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1.
Optical transmittance and crystal-lattice distortion and their relation were studied in hot-pressed La-doped Pb zirconate-titanate (PLZT) ferroelectric ceramics at the ferroelectric-antiferroelectric morphotropic phase boundary. In the thermally annealed condition, the crystal system of PLZT at the FE-AFE morphotropic phase boundary was pseudotetragonal and similar to the antiferroelectric phase (AFEβ ) appearing in Pb(Zr, Ti)O3 and (Pb, Sr)ZrO3 . Optical transmittance and crystal-lattice distortion change monotonically with respect to the Zr/Ti ratio, and the optical transmittance increases approximately linearly with decreasing lattice distortion. In view of these relations and the temperature dependence of the optical transmittance, it is suggested that light scattering in PLZT ceramics is caused mainly by the variation in refractive index encountered as the light travels from one domain or grain into another. 相似文献
2.
Ping Sun Chao-Nan Xu Morito Akiyama Tadahiko Watanabe 《Journal of the American Ceramic Society》1999,82(6):1447-1450
Transparent PLZT(7/60/40) ceramics with large piezoelectric coefficients were obtained using a two-step sintering process with controlled oxygen partial pressure. Specifically, low-oxygen-pressure and low-temperature sintering were used in the first step, followed by a high-oxygen-pressure, high-temperature sintering cycle. High-density ceramics with small grain sizes of about 3 µm were prepared. As a result, k p = 0.71, k 33 = 0.78, d 33 = 850 × 10-12 C/N, and a transparency of 15% (λ= 610 nm, thickness of 1 mm) have been achieved; 20% improvement of d 33 was gained compared to conventional processed PLZT ceramics ( d 33 = 710 × 10-12 C/N). 相似文献
3.
GALEB H. MAHER 《Journal of the American Ceramic Society》1983,66(6):408-413
Additions of small amounts of silver to a PLZT dielectric with emphasis on the 88/12/70/30, Pb/La/Zr/Ti, composition were investigated. It was found that a few mole percent of Ag1+ could be incorporated into the PLZT lattice as a large acceptor cation and that it tended to reduce the lead vacancies, which are normally generated by the substitution of La3+ in the PLZT dielectric. The addition, up to 2 mol% of silver, decreased the 25°C dielectric constant from 2300 to 1700. However, the temperature coefficient of capacitance was improved to ±5% between -55° and +125°C, and the dissipation factor was reduced from 1.5 to 0.5%. Although the gravimetrically measured lead loss appeared to depend on the relative vapor pressure of lead oxide during sintering, the compensation mechanism of Ag1+ was not affected. 相似文献
4.
Using a novel combustion method, Eu-doped Eu:yttrium aluminum garnet (YAG) and Eu:YSAG powders, and transparent Eu:YSAG ceramics were fabricated. The optical properties of these transparent ceramics have been measured, and a reduced peak splitting of Eu3+ for 5 D0 →7 F1 and 5 D0 →7 F2 was observed when 10 at.% Al3+ was substituted by Sc3+ . The enhanced symmetry of the Eu sites in YAG lattice, which resulted from the expanded YSAG lattice by Sc3+ doping, is the main reason for the reduced peak splitting. 相似文献
5.
Lanthanum-doped lead zirconate-titanate ferroelectric ceramics (PLZT) were tested acoustically using the pulse-echo technique at 20 MHz. Phase transitions occurring within the range –269° to 300°C were detected in poled and unpoled Pb1.02- x Lax (Zr0.65 Ti0.35 )O3 with x =0.00 to 0.15. For x =0.00 to 0.08 a phase transition observed between 0° and 100°C was defined by changes in the longitudinal sound velocity as great as 5% accompanied by pronounced absorption peaks. Measurements of resonance and electromechanical coupling in poled samples indicate that this transition involves 2 ferroelectric phases. The acoustic techniques reported made possible the detection of the subtler phase transitions in PLZT ceramics with a degree of sensitivity much higher than that available from the more conventional techniques. Both poled and unpoled samples may be tested by this technique, so that the influence of domain orientation on the transitions observed can be demonstrated. 相似文献
6.
Ferroelectric and Photostrictive Properties of Fine-Grained PLZT Ceramics Derived from Mechanical Alloying 总被引:2,自引:1,他引:1
Kenta Takagi Shoko Kikuchi Jing-Feng Li Hiroshi Okamura Ryuzo Watanabe Akira Kawasaki 《Journal of the American Ceramic Society》2004,87(8):1477-1482
Single-phase lead lanthanum zirconate titanate (PLZT) solid solution powder was synthesized from the constituent oxides at ambient temperature through a mechanical alloying (MA) process and was then densified to fine-grained ceramics by sintering and hot-pressing. The anomalous photovoltaic effect (APV) and photoinduced strain of the resultant PLZT ceramics were investigated and analyzed in association with the influence of grain size. It was found that a photoinduced voltage up to 6000 V·cm−1 can be obtained as the grain size is reduced to 0.42 μm. This is extremely high and about three times that achievable in normal micrometer-grained PLZT ceramics. The maximum photoinduced strain of the PLZT ceramics with an average grain diameter of 0.54 μm reached 0.01%, which is equivalent to electric-field-induced strain of common piezoelectric materials. 相似文献
7.
S. S. N. Bharadwaja T. Dechakupt S. Trolier-McKinstry H. Beratan 《Journal of the American Ceramic Society》2008,91(5):1580-1585
A KrF pulsed excimer laser (248 nm) was utilized to crystallize sputtered La-modified Pb(Zr,Ti)O3 (3:30:70) (PLZT) films on LaNiO3 -coated silicon substrates. The film surface was irradiated with defocused laser pulses in an oxygen ambient at various substrate temperatures. Polycrystalline, phase pure perovskite PLZT thin films were produced for substrate temperatures of 250°C and higher. The dielectric constant and loss tangent values of laser-assisted crystallized (10 min exposure at 10 Hz using a substrate temperature of 400°C) PLZT thin films at 10 kHz were 406 and 0.027; in comparison, rapid thermal annealed films (annealed at 700°C for 1 min) showed values of 400 and 0.021, respectively. Laser crystallized films exhibited a remanent polarization value of 14 μC/cm2 with a coercive field |( E +c + E −c )|/2 of 95 kV/cm. 相似文献
8.
Sodium-rich NASOCON-type ceramics, the NaM2 (PO4 )3 +y Na2 O (M = Ge, Ti, Hf, Zr) system, were investigated in order to obtain a material having a high Na+ conductivity and high density. The ionic conductivity and the sinterability were greately improved by an increase in the valve of y for all of the system examined. Added Na2 O was not souble in teh NASICON-type skeletton, sice the lattice constants and teh X-ray diffraction patterns were not changed by the Na2 O addintion in all of the samples. Na2 O acts as a flux for obtaining highly dense ceramics and highly conductive grain boundaries. Partial A2 site insertion by Na+ ions is effective for the enhancement of conductivity, because the conductivity for Na1.5 M(III)0.5 Zr1.5 (PO4 )3 (M = In or Y) is about 1 order of magnitude higher than the maximum conductivity of the NaZr2 (PO4 )3 +y Na2 O system. 相似文献
9.
Wen-Jen Lin Tseung-Yuen Tseng Sheuan-Perng Lin Shun-Lih Tu Hong Chang Sheng-Jenn Yang I-Nan Lin 《Journal of the American Ceramic Society》1997,80(5):1065-1072
Lead lanthanum zirconate titanate (Pb1− x La x (Zr y ,Ti z )O3 , PLZT) films containing [00 l ] preferentially oriented grains were produced successfully on YBa2 Cu3 O7− x -coated (YBCOcoated) SrTiO3 (STO) or YBCO/CeO2 -coated silicon substrates; films containing randomly oriented grains were created on platinum-coated silicon substrates. The latter possessed significantly inferior ferroelectric properties, a fact ascribed to the presence of a paraelectric phase (TiO2 ) at the PLZT/platinum interface. On the other hand, the PLZT/YBCO/STO films exhibited better electrical properties than did the PLZT/YBCO/CeO2 /Si films, and this phenomenon was attributed to better alignment of the grains in normal and in-plane orientations. In terms of fatigue properties, the [00l] textured films that were deposited on YBCO/CeO2 /Si substrates possessed substantially superior polarization-switching-cycle endurance versus the randomly oriented films grown on Pt(Ti)/Si substrates. Moreover, the tetragonal films behaved much more satisfactorily than did the rhombohedral PLZT films. The ferroelectric parameters of tetragonal PLZT films showed no significant degradation up to 109 polarization switching cycles, whereas the remnant polarization and coercive force of the rhombohedral PLZT films had already degraded to 80% of their initial values after 108 cycles. 相似文献
10.
Kouichi Harada Hideyuki Kanai Yohachi Yamashita 《Journal of the American Ceramic Society》1996,79(8):2109-2112
An aging model for relaxors is suggested on the basis of the transformation of a supercooled cubic lattice into a tetragonal lattice. Manganese ions distort the crystal lattice, and the distortion affects the phase transformation rate. As a result, the aging rate may be expected to change. The lattice constant of (Pb0.63 Ba0.37 )(Zr0.7 Ti0.3 )O3 +χ MnO mol% dielectric ceramics was used as a measure of the degree of the distortion. As the lattice constant decreased up to 0.5 MnO mol%, the aging rate increased, justifying the proposed model. 相似文献
11.
Shingo Hirano Masaru Yoshinaka Ken Hirota Osamu Yamaguchi 《Journal of the American Ceramic Society》1996,79(1):171-176
In the ZrO2 -Cr2 O3 system, metastable t -ZrO2 solid solutions containing up to 11 mol% Cr2 O3 crystallize at low temperatures from amorphous materials prepared by the hydrazine method. The lattice parameter c decreases linearly from 0.5149 to 0.5077 nm with increased Cr2 O3 content, whereas the lattice parameter a is a constant value ( a = 0.5077 nm) regardless of the starting composition. At higher temperatures, transformation (decomposition) of the solid solutions proceeds in the following way: t (ss)→ t (ss) + m + Cr2 O3 → m + Cr2 O3 . Above 11 mol% Cr2 O3 addition, c-ZrO2 phases are formed in the presence of Cr2 O3 . The t -ZrO2 solid solution powders have been characterized for particle size, shape, and surface area. They consist of very fine particles (15–30 nm) showing thin platelike morphology. Dense ZrO2 (3Y)-Cr2 O3 composite ceramics (∼99.7% of theoretical) with an average grain size of 0.3 μm have been fabricated by hot isostatic pressing for 2 h at 1400°C and 196 MPa. Their fracture toughness increases with increased Cr2 O3 content. The highest K Ic value of 9.5 MPa·;m1/2 is achieved in the composite ceramics containing 10 mol% Cr2 O3 . 相似文献
12.
TOSHIAKI MURAKAMI TADASHI MIYASHITA MOTOHIRO NAKAHARA EIJI SEKINE 《Journal of the American Ceramic Society》1973,56(6):294-297
Lattice constants, grain size, electrical conductivity, and luminescence were measured for sintered BaTiO3 ceramics doped with 0 to 1.2 at.% rare-earth ions. BaTiO3 doped with low levels of rare-earth ions contains grains 10 μm in size and has lattice constants nearly equal to those of undoped ceramics. In this case, rare-earth ions occupy Ba2+ sites and yield donors. When grain growth is inhibited by high doping levels or by insufficient sintering, the lattice constants change, the rare-earth ions occupy both Ba2+ and Ti4+ sites, and, consequently, BaTiO3 becomes insulative because of charge compensation. 相似文献
13.
Effects of Grain Size and Porosity on Electrical and Optical Properties of PLZT Ceramics 总被引:2,自引:1,他引:1
A group of transparent ferroelectric hot-pressed (Pb0.92 La0.08 )-(Zr0.65 Ti0.35 )0.98 O3 specimens with controlled grain size and constant porosity and a group of similar specimens with controlled porosity and constant grain size were prepared. The electrical and optical constants and polarization-reversal properties of these ceramics were determined as functions of grain size and porosity. When poled PLZT ceramics were aged, the polarization-reversal characteristic was quite asymmetric, apparently because a space-charge field, E8p , was generated during aging. From a detailed study of the behavior of the E8p , including its (1) generation with increasing aging time, (2) relaxation with repeated polarization reversals, (3) relaxation by heat depolarization, and (4) grain-size and porosity dependence, it is concluded that the space-charge layer is present inside every domain. This layer also explains the grain-size dependencies of the remanent polarization, piezoelectric constants, and Curie point. 相似文献
14.
Dielectric properties of A(B3+ 1/2 B5+ 1/2 )O3 (A = Ba, Ca, Sr; B3+ = La, Nd, Sm, Yb; B5+ = Nb, Ta) ceramics have been investigated at microwave frequencies. Sr(B3+ 1/2 B5+ 1/2 )O3 and Ca(B3+ 1/2 B5+ 1/2 )O3 ceramics have relative dielectric constants (ε r ) above 20 and negative temperature coefficients of resonant frequency (T f ). In the group of Ba(B3+ 1/2 B5+ 1/2 )O3 ceramics, T f changes from + 118 ppm/° to nearly zero according to the kinds of B-site ions. Among the ceramics investigated, Sr(Sm1/2 Ta1/2 )O3 ceramics have the highest Q values at microwave frequencies. For Sr(Sm1/2 Ta1/2 )O3 ceramics Q = 7000, ε r = 27.7, and T f =−62.5 ppm/° at 8.5 GHz. The microstructure of Sr(Sm1/2 Ta1/2 )O3 ceramics is composed of a matrix of the ternary compound (Sr-Sm-Ta-O system) and secondary phase grains of the binary compound (Sm-Ta-O system). 相似文献
15.
William L. Warren Bruce A. Tuttle E. Christopher Rong Gary J. Gerardi Edward H. Poindexter 《Journal of the American Ceramic Society》1997,80(3):680-684
The nature of extrinsic point defects in lead zirconate titanate (PZT) ceramics of various compositions prepared by solution chemistry has been explored. Using electron paramagnetic resonance (EPR), several impurity sites have been identified in the as-received materials, which include Fe3+ oxygen vacancy (VO ‥ ) complex and isolated Cu2+ ions; both of these ions are incorporated into the lattice by replacing the Ti(Zr) ion. A Fe3+ VO ‥ complex serves as a sensitive probe of the local crystalline field environment of the ceramic; the symmetry of this defect is roughly correlated with its phase diagram as the composition is varied from PbTiO3 to PbZrO3 . The Fe3+ VO ‥ complex experiences tetragonal, rhombic, or orthorhombic symmetry as the composition is varied from PbTiO3 to PbZrO3 . As the composition of the Cu2+ ion is varied, it appears as though the addition of Zr, and not necessarily a change in phase, is largely responsible in determining the local environment of this acceptor impurity. Also, the Cu2+ resonance parameters weakly reflect the relative Ti–O(Zr–O) bond covalency in the perovskite lattice. 相似文献
16.
Thermal expansion behaviors of Ba6−3 x Ln8+2 x Ti18 O54 (Ln=La, Nd, and Sm, x =0.5, 0.67, and 0.75) ceramics were determined by dilatometric measurement. The samples of all investigated compositions expanded nearly linearly with increasing temperature in the range of 20°–1200°C. Their thermal expansion coefficients were determined to be 10.7–11.4 ppm/°C. A discontinuous change in sample size was observed at about 1350°C for each composition, indicating the existence of a phase transition. As determined by the high-resolution X-ray diffraction analysis, the phase constitution and the lattice parameters of Ba6−3 x Sm8+2 x Ti18 O54 ceramics were maintained in the quenched samples. The origin of the phase transition was discussed thoroughly. Phase equilibrium in the BaTiO3 –Ln2/3 TiO3 system was reviewed by considering the phase transition. 相似文献
17.
Kyu Hyoung Lee Yi Feng Wang Sung Wng Kim Hiromichi Ohta Kunihito Koumoto 《International Journal of Applied Ceramic Technology》2007,4(4):326-331
We report herein on Ruddlesden–Popper-type doped Sr n +1 Ti n O3 n +1 ( n =2) as a potential candidate for n -type thermoelectric (TE) oxides. The TE properties of 5 at.% La-, Nd-, and Nb-doped Sr3 Ti2 O7 polycrystalline ceramics were investigated and the origin of Seebeck coefficient was discussed from the viewpoint of the symmetry of TiO6 octahedra. A significant reduction in the lattice thermal conductivity was observed by the enhancement of phonon scattering at SrO/(SrTiO3 ) n interfaces originating from the inherent superlattice structure, and the maximum dimensionless figure of merit, ZT ∼0.15, at a 1000 K value was obtained in 5 at.% La-doped Sr3 Ti2 O7 . 相似文献
18.
Preparation, Structure, and Properties of Thermally and Mechanically Improved Aluminum Titanate Ceramics Doped with Alkali Feldspar 总被引:3,自引:0,他引:3
Masahide Takahashi Masahiro Fukuda Masaaki Fukuda Hisato Fukuda Toshinobu Yoko 《Journal of the American Ceramic Society》2002,85(12):3025-3030
Aluminum titanate (AT) ceramic materials doped with alkali feldspar ((Na0.6 K0.4 )AlSi3 O8 ) have been prepared. These ceramics exhibited high sinterability, large resistance to thermal decomposition, and large flexure strength. The existence of liquid-phase feldspar at sintering temperatures promoted the formation of AT ceramics as the sintering agent. It was considered that silicon ions substituting for aluminum ions at the surface of AT crystal grains lowered the surface energy and hindered the diffusion of Ti4+ and Al3+ , giving rise to the large resistance to thermal decomposition. As a result, doping with alkali feldspar was found to effectively improve the mechanical and thermal properties of AT ceramics. 相似文献
19.
E. C. SUBBARAO 《Journal of the American Ceramic Society》1960,43(3):119-122
Dielectric, lattice constant, and thermal-expansion measurements have been made on solid solution ceramics in the systems PbTiO3 Pb0.5 NbO3 and PbTiO3 -Pbo.5 TaO3 . The ferro-electric Curie temperature is lowered to 465OC. at the solubility limit (2 to 5% Nb or Ta). Replacement of Ti4+ by Nb5+ or Ta5+ in these perovskite-type solid solutions is accompanied by the creation of cation vacancies. These vacancies seem to facilitate material transport and aid sintering. Thus ceramics were obtained with up to 91% of theoretical density. These compositions have peak dielectric constants of the order of 10,000 with tan δ less than 0.1 in the interval 25° to 525°C. 相似文献
20.
Yunfei Chang Zupei Yang Lirong Xiong Zonghuai Liu Zenglin Wang 《Journal of the American Ceramic Society》2008,91(7):2211-2216
Lead-free (K0.44 Na0.52 Li0.04 )(Nb0.80− x Ta0.20 Sb x )O3 piezoelectric ceramics were prepared by the ordinary sintering method. The much higher Pauling electronegativity of Sb compared with Nb makes the ceramics more covalent. By increasing x from 0.00 to 0.06, the phase structure of the ceramics changed from the tetragonal to the pseudocubic phase, and both the bands in the Raman scattering spectra shifted to lower frequency numbers. The grain growth of the ceramics was improved by substituting Sb5+ for Nb5+ . By increasing x , the dielectric properties were optimized and the variation of dielectric constants before and after poling became smaller. Only the tetragonal–cubic phase transition was observed above room temperature in all the ɛr – T curves. The degree of diffuseness increased from 1.29 at x =0.00 to 1.96 at x =0.06, indicating that the ceramics at x =0.06 changed to an approximate ideal relaxor ferroelectric. The temperature dependences of f r and k p became better by increasing x properly. Significantly, the ceramics with x between 0.00 and 0.04 had high density and outstanding electrical properties ( d 33 =241–272pC/N, k p =0.42–0.52, ɛr =1258–1591, tan δ=0.015–0.025, T c =280°–355°C, E c =10.62–12.60 kV/cm, and P r =16.19–20.13 μC/cm2 ). Besides, the underlying mechanism for variations of the electrical properties due to Sb5+ substitution was explained in this work. 相似文献