_2/3)O₃-PbZrO₃-PbTiO₃ ceramics were investigated. The constituent phases, microstructure, electromechanical coupling factor, dielectric constant, piezoelectric charge and voltage constants were analyzed. Diffraction peaks for (002) and (200) planes were identified by X-ray diffractometer for all the specimens doped with Al₂O₃. The highest sintered density of 7.8 g/cm³ was obtained for 0.2 wt% Al₂O₃-doped specimen. Grain size increased by doping Al₂O₃ up to 0.3 wt%, and it decreased by more doping. Electromechanical coupling factor, dielectric constant, piezoelectric charge and voltage constants increased by doping Al₂O₃ up to 0.2 wt%, and it decreased by more doping. This might result from the formation of oxygen vacancies due to defects in O^{2 −} ion sites and the substitution of Al³⁺ ions.     

Study on BaTiO3 semiconducting ceramic materials with lower resistivity

In this paper, the semiconducting mechanism of BaTiO₃ semiconducting ceramics with ABO₃ perovskite structure was investigated. The PTCR characteristics of BaTiO₃ semiconducting ceramic with lower resistivity have been studied by substituting in A position via doping with single donor Sb₂O₃, composite substituting in A and B position via doping with double donor Y₂O₃?+?Nb₂O₅, and substituting in oxygen position via doping with CaF₂ or TiCl₃.The results obtained show that lower resistivity and good PTC effect of BaTiO₃ semiconducting ceramics with room temperature resistivity (ρ ₂₅) of 6.08 Ω cm, temperature coefficient (α _T ) of 12.21?×?10^?2 °C^?1 and a lift–drag ratio (β) of 3.8?×?10⁴ can be achieved.     

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

(Na_0.47Bi_0.46Ba_0.06K_0.01)(Nb_0.02Ti_0.98-xZr_x)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.     

Application of spark plasma sintering for growing dense Pb(Mg1/3Nb2/3)O3–35 mol% PbTiO3 single crystal by solid-state crystal growth

This study examined the effect of spark plasma sintering (SPS) on the densification behavior and resulting dielectric and piezoelectric properties of Pb(Mg_1/3Nb_2/3)O₃–35 mol% PbTiO₃ ceramics with a 5 mol% excess of PbO. Through normal sintering at 1200^∘C, the density of the specimen reached only 92% of the theoretical density (TD). However, with the SPS treatment, the density of the PMN-PT ceramics increased to more than 99% of the TD at 900^∘C, and maintained over 98% of the TD during subsequent heat-treatment at 1200^∘C for 10 h. The increased density of the Pb(Mg_1/3Nb_2/3)O₃–35 mol% PbTiO₃ ceramics resulted in an improvement in the dielectric and piezoelectric properties. The SPS treatment was also successfully applied to the densification of a PMN-PT single crystal grown on a BaTiO₃ seed crystal using a solid-state crystal growth (SSCG) process.     

Effect of doped Ni2+ on the dielectric properties of NiO-BaTiO3 composites

NiO-BaTiO₃ composites were prepared by sintering BaTiO₃ together with NiO in air at 1300°C. Microstructure and morphology of the composites were detected by XRD and SEM, and the dielectric properties were measured by LCZ meter. The results indicate that the perovskite phase is formed in fact in status of solid solution doped with Ni²⁺, although only a small amount of Ni ions can dissolve into the perovskite phase. Ni doping decreases the formation temperature of the composite without inhibiting the grain growth of the crystalline phase. The dielectric constant decreases sharply and the dielectric loss decreases smoothly with increasing Ni²⁺ below NiO addition of 0.5 wt.%. When NiO addition increases above 0.5 wt.%, the dielectric constant and loss correlate with mixing rule of the two phases. Meanwhile, the replacement of Ni²⁺ for Ti⁴⁺ decreases the Curie temperature of perovskite phase by 30°C.     

Phase compositions and microwave dielectric properties of MgTiO<Subscript>3</Subscript>-based ceramics obtained by reaction-sintering method

MgTiO₃-based microwave dielectric ceramics were prepared successfully by reaction sintering method. The X-ray diffraction patterns of the sintered samples revealed a major phase of MgTiO₃-based and CaTiO₃ phases, accompanied with Mg₂TiO₄ or MgTi₂O₅ determined by the sintering temperature and time. The microwave dielectric properties had a strong dependence of sintering condition due to the different phase compositions and the microstructure characteristics. The ceramics sintered at 1360 °C for 4 h exhibited good microwave dielectric properties: a dielectric constant of 20.3, a high quality factor of 48,723 GHz (at 9GHz), and a temperature coefficient of resonant frequency of ?1.8 ppm/^oC. The obtained results demonstrated that the reaction-sintering process is a simple and effective method to prepare the MgTiO₃-based ceramics for microwave applications.     

Effects of strontium gallate additions on sintering behavior of gadolinia-doped ceria

The densification behavior and grain growth of Ce_0.8Gd_0.2O_1.9 ceramics were investigated with the strontium gallate concentration ranging from 0 to 5 mol%. Both the sintered density and grain size were found to increase rapidly up to 0.5 mol% Sr₂Ga₂O₅, and then to decrease with further addition. Dense Ce_0.8Gd_0.2O_1.9 ceramics with 97% of the theoretical density could be obtained for 0.5 mol% Sr₂Ga₂O₅-added specimen sintered at 1250^∘C for 5 h, whereas pure Ce_0.8Gd_0.2O_1.9 ceramics needed to be sintered at 1550^∘C in order to obtain an equivalent theoretical density. The addition of Sr₂Ga₂O₅ was found to promote the sintering properties of Gd₂O₃-doped CeO₂.     

Dielectric and piezoelectric properties of KCT added (Li0.02(Na0.56 K0.46)0.98(Nb0.81Ta0.15Sb0.04)O3 ceramics

In this study, [Li_0.02(Na_0.56 K_0.46)_0.98](Nb_0.81Ta_0.15Sb_0.04)O₃ + x mol% K_5.4Cu_1.3Ta₁₀O₂₉ ceramics were fabricated by conventional solid-state solution processes. Then, their dielectric and piezoelectric properties were investigated. Sinterability of all samples was enhanced because K_5.4Cu_1.3Ta₁₀O₂₉ (abbreviated as KCT) acted as sintering aids. As the result of XRD, phase structure showed orthorhombic symmetry when KCT ≤ 0.2 mol%. Whereas, the phase structure changed from orthorhombic symmetry to tetragonal symmetry when KCT?≥?0.4 mol%. The results suggest that the orthorhombic and tetragonal phases co-exist in the composition ceramics with 0.2 mol% < KCT < 0.4 mol% at room temperature. The effects of the addition of KCT on the dielectric and piezoelectric properties were investigated. As the result, excellent properties of density=4.81[g/cm³], electromechanical coupling factor (k_p)=0.48 and piezoelectric constant(d₃₃)=252[pC/N] were obtained in the composition ceramics with 0.4 mol%KCT.     

Ferroelectric and piezoelectric properties of tungsten doped CaBi4Ti4O15 ceramics

Tungsten doped CaBi₄Ti₄O₁₅ (CBT) ceramics was prepared by solid-state reaction method. A pure single phase of layer-structured ferroelectric with m?=?4 was formed when x?≤?0.025. The effect of W doping on dielectric, ferroelectric and piezoelectric properties was investigated. W⁶⁺ doping increased the temperature stability of dielectric constant and decreased dielectric loss. W⁶⁺ doping decreased the remanent polarization, while the coercive field decreased as well, as a result, the piezoelectric constant was increased. AC conductivity measurement showed that W⁶⁺ doping increased the conductivity of CBT ceramics and showed n-type conducting mechanism. W⁶⁺ doped ceramics has smaller activation energy due to many defects introduced in the crystal lattice.     

Investigation of the BaTiO3–BaMg1/3Nb2/3O3 system: Structural, dielectric, ferroelectric and electromechanical studies

Lead-free (1?x) BaTiO₃ –x BaMg_1/3Nb_2/3O₃ ceramics with x?=?0.03, 0.04, 0.05 and 0.06 were prepared by solid-state synthesis. The effects of the Ba(Mg_1/3Nb_2/3)O₃ addition on the phase composition, dielectric and ferroelectric properties, as well as the electromechanical response of the classic ferroelectric BaTiO₃ were investigated. The room-temperature X-ray diffraction analyses of all the ceramics revealed a perovskite phase after sintering at 1300 °C with a composition-dependent symmetry. The samples with a lower concentration of Ba(Mg_1/3Nb_2/3)O₃, i.e., x?=?0.03 and 0.04, were tetragonal, while the samples with x?=?0.05 and 0.06 were found to be cubic. The result is in agreement with the dielectric, ferroelectric and electromechanical properties. With x increasing from 0.03 to 0.06 the temperature of the diffused maximum of the dielectric permittivity decreased from 348 K to 265 K. All the ceramics showed a large electromechanical response: the calculated room-temperature electrostrictive coefficient M ₃₃ of the sample with x?=?0.06 was 1.4 · 10^?16?m²/V², which is comparable to the value measured for Pb(Mg_1/3Nb_2/3)O₃ ceramics.     

Piezoelectric and dielectric characteristics of low temperature sintering Pb(Ni1/3Nb2/3)O3-Pb(Mn1/3Nb2/3)O3-Pb(Zr1/2Ti1/2)O3 ceramics for multilayer piezoelectric actuator

In this study, in order to develop the composition ceramics for multilayer piezoelectric actuator, PNN substituted PMN-PZT ceramics were fabricated using Li₂CO₃ and Na₂CO₃ as sintering aids, and their piezoelectric and dielectric characteristics were investigated. With the increase of the amount of PNN substitution, dielectric constant (εr), electromechanical coupling factor (k _p), and piezoelectric constant (d ₃₃) of specimens showed the maximum value at each sintering temperature, and crystal structure changed from tetragonal to rhombohedral. At the sintering temperature of 950^∘C, the density, εr, k _p, d ₃₃, Q_m and Tc of 12 mol% PNN substituted PMN-PNN-PZT composition ceramics showed the optimal values of 7.79 g/cm³, 1160, 0.599, 419pC/N, 894 and 332^∘C, respectively, for low loss multilayer piezoelectric actuator application.     

Effects of various oxide fillers on physical and dielectric properties of calcium aluminoborosilicate-based dielectrics

Physical and dielectric properties of LTCC (low temperature co-fired ceramics) materials based on a typical calcium aluminoborosilicate glass and various fillers such as Al₂O₃, BaTiO₃, CaTiO₃, TiO₂, ZrO₂, MgO and SiO₂ were investigated. Densification, crystallization and thermal and dielectric properties were found to strongly depend on the type of filler. The XRD patterns of Al₂O₃, BaTiO₃, CaTiO₃ and MgO samples demonstrated crystalline phases, CaAl₂Si₂O₈, BaAl₂Si₂O₈, CaTiSiO₅ and CaMgSi₂O₆, respectively, as a result of firing at 850 °C. For the sample containing CaTiO₃ filler, specifically, dielectric constant increased drastically to approximately 19.9. A high quality factor of >210 and a high TCE (temperature coefficient of expansion) of >8.5 ppm/°C were obtained for the composition containing MgO or SiO₂. Near zero TCF (temperature coefficient of frequency) was obtained for the samples containing TiO₂. The purpose of this work is to investigate the effects of various ceramic fillers on physical and dielectric properties and ultimately to provide the technical guidelines for the proper choice of filler in various LTCC systems.     

Electrical characterization of TiO2-based ceramics for VOCs

Cr doped TiO₂ and TiO₂/Cr₂O₃ powders are prepared by sol–gel technique and solid state reaction respectively. The structural and electronic properties of these powders are investigated. The responses of the materials made from the powders to benzene and formaldehyde vapors are studied. The research results show that Cr³⁺ can enter into the lattice as substitutional metal dopant by sol gel route at lower temperature. The segregation of Cr₂O₃ happens when Cr content exceed 8 at.%. The resistance of TiO₂ can be remarkable decreased by doping Cr³⁺ as substitutional metal dopant. Besides Cr³⁺, the segregation of Cr₂O₃ also contributes to the alteration of conduction from n- to p-type. With some other catalyzer, both of Cr doped TiO₂-based and Cr₂O₃/TiO₂-based ceramics can detect benzene and formaldehyde vapors at 21 ppm.     

Low temperature sintering of high performance KNN-based lead-free piezoelectric ceramic using BCBM frit as sintering aid

High performance lead-free (K_0.49Na_0.51)_0.98Li_0.02(Nb_0.77Ta_0.18Sb_0.05)O₃?+?0.5 mol%BaZrO₃ piezoelectric ceramic was selected as base material, while BaO-CuO-B₂O₃-MnO₂ frit was used as sintering aid to lower the sintering temperature. The effect of BaO-CuO-B₂O₃-MnO₂ frit doping amount on the sintering behavior, structure and electrical properties of the ceramics was investigated. The optimal sintering temperature of the ceramics decreased with the increase of frit doping amount. The ceramic with frit doping amount of 1.0 wt.%, sintered at a reduced temperature of 1100°C, exhibited optimal electrical properties as follows: piezoelectric constant d ₃₃?=?345 pC/N, planar electromechanical coupling coefficient k _p?=?44.5 %, mechanical quality factor Q _m?=?135, dielectric constant ε ₃₃ ^T ?=?1210, and dielectric loss tanδ?=?0.018. Together with its relatively high T _c?=?195°C, this ceramic was an excellent candidate for replacing the lead-based piezoceramics in practical applications.     

Donor-Acceptor Charge Complex Formation in Barium Titanate Ceramics: Role of Firing Atmosphere

BaTiO₃ ceramics containing Mn acceptors and various Mo, W and Nb donor dopants have been fired in reducing atmosphere and re-oxidized in N₂/O₂. In single Mn-doped ceramics, Mn²⁺ is completely oxidized to Mn³⁺; in N₂ containing 50 ppm O₂ at T > 800°C. Changes of the Curie point and sample length under reduction and re-oxidation have been detected using dielectric and thermomechanical measurements. Charge compensation and complex formation between acceptors and donors have been observed. In donor-acceptor charge complexes, Mn²⁺ cannot be oxidized.     

Microstructural and piezoelectric properties of PZN substituted PMN-PZT ceramics for multilayer piezoelectric transformer

In this paper, in order to develop the low temperature sintering ceramics for multilayer piezoelectric transformers, Pb[(Mn_1/3,Nb_2/3)_0.07(Zn_1/3Nb_2/3)_a (Zr_0.48Ti_0.52)_1-0.07-aO₃] ceramics were prepared with the variations of PZN from 2 to 14 mol% and their dielectric and piezoelectric properties were investigated. Sintering temperature was varied from 940 to 1000^∘C. At 8 mol% PZN substituted specimen sintered at 970^∘C, electromechanical coupling factor(kp), mechanical quality factor(Qm), dielectric constant and peizoelectric constant(d₃₃) showed the optimal values of 0.536, 1803, 1551 and 328[pC/N], respectively, for multilayer piezoelectric transformer application.     

Phase transition and electrical studies of wolframium doped SrBi2Ta2O9 ferroelectric ceramics

In this study, crystalline structure, dielectric and impedance properties of SrBi₂Ta₂O₉ (SBT) - based ferroelectric ceramics have been investigated with the substitution of wolframium/tungsten (W) onto the tantalum site. Wolframium doped SrBi₂(W _x Ta_{1 − x} )₂O₉ (0.0 ≤ x ≤ 0.20) ceramics were synthesized by solid state reaction method. The X-ray diffractogram analysis revealed that the substitution formed a single phase layered perovskite structure for the doping content up to x ≤ 0.05. The dielectric measurements as a function of temperature show an increase in Curie temperature (T _c ) over the composition range of x = 0.05 to 0.20. The W^{6 +} substitution in perovskite-like units results in a sharp dielectric anomaly at the ferroelectric phase transition. Furthermore, the dielectric constant at their respective Curie temperature increases with wolframium doping. Both enhanced Curie temperatures and dielectric constants at the Curie points indicate an increase in polarizability, which could be attributed to the increased “rattling space” due to the incorporation of the smaller tungsten cations. The dielectric loss reduces significantly with tungsten addition. AC impedance properties vis-à-vis wolframium content has also been studied.