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1.
《Ceramics International》2016,42(7):8438-8444
Comprehensive electrical properties of 0.94(Na1/2Bi1/2)TiO3–0.06BaTiO3 lead-free ceramics by doping series SrTiO3 were investigated. High piezoelectric constant of 205 pC/N and electromechanical coupling factor of 0.34 were obtained due to the forming of the rhombohedral–tetragonal morphotropic phase boundary at x=0.02–0.06. Very large recoverable strain of 0.34% was obtained at x=0.10 due to the coexistence of ferroelectric and relaxor pseudocubic phases. A large electrocaloric effect (ΔTmax=1.71 K and ΔT/ΔE=0.34 K mm kV−1 at 50 kV cm−1) which determined by indirect measurements method was obtained at 120 °C at x=0.02, which is significantly higher than that of lead-free ferroelectric ceramics reported so far. Moreover, lower operating temperatures of 50 °C and 30 °C were proposed when x=0.10 and 0.20 with ΔTmax=0.79 K and 0.6 K, respectively. These properties added together indicate a promising material for applications in cooling systems and actuators. 相似文献
2.
《Ceramics International》2016,42(5):6005-6009
Li2MnO3 ceramics co-doped with 2 wt% LiF and x wt% TiO2 (x=0, 3, 5, 7, 10) were prepared by solid-state reaction for low-temperature co-fired ceramics (LTCC) applications. The sintering temperatures of Li2MnO3 ceramics were successfully lowered to 925°C due to the formation of a LiF liquid phase. Their temperature stability was improved by doping with TiO2. A typical Li2MnO3-2 wt% LiF-5 wt% TiO2 sample with well-densified microstructures displayed optimum dielectric properties (εr=13.8, Q×f= 23,270 GHz, τf=1.2 ppm/°C). Such sample was compatible with Ag electrodes, which suggests suitability of the developed material for LTCC applications in wireless communication systems. 相似文献
3.
The effects of LiF addition on the sinterability and microwave dielectric properties of (Mg0.95Zn0.05)2(Ti0.8Sn0.2)O4 (MZTS) ceramics were investigated. A small amount of LiF addition can effectively lower the sintering temperature of MZTS from 1325 °C to 1150 °C due to the liquid phase effect and induce no apparent degradation of the microwave dielectric properties. With increasing LiF content, the apparent density and dielectric constant decreased gradually, the quality factor increased firstly and then decreased. In particular, MZTS–3.0 wt% LiF ceramics sintered at 1150 °C for 5 h exhibited good microwave dielectric properties of ?r = 13.05, Q · f = 119,310 GHz (at 10 GHz) and τf = ?59.2 ppm/°C. 相似文献
4.
The sintering properties and microwave dielectric properties of Ca[(Li1/3Nb2/3)1?xZr3x]O3+δ (x = 0.05, abbreviated as CLNZ) ceramic doped with ZBS frit are investigated for LTCC applications. XRD patterns and SEM photographs show that dense and single perovskite phase ceramics can be obtained with ZBS doping content of less than 10 wt%, before the Ca2Nb2O7 pyrochlore phase begins to segregates. The results show that ZBS vitreous phase stays at the grain boundary in the final sintered ceramics, suggesting it acts as liquid phase lubrication during sintering, and has effectively lowered the sintering temperature of CLNZ ceramics from 1170 °C to 940 °C. The preferred orientation of CLNZ solid solution varies from (1 2 1) plane to (1 0 1) plane as ZBS content and sintering temperature increase. The optimal microwave dielectric properties of ?r = 32.0, Qf = 6.64 THz and τf = ?27.1 ppm/°C can be obtained in 15 wt% ZBS doped CLNZ ceramic when sintered at 940 °C for 4 h. The Ag-cofiring experiment clearly shows that no chemical reaction takes place between Ag and the ZBS-doped CLNZ ceramic, indicating its great potential applications in LTCC field. 相似文献
5.
Dou Zhang Tim W. Button Vladimir O. Sherman Alexander K. Tagantsev Tim Price David Iddles 《Journal of the European Ceramic Society》2010,30(2):407-412
Commercial glass frits (lead borosilicate glasses) were employed as the sintering aids to reduce the sintering temperatures of BST ceramics. The effects of the glass content and the sintering temperature on the microstructures, dielectric properties and tunabilities of BST ceramics have been investigated. Densification of BST ceramics of 5 wt% glass content becomes significant from sintering temperature of 1000 °C. The glass content shows a strong influence on the Curie temperature Tc, permittivity and the diffuse transition. X-ray results show all BST ceramics exhibit a perovskite structure and also the formation of a secondary phase, Ba2TiSi2O8. The shift of BST diffraction peaks towards higher angle with increasing the glass content indicates the substitution of Pb2+ in Ba2+ site, which mainly accounts for the diffuse transition observed in these BST ceramics. BST ceramics with 10 wt% glass additives possess the highest tunability at all four sintering temperatures. A tunability of 12.2% at a bias field of 1 kV/mm was achieved for BST ceramics with 10 wt% glass content sintered at 900 °C. 相似文献
6.
《Ceramics International》2016,42(7):7962-7967
Y2O3 ceramics with good dielectric properties were prepared via co-precipitation reaction and subsequent sintering in a muffle furnace. The effects of Nd doping and sintering temperature on microwave dielectric properties were studied. With the increase in sintering temperature, the density, quality factor (Q×f), and dielectric constant (εr) values of pure Y2O3 ceramics increased to the maximum and then gradually decreased. The Y2O3 ceramics sintered at 1500 °C for 4 h showed optimal dielectric properties: εr=10.76, Q×f=82, 188 GHz, and τf=−54.4 ppm/°C. With the addition of Nd dopant, the Q×f values, εr, and τf of the Nd: Y2O3 ceramics apparently increased, but excessive amount degraded the quality factor. The Y2O3 ceramics with 2 at% Nd2O3 sintered at 1460 °C displayed good microwave dielectric properties: εr=10.4, Q×f=94, 149 GHz and τf=−46.2 ppm/°C. 相似文献
7.
《Ceramics International》2016,42(15):16644-16649
Ti-doped Sr0.9La0.1TiO3 ceramics with high density were successfully prepared in argon atmosphere by conventional solid state reaction. The influences of titanium doping content on the microstructure and thermoelectric properties were investigated. The results showed that titanium was oxidized during the calcination procedure. TiO2 phase survived and coexisted with Sr0.9La0.1TiO3 phase in the sintered ceramics. The Seebeck coefficients were increased from −163 to −259 μV/K as the temperature increased from 350 K to 1073 K. The thermal conductivity can be significantly reduced by doping Ti. Thermoelectric figure of merit (ZT) first decreased and then increased with increasing Ti doping content. Ceramics showed the best thermoelectric properties when Ti doping amount was 5 wt%, the maximum PF was 7.13 μW/K2/cm, and ZT value was 0.144 at 1073 K. 相似文献
8.
《Ceramics International》2016,42(16):18585-18591
Lead-free Ba0.85Ca0.15Zr0.10Ti0.90O3 (BCZT) ceramics were prepared by Plasma Activated Sintering (PAS). The influence of PAS sintering temperature on the crystalline phase, microstructure, and, dielectric and ferroelectric properties of BCZT ceramics were studied. The phase structure of BCZT ceramics first changed from rhombohedral phase to the coexistence of rhombohedral and tetragonal phases and then to tetragonal phase as the sintering temperature increased. Microstructural characterization of BCZT ceramics indicated that PAS can obtain a compact microstructure at lower temperatures of 1150–1300 °C compared with that from common pressureless sintering. The BCZT ceramics showed different degrees of diffuseness with increased temperature, and the diffuseness exponents C are all approximately on the order of 105 °C. The dielectric and ferroelectric properties of BCZT ceramics were enhanced with increased sintering temperature. BCZT ceramics sintered at 1250 °C exhibited optimum properties of room-temperature εr=2863, εm=6650, and 2Pr=25.24 μC/cm2, resulting from the relatively higher tetragonal phase content of the MPB between tetragonal and rhombohedral phases together with a compact microstructure. 相似文献
9.
《Ceramics International》2016,42(6):6993-7000
This paper reports the significant improved piezoelectric properties of high temperature bismuth titanate niobate (Bi3TiNbO9, BTN) polycrystalline ceramics. The piezoelectric performance of BTN ceramics is significantly enhanced by cerium modifications. The dielectric measurements indicate that the Curie temperature Tc gradually decreases over the temperature range of 907–889 °C with cerium contents increasing up to 0.7 wt%. The BTN-5Ce (BTN+0.5 wt% CeO2) exhibits optimized piezoelectric properties with a piezoelectric constant d33 of 16 pC/N, which is five times the value of unmodified BTN (d33~3 pC/N), while BTN-5Ce maintains a high Curie temperature Tc of 894 °C. The temperature-dependent electrical impedance and electromechanical coupling factors (kp, and kt) reveal that the BTN-5Ce exhibits thermally stable electromechanical coupling characteristics up to 500 °C but significantly deteriorates at 600 °C due to high conductivity at a higher temperature. The thermally stable electromechanical properties in combination with the ceramics׳ high electrical resistivity (106 Ω cm at 500 °C) and high Curie temperature (~900 °C) demonstrate that cerium-modified BTN ceramics are good materials for high temperature sensing applications. 相似文献
10.
《Journal of the European Ceramic Society》2007,27(8-9):3053-3057
The low sintering temperature and the good dielectric properties such as high dielectric constant (ɛr), high quality factor (Q × f) and small temperature coefficient of resonant frequency (τf) are required for the application of chip passive components in the wireless communication technologies. In the present study, the sintering behaviors and dielectric properties of Ba3Ti4Nb4O21 ceramics were investigated as a function of B2O3–CuO content. Ba3Ti4Nb4O21 ceramics with B2O3 or CuO addition could be sintered above 1100 °C. However, the additions of both B2O3 and CuO successfully reduced the sintering temperature of Ba3Ti4Nb4O21 ceramics from 1350 to 900 °C without detriment to the microwave dielectric properties. From the X-ray diffraction (XRD) studies, the sintering behaviors and the microwave dielectric properties of low-fired Ba3Ti4Nb4O21 ceramics were examined and discussed in the formation of the secondary phases. The Ba3Ti4Nb4O21 sample with 1 wt% B2O3 and 3 wt% CuO addition, sintered at 900 °C for 2 h, had the good dielectric properties: ɛr = 65, Q × f = 16,000 GHz and τf = 101 ppm/°C. 相似文献
11.
《Journal of the European Ceramic Society》2014,34(1):23-28
To assist the development of applications for multilayer piezoelectric devices, the low-temperature sintering piezoelectric ceramics of 0.3Pb(Zn1/3Nb2/3)O3-0.7Pb(Zr0.49Ti0.51)O3 with Li2CO3 and Sm2O3 additives were fabricated by a conventional solid-state reaction, and their structural and piezoelectric properties were studied. With the addition of Li2CO3, the minimum sintering temperature of 0.3Pb(Zn1/3Nb2/3)O3-0.7Pb(Zr0.49Ti0.51)O3 piezoelectric ceramics was reduced from 1125 °C to 950 °C through the formation of a liquid phase and its piezoelectric properties showed almost no degradation. When the sintering temperature was below 950 °C, however, the piezoelectric properties degraded obviously. The additional Sm2O3 resulted in a significant improvement in the piezoelectric properties of 0.3Pb(Zn1/3Nb2/3)O3-0.7Pb(Zr0.49Ti0.51)O3 ceramic with added Li2CO3. When sintered at 900 °C, the optimized properties of the 0.3Pb(Zn1/3Nb2/3)O3-0.7Pb(Zr0.49Ti0.51)O3 piezoelectric ceramic with 0.3 wt% Li2CO3 and 0.3 wt% Sm2O3 were obtained as d33 = 483 pC/N, k31 = 0.376, Qm = 73, ɛr = 2524, tan δ = 0.0178. 相似文献
12.
《Journal of the European Ceramic Society》2017,37(15):4653-4659
Different doping elements have been used to reduce the dielectric losses of CaCu3Ti4O12 ceramics, but their dielectric constants usually are undesirably decreased. This work intends to reduce their dielectric losses and simultaneously enhance their dielectric constants by co-doping Y3+ as a donor at A site and Al3+ as an acceptor at B site for substituting Ca2+ and Ti4+, respectively. Samples with different doping concentrations x = 0, 0.01, 0.02, 0.03, 0.05 and 0.07 have been prepared. It has been shown that their dielectric losses are generally reduced and their dielectric constants are simultaneously enhanced across the frequency range up to 1 MHz. The doped sample with x = 0.05 exhibits the highest dielectric constant, which is well over 104 for frequency up to 1 MHz and is about 20% higher than the undoped sample. Impedance spectra indicate that the doped samples have much higher grain boundary resistance than the undoped one. 相似文献
13.
《Ceramics International》2016,42(9):10758-10763
Large size Ba4.2Nd9.2Ti18O54 (BNT) ceramics doped with MnCO3, CuO and CoO were prepared by the conventional solid-state method. Only a single BaNd2Ti4O12 phase was formed in all samples. No second phase was found in the XRD patterns. The bulk density increases slightly because of the dopants. The SEM results showed that the grain size of Mn2+and Cu2+-doped BNT ceramics became larger with the increasing amount of dopants. The permittivity of all samples stays the same. However, the Q×f value of BNT ceramics increases by doping, especially with Mn2+ ions. The conductivity of BNT ceramic doped with Mn2+(0.5 mol‰) under high temperature is lower than that without doping. There are fewer defects in Mn2+-doped BNT ceramics. The XPS results indicated that Ti reduction was suppressed in BNT ceramics doped with 0.5 mol‰ Mn2+. BNT ceramics doped with 0.5 mol‰ Mn2+ ions sintered at 1320 °C for 2 h exhibited good microwave dielectric properties, with εr=88.67, Q×f=7408 GHz and τf = 82.98 ppm/°C. 相似文献
14.
The effects of Li2CO3–Bi2O3 (LB) additive on the microstructure, phase formation, microwave dielectric properties and applicability for low-temperature co-fired ceramics (LTCC) technology of (Ca0.9Mg0.1)SiO3 (CMS) ceramics were investigated. The sintering temperature of the CMS ceramics was reduced from 1290 °C to 890 °C by the addition of LB. Secondary phases SiO2 and Bi4(SiO4)3 were detected when LB content was less than 9 wt%. Low melting point liquid phases were formed when LB content was 11–14 wt%. The Qf value initially increased with the addition of LB and attained the maximum value for the 9 wt% LB-doped CMS ceramic. When the LB content exceeded 9 wt%, the Qf value decreased because of the presence of liquid phase and abnormal growth of grains. ?r of 6.92, Qf of 27,600 GHz and τf of ?43.6 ppm/°C were obtained for 9 wt% LB-doped CMS ceramics sintered at 890 °C for 2 h. Also the ceramics can be well co-fired with Ag electrode. 相似文献
15.
The anti-reduction of Ti4+ ions in Ba4.2Sm9.2Ti18O54 (BST) ceramics at high sintering temperature over 1300 °C was investigated. MgO, Al2O3 and MnO2 were added separately to suppress the reduction of Ti4+ ions so as to improve the microwave dielectric properties of BST ceramics. The microstructure of BST ceramics was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) was used to study the electroconductivity of BST ceramics and valency changes of Ti ions. The results showed that MgO or Al2O3, when acting as an acceptor, could effectively suppress the reduction of Ti4+ ions and significantly improve the Q × f values of BST ceramics at the cost of dielectric constant. Meanwhile, MnO2 as an oxidant had also improved the Q × f values but with no decrease in dielectric constant. Excellent microwave dielectric properties were achieved in Ba4.2Sm9.2Ti18O54 ceramics doped with 0.2 wt.% Al2O3 sintered at 1340 °C for 3 h: ?r = 76.9, Q × f = 10,120 GHz and τf = ?22.7 ppm/°C. 相似文献
16.
The (Mg0.93Ca0.05Zn0.02)(Ti1?xZrx)O3 ceramics were prepared by conventional solid-state route. The dielectric properties and structure of (Mg0.93Ca0.05Zn0.02)(Ti1?xZrx)O3 ceramics were investigated. It has been found that MgTiO3 and CaTiO3 are the main phases and a second phase CaZrTi2O7 appeared in 95MCT ceramics co-doped with Zn–Zr. With Zn–Zr additive, the sintering temperature of 95MCT ceramics can be reduced to 1300 °C, and adjust the temperature coefficient of dielectric constant. With the increasing of Zr content, dielectric constant ?r decrease from 22.6 to 19.91 and the temperature coefficient of dielectric constant αc from 5.93 to 2.52 ppm/°C when x = 0.01, 0.02, 0.03 and 0.04 mol respectively. The 95MCT ceramics with x = 0.02 has a dielectric constant ?r of 22.02, a dielectric loss of 2.78 × 10?4 and a temperature coefficient of dielectric constant αc value of 2.98 ppm/°C. 相似文献
17.
Yerang Cui Xinyu Liu Minhong Jiang Xiayan Zhao Xu Shan Wenhua Li Changlai Yuan Changrong Zhou 《Ceramics International》2012,38(6):4761-4764
Lead-free (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3–x%CeO2(BCZT–xCe) piezoelectric ceramics have been prepared by the traditional ceramic process and the effects of CeO2 addition on their phase structure and piezoelectric properties have been studied. The addition of CeO2 significantly improves the sinterability of BCZT ceramics which results in a reduction of sintering temperature from 1540 °C to 1350 °C without sacrificing the high piezoelectric properties. X-ray diffraction data show that CeO2 diffuses into the lattice of BCZT and a pure perovskite phase is formed. SEM images indicate that a small addition of CeO2 greatly affects the microstructure. Main piezoelectric parameters are optimized at around x = 0.04 wt% with a high piezoelectric coefficient (d33 = 600 pC/N), a planar electromechanical coefficient (kp = 51%), a high dielectric constant (?r = 4843) and a low dissipation factor (tan δ = 0.012) at 1 kHz, which indicates that the BCZT–xCe ceramics are promising for lead-free practical applications. 相似文献
18.
《Ceramics International》2017,43(18):16232-16237
In this paper, p-type Cu2O thin films have been epitaxially grown on n-type semiconducting (001) oriented Nb-SrTiO3 (NSTO) substrates with different Nb doping concentration by pulsed laser deposition technique. X-ray diffraction and high resolution transmission electron microscopy reveal a cube-on-cube epitaxial relationship between Cu2O and NSTO. It is found that the deposition temperature, the thickness of Cu2O films and the Nb doping concentration of NSTO substrates have critical impact on the photovoltaic (PV) properties of the Cu2O/NSTO heterojunction devices. A maximum PV performance is observed in ITO/Cu2O/NSTO device when the deposition temperature, film thickness and Nb doping concentration of NSTO are 550 °C, 76 nm, and 0.7 wt% NSTO, respectively. The optimized PV output corresponds to the open circuit voltage, short-circuit current density, fill factor and photovoltaic conversion efficiency about 0.45 V, 1.1 mA/cm2, 46% and 0.23%,respectively. This work offers an insight into the strategy for developing and designing novel optoelectronics of NSTO-based oxide heterostructures. 相似文献
19.
《Ceramics International》2016,42(6):7223-7229
CuO modified Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN–PMN–PT) ternary relaxor based ferroelectrics with the composition near the morphotropic phase boundary were synthesized by two-step columbite precursor method. The introduction of CuO significantly improved the sinterability of PIN–PMN–PT ceramics, resulting in the full densification of samples at lower sintering temperatures. It also profoundly modified the crystal structure and fracture mode of the ceramics. Properly increasing CuO content led to the disappearance of rhombohedral-tetragonal phase transition, remarkably improved the Curie temperature (Tc), and made the ceramics more relaxorlike. The ternary ceramics doped with 0.25 wt% CuO possessed optimum piezoelectric properties (d33=584 pC/N, d33*=948 pC/N, and kp=0.68), high ferroelectric properties (Ec=9.9 kV/cm, and Pr=33.1 μC/cm2), low dielectric loss (tan δ=0.9%), and wider temperature usage range (Tc=225 °C). The obtained properties are much higher than those of previously reported PIN–PMN–PT based ceramics, indicating that CuO doped PIN–PMN–PT is a promising candidate for electromechanical applications with high performance and wide temperature/electric field usage ranges. 相似文献
20.
《Ceramics International》2017,43(18):16167-16173
In this work, a series of low-temperature-firing (1−x)Mg2SiO4–xLi2TiO3–8 wt% LiF (x = 35–85 wt%) microwave dielectric ceramics was prepared through conventional solid state reaction. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses showed that the Li2TiO3 phase was transformed into cubic phase LiTiO2 phase and secondary phase Li2TiSiO5. Partial substitution of Mg2+ ions for Ti3+ ions or Li+Ti3+ ions increased the cell volume of the LiTiO2 phase. The dense microstructures were obtained in low Li2TiO3 content (x ≤ 65 wt%) samples sintered at 900 °C, whereas the small quantity of pores presented in high Li2TiO3 content (x ≥ 75 wt%) samples sintered at 900 °C and low Li2TiO3 content (x = 45 wt%) sintered at 850 and 950 °C. Samples at x = 45 wt% under sintering at 900 °C for 4 h showed excellent microwave dielectric properties of εr = 10.7, high Q × f = 237,400 GHz and near-zero τf = − 3.0 ppm/°C. The ceramic also exhibited excellent chemical compatibility with Ag. Thus, the fabricated material could be a possible candidate for low temperature co-fired ceramic (LTCC) applications. 相似文献