共查询到20条相似文献,搜索用时 31 毫秒
1.
Junji Awaka Norihito Kijima Yasuhiko Takahashi Hiroshi Hayakawa Junji Akimoto 《Solid State Ionics》2009,180(6-8):602-606
High-purity specimens of Li6CaLa2Ta2O12 and Li6BaLa2Ta2O12 have been successfully synthesized by solid-state reactions. The analytical chemical compositions of these samples were in good agreement with the nominal compositions of Li6CaLa2Ta2O12 and Li6BaLa2Ta2O12. The Rietveld refinements verified that these compounds have the garnet-type framework structure with the lattice constants of a = 12.725(2) Å for Li6CaLa2Ta2O12 and a = 13.001(4) Å for Li6BaLa2Ta2O12. All of the diffraction peaks of X-ray powder diffraction patterns were well indexed on the basis of cubic symmetry with space group Ia-3d. To make a search for Li sites, the electron density distributions were precisely examined by using the maximum entropy method. Li+ ions occupy partially two types of crystallographic site in these compounds: (i) tetrahedral 24d sites, and (ii) distorted octahedral 96h sites, the latter of which are the vacant sites of the ideal garnet-type structure. The present Li6CaLa2Ta2O12 and Li6BaLa2Ta2O12 samples exhibit the conductivity σ = 2.2 × 10? 6 S cm? 1 at 27 °C (Ea = 0.50 eV) and σ = 1.3 × 10? 5 S cm? 1 at 25 °C (Ea = 0.44 eV), respectively. 相似文献
2.
《Solid State Ionics》2006,177(26-32):2363-2368
The mechanism and kinetics of water incorporation in the double perovskites Ва4Ca2Nb2O11 and Sr6Ta2O11 has been investigated (T = 300÷500 °C and aH2O = 1 · 10− 3÷2.2 · 10− 2). The formation of hydration products Ba4Ca2Nb2O11·xH2O and Sr6Ta2O11·xH2O (0.2 < x < 0.50) was limited by the diffusion of H2O. It has been found that the concentration dependences of D˜H2O are the same for both samples: small increasing of D˜H2O with increasing x. The temperature dependences of the chemical diffusion coefficients of water for compositions of Ba4Ca2Nb2O11·0.35H2O and Sr6Ta2O11·0.35H2O could be described with close activation energies of Ea = 0.38 ± 0.03 eV and Ea = 0.49 ± 0.03 eV, respectively. The chemical diffusion coefficients of water are nearly one order of magnitude smaller for tantalate Sr6Ta2O11. This result correlates with lower oxygen and proton conductivities in Sr6Ta2O11 as the consequence of lower mobilities. 相似文献
3.
《Solid State Ionics》2006,177(19-25):1879-1881
The double ordered perovskites NdBaCo2O5 and NdBaCo2O6 were prepared by soft chemistry. The samples were characterized from a structural and chemical point of view, concomitantly with their physical properties. Upon reduction, NdBaCo2O5 is formed with a tetragonal unit cell (a = b = 3.94 Å, c = 7.57 Å) and presents an antiferromagnetic behavior. Upon oxidation, a complete stoichiometric ordered phase NdBaCo2O6 with a tetragonal unit cell (a = b = 3.88 Å, c = 7.63 Å) could be obtained with a ferromagnetic and a metallic behavior. Finally it is shown that these phases are able to reversibly catch and release oxygen, suggesting a high anionic conductivity. 相似文献
4.
《Current Applied Physics》2009,9(5):1046-1053
Multilayer bandpass and bandstop filters have been produced using electron beam evaporation. Initially bandstop filter is modeled with non absorbing zinc sulphide (ZnS) and zinc selenide (ZnSe). When the absorption data was incorporated for the said materials significant absorption was observed at shorter wavelengths of the spectral band restricting the practical usage of the filter. ZnS and ZnSe were then replaced by dispersive silicon dioxide (SiO2), tantalum penta oxide (Ta2O5) and titanium dioxide (TiO2) along with their absorption and the filters are optimized to get desired bandpass and bandstop data. Bandpass and bandstop filters with desired performance were experimentally characterized with two combinations SiO2/Ta2O5/glass and SiO2/TiO2/glass. The measured average transmission for both combination (bandpass) in the pass band was about 92% with T < 1% in the stop band. Slightly narrow bandwidth was observed for SiO2/TiO2/glass as compared to SiO2/Ta2O5/glass which is attributed to layers densification. Similarly Tavg ⩾ 80% was achieved for two combinations of bandstop filters with T < 0.1% in the stop band. The structure and surface morphology of the prepared filters were characterized by X-ray diffraction and scanning electron microscopy. XRD analysis reveals amorphous structure. SEM analysis also reveals that the layers are compact and have good surface quality. 相似文献
5.
Choon-W. Nahm 《Journal of Physics and Chemistry of Solids》2012,73(7):834-838
The effect of Ta2O5 addition on microstructure, electrical properties, and dielectric characteristics of the quaternary ZnO–V2O5–MnO2 vaistor ceramics was investigated. Analysis of the microstructure indicated that the quaternary ZnO–V2O5–MnO2–Ta2O5 ceramics consisted of mainly ZnO grain and minor secondary phases such as Zn3(VO4)2, ZnV2O4, TaVO5, and Ta2O5. As the amount of Ta2O5 increased, the sintered density increased from 94.8 to 97.2% of the theoretical density (5.78 g/cm3 for ZnO), whereas the average grain size decreased from 7.7 to 6.0 μm. The ceramics added with 0.05 mol% Ta2O5 exhibited the highest breakdown field (2715 V/cm) and the highest nonlinear coefficient (20). However, further increase caused α to abruptly decrease. The Ta2O5 acted as a donor due to the increase of electron concentration in accordance with the amount of Ta2O5. The donor concentration increased from 1.97×1018 to 3.04×1018cm?3 with increasing the amount of Ta2O5 and the barrier height exhibited the maximum value (0.95 eV) at 0.05 mol% Ta2O5. 相似文献
6.
《Current Applied Physics》2007,7(2):124-134
Thermal stabilities of various metal bottom electrodes were examined by using a Ta2O5 metal-oxide-metal (MOM) capacitor structure. After depositing 10-nm thick Ta2O5 on metal-electrode/poly-Si, we performed rapid thermal oxidation (RTO) at 850 °C for 60 s in an O2 ambient. A chemical-vapor-deposition (CVD) WSi2 electrode showed satisfactory thermal stability after the RTO, while other examined electrode materials exhibited thermal degradation caused by oxidation failure or interfacial reaction between the substrate poly-Si and the Ta2O5. After post-annealing at 650 °C for 30 min (in N2 condition) with CVD TiN top electrode, an effective oxide thickness (Tox) of ∼32 Å and a leakage current density of ∼107 A/cm2 at 1.25 V were obtained from the MOM capacitor with the WSi2 bottom electrode. Other electrode materials, such as TiN, TiSix, WNx, W, and Ta, were severely oxidized during the RTO in the MOM structures, and very poor capacitor properties were obtained in terms of Tox and leakage current. 相似文献
7.
G. Liu W. Wong-Ng J.A. Kaduk L.P. Cook 《Physica C: Superconductivity and its Applications》2010,470(5-6):345-351
Chemical interactions between the Ba2YCu3O6+x superconductor and the LaMnO3 buffer layers employed in coated conductors have been investigated experimentally by determining the phases formed in the Ba2YCu3O6+x–LaMnO3 system. The Ba2YCu3O6+x–LaMnO3 join within the BaO–(Y2O3–La2O3)–MnO2–CuOx multi-component system is non-binary. At 810 °C (pO2 = 100 Pa) and at 950 °C in purified air, four phases are consistently present along the join, namely, Ba2?x(La1+x?yYy)Cu3O6+z, Ba(Y2?xLax)CuO5, (La1?xYx)MnO3, (La,Y)Mn2O5. The crystal chemistry and crystallography of Ba(Y2?xLax)CuO5 and (La1?xYx)Mn2O5 were studied using the X-ray Rietveld refinement technique. The Y-rich and La-rich solid solution limits for Ba(Y2?xLax)CuO5 are Ba(Y1.8La0.2)CuO5 and Ba(Y0.1La1.9)CuO5, respectively. The structure of Ba(Y1.8La0.2)CuO5 is Pnma (No. 62), a = 12.2161(5) Å, b = 5.6690(2) Å, c = 7.1468(3) Å, V = 494.94(4) Å3, and Dx = 6.29 g cm?3. YMn2O5 and LaMn2O5 do not form solid solution at 810 °C (pO2 = 100 Pa) or at 950 °C (in air). The structure of YMn2O5 was confirmed to be Pbam (No. 55), a = 7.27832(14) Å, b = 8.46707(14) Å, c = 5.66495(10) Å, and V = 349.108(14) Å3. A reference X-ray pattern was prepared for YMn2O5. 相似文献
8.
The electrical properties and the mechanism of lithium ionic diffusion in the Li7La3Ta2O13 compounds were investigated. The bulk and total conductivity at 300 K of the Li7La3Ta2O13 compound are about 3.3 × 10? 6 S/cm and 2.6 × 10? 6 S/cm, respectively. The activation energy of bulk and total conductivity is in the range of 0.38–0.4 eV. A prominent internal friction peak in Li7La3Ta2O13 compounds was observed around 280 K at 0.5 Hz, which is actually composed of two subpeaks (P1 peak at lower temperature and P2 peak at higher temperature). From the shift of peak position with frequency, the activation energy of 1.0 eV and the pre-exponential factor of relaxation time in the order of 10? 18–10? 21 s were obtained if one assumes Debye relaxation processes. These values of relaxation parameters strongly suggest the existence of interaction between the relaxation species (here lithium ions or vacancies). Based on the coupling model, the relaxation activation energies are deduced as 0.45 eV and the pre-exponential factor of relaxation time as 10? 15 s. Judging from these relaxation parameters and the similarity of structure between Li7La3Ta2O13 and Li5La3Ta2O12 compounds, the P1 and P2 peaks are suggested to be related with the lithium ionic diffusion between 48g?48g and 24d?48g. 相似文献
9.
Kunimitsu Kataoka Yasuhiko Takahashi Norihito Kijima Hiroshi Hayakawa Junji Akimoto Ken-ichi Ohshima 《Solid State Ionics》2009,180(6-8):631-635
Single crystals of Li4 + xTi5O12 were prepared by means of electrochemical Li-ion intercalation technique using parent Li4Ti5O12 single crystals. The obtained Li4 + xTi5O12 (x = 1.35) crystallizes in the cubic spinel-related type structure, space group Fd3?m, and lattice parameters of a = 8.346(2) Å and V = 581.3(5) Å3 and Z = 8. The Li-ion intercalated sites were successfully determined to be both the 8a and 16c sites by using the difference Fourier synthesis map. The structure was determined by single-crystal X-ray structure analysis and refined to the conventional value of R = 3.7% for 132 independent observed reflections. The chemical composition has been determined to be Li5.35Ti5O12 from the result of site-population refinements. In addition, theoretical electron density distributions and total energy were calculated for three postulated compounds of “Li4.5Ti4.5O12” and “Li4.5 + xTi4.5O12” with x = 1.5 and 3.0. 相似文献
10.
Toshinori Okura Mitsugu Saimaru Hideki Monma Kimihiro Yamasita 《Solid State Ionics》2009,180(6-8):537-540
Glass-ceramics of the titanium-, germanium- or tellurium-containing Na5RSi4O12-type (R = rare earth; Y) Na+-superionic conductors (N5YXS) were prepared by crystallization of glasses with the composition Na3+3xY1 ? xXySi3 ? yO9 (X = Ti; NYTiS, Ge; NYGeS, X = Te; NYTeS), and the effects of X elements on the separation of the phase and the microstructural effects on the conduction properties of glass-ceramics were discussed. The combination of x and y was most varied in N5YGeS and more limited in the order of N5YTeS > N5YTiS. Their conductivities and activation energies are of the order of 10? 2 S/cm at 300 °C and of 15 to 24 kJ/mol, respectively. The conductivity of the glass-ceramic N5YXS decreases giving the order N5YGeS > N5YTeS > N5YTiS. It is considered that this order corresponds to the N5 single phase region. Large enhancement of electrical conductivity was observed in the glass-ceramics as the grain growth was promoted with increase of heating temperature and heating time for crystallization. 相似文献
11.
《Superlattices and Microstructures》1998,24(5):381-384
Four atom states Cu3dx2 − y2, Cu4s, Oa2pxare involved in a tight-binding model for the superconducting CuO2plane. The orthorhombic distortion is taken into account by the differences of Cu–O hopping amplitudes and single-site oxygen energies εaand εbof two oxygen positions in the elementary cell as well. An effective ‘oxygen’ Hamiltonian including only the electron amplitudes at the oxygen ions is derived. Simple expressions for the constant energy contours and the Fermi surface are obtained and they qualitatively describe the photoemission spectra. Extended saddle points nearp = (π,0) andp = (0,π) are observed in qualitative agreement with the ARPES data. The van Hove singularities of the density of states (DOS) related to the extended saddle points are calculated by a Monte Carlo method. It is found that the splitting of the singularity of the DOS at the bottom of the conduction band is created by the energy difference εa − εb = 2δ. 相似文献
12.
A. Mizoguchi T. Yagi K. Kondo T.O. Sato H. Kanamori 《Journal of Quantitative Spectroscopy & Radiative Transfer》2012,113(4):279-285
The N2 and O2 pressure broadening coefficients of the pure rotational transitions at 625.66 GHz (NKaKc=101?9–100?10, J=10.5–10.5) and 649.70 GHz (NKaKc=102?9–92?8, J=9.5–8.5) in the vibronic ground state X2A′ of the perhydroxyl (HO2) radical have been determined by precise laboratory measurements. For the production of HO2, the mercury-photosensitized reaction of the H2 and O2 precursors was used to provide an optimum condition for measurement of the pressure broadening coefficient. The Superconducting Submillimeter-wave Limb Emission Sounder (SMILES) was designed to monitor the volume mixing ratio of trace gases including HO2 in the Earth's upper atmosphere using these transitions. The precise measurement of pressure broadening coefficient γ in terms of the half width at half maximum is required in order to retrieve the atmospheric volume mixing ratio. In this work, γ coefficients of the 625.66 GHz transition were determined for N2 and O2 at room temperature as γ(N2)=4.085±0.049 MHz/Torr and γ(O2)=2.578±0.047 MHz/Torr with 3σ uncertainty. Similarly, the coefficients of the 649.70 GHz transition were determined as γ(N2)=3.489±0.094 MHz/Torr and γ(O2)=2.615±0.099 MHz/Torr. The air broadening coefficients for the 625.66 GHz and 649.70 GHz lines were estimated at γ(air)=3.769±0.067 MHz and 3.298±0.099 MHz respectively, where the uncertainty includes possible systematic errors. The newly determined coefficients are compared with previous results and we discuss the advantage of the mercury-photosensitized reaction for HO2 generation. In comparison with those of other singlet molecules, the pressure broadening coefficients of the HO2 radical are not much affected by the existence of an unpaired electron. 相似文献
13.
《Journal of Electron Spectroscopy and Related Phenomena》2005,142(3):241-252
In this paper angularly resolved photoelectron spectra (PES) and constant-ionic-state (CIS) spectra are presented for the atmospherically important species N and OH.The natural width Γ, line shape parameters q and ρ2 and discrete oscillator strengths f have been measured for the members of the N*[2s2p3(5S), np] (4P) ← N(4S) autoionizing resonances for n = 5–10. The n = 5 parameters calculated in this work are in good agreement with the values obtained previously whereas for the resonances with n = 6–10 the values of these parameters are reported for the first time. The asymmetry parameter (β) for the first band of N atoms, the N+(3P) ← N(4S) ionization, has also been measured in the photon energy range of the above autoionizing resonances.For OH, CIS spectra have been recorded for the first photoelectron band corresponding to the ionization OH+(X3Σ−, v+ = 0) ← OH(X2Π, v″ = 0). In these spectra, rotationally partially resolved bands associated with OH*(a1Δ3d, v′ = 0) ← OH(X2Π, v″ = 0) resonances have been observed. Suggestions for their assignment are made on the basis of their positions and band simulations which use rotational line strength calculations. 相似文献
14.
Zekai Hong King-Yiu Lam Ritobrata Sur Shengkai Wang David F. Davidson Ronald K. Hanson 《Proceedings of the Combustion Institute》2013,34(1):565-571
Hydrogen peroxide (H2O2) and hydroperoxy (HO2) reactions present in the H2O2 thermal decomposition system are important in combustion kinetics. H2O2 thermal decomposition has been studied behind reflected shock waves using H2O and OH diagnostics in previous studies (Hong et al. (2009) [9] and Hong et al. (2010) [6,8]) to determine the rate constants of two major reactions: H2O2 + M → 2OH + M (k1) and OH + H2O2 → H2O + HO2 (k2). With the addition of a third diagnostic for HO2 at 227 nm, the H2O2 thermal decomposition system can be comprehensively characterized for the first time. Specifically, the rate constants of two remaining major reactions in the system, OH + HO2 → H2O + O2 (k3) and HO2 + HO2 → H2O2 + O2 (k4) can be determined with high-fidelity.No strong temperature dependency was found between 1072 and 1283 K for the rate constant of OH + HO2 → H2O + O2, which can be expressed by the combination of two Arrhenius forms: k3 = 7.0 × 1012 exp(550/T) + 4.5 × 1014 exp(?5500/T) [cm3 mol?1 s?1]. The rate constants of reaction HO2 + HO2 → H2O2 + O2 determined agree very well with those reported by Kappel et al. (2002) [5]; the recommendation therefore remains unchanged: k4 = 1.0 × 1014 exp(?5556/T) + 1.9 × 1011+exp(709/T) [cm3 mol?1 s?1]. All the tests were performed near 1.7 atm. 相似文献
15.
《Solid State Ionics》2006,177(13-14):1149-1155
The Lu2+xTi2−xO7−x/2 (x = 0; 0.052; 0.096; 0.286; 0.44; 0.63; 33.3–49 mol% Lu2O3) nanoceramics with partly disordered pyrochlore-type structure are prepared by sintering freeze-dried powders obtained by a co-precipitation technique with 1600 °C annealing. Similar to pyrochlore-like compositions in the zirconate system, some of the new titanates are good oxide-ion conductors in air. The new solid-state electrolytes have oxide-ion conductivity in the interval of 1.0 × 10− 3 – 2.5 × 10− 3 S/cm at 740 °C in air. This value of conductivity is comparable with that of ZrO2/Y2O3 ceramics. The conductivity of Lu2+xTi2−xO7−x/2 depends on the chemical composition. The highest ionic conductivity is exhibited by nearly stoichiometric Lu2+xTi2−xO7−x/2 (x = 0.096; 35.5 mol% Lu2O3) material containing ∼ 4.8 at.% LuTi anti-site defects. 相似文献
16.
《Photonics and Nanostructures》2014,12(5):515-526
Dye sensitized solar cells (DSSCs) were fabricated based on coumarin NKX-2700 dye sensitized bi-layer photoanode and quasi-solid state electrolyte sandwiched together with cobalt sulfide coated counter electrode. A novel bi-layer photoanode has been prepared using composite mixtures of 90 wt.% TiO2 nanoparticles + 10 wt.% TiO2 nanowires (TNPWs) as active layer and Nb2O5 is coated on the active layer, which acts as scattering layer. Hafnium oxide (HfO2) was applied over the TNPWs/Nb2O5 photoanode film, as a blocking layer. TiO2 nanoparticles (TNPs), TiO2 nanowires (TNWs) and TNPWs/Nb2O5 were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The sensitizing organic dye coumarin NKX-2700 displayed maximum absorption wavelength (λmax) at 525 nm, which could be observed from the UV–vis spectrum. DSSC-1 fabricated with composite bi-layer photoanode revealed enhanced photo-current efficiency (PCE) as compared to other DSSCs and illustrated photovoltaic parameters; short-circuit current JSC = 18 mA/cm2, open circuit voltage (VOC) = 700 mV, fill factor (FF) = 64% and PCE (η) = 8.06%. The electron transport and charge recombination behaviors of DSSCs were investigated by electrochemical impedance spectra (EIS) and the results illustrated that the DSSC-1 showed the lowest charge transport resistance (Rtr) and the longest electron lifetime (τeff). Therefore, in the present investigation, it could be concluded that the novel bi-layer photoanode with blocking layer increased the short circuit current, electron transport and suppressed the recombination of charge carriers at the photoanode/dye/electrolyte interface in DSSC-1. 相似文献
17.
《Solid State Ionics》2006,177(7-8):691-695
Single crystals of the lithium-rich lithium manganese oxide spinels Li1 + xMn2 − xO4 with x = 0.10 and 0.14 have been successfully synthesized in high-temperature molten chlorides at 1023 K. The single-crystal X-ray diffraction study confirmed the cubic Fd3¯m space group and the lattice parameters of a = 8.2401(9) Å for x = 0.10 and a = 8.2273(10) Å for x = 0.14 at 300 K, respectively. The crystal structures have been refined to the conventional values R = 3.7% for x = 0.10 and R = 3.1% for x = 0.14, respectively. Low-temperature single-crystal X-ray diffraction experiments revealed that these single crystal samples showed no phase transition between 100 and 300 K. The electron-density distribution images in these compounds by the single-crystal MEM analysis clearly showed strong covalent bonding features between the Mn and O atoms due to the Mn–3d and O–2p interaction. 相似文献
18.
《Solid State Ionics》2006,177(1-2):105-112
Five compositions of Li[Co1 −2x(Li1 / 3Mn2 / 3)x(Ni1 / 2Mn1 / 2)x]O2 solid solutions ( x = 0.1, 0.2, 0.3, 0.4, and 0.5) were synthesized using a sol–gel method with three end members of LiCoO2, Li2MnO3(Li[Li1 / 3Mn2 / 3]O2), and Li[Ni0.5Mn0.5]O2. The compositions of metals in transition metal sites were changed to see the effect of them on electrochemical behavior of the solid solutions. All the samples were nano-sized semi-spherical shaped particles with a layered structure. The reduction of cobalt content (the increase of other metals) in the sites increases the lattice parameters, a and c, resulting in the shift of Raman and XRD peak positions. The discharge capacity fading turned serious at higher Co contents, but it was significantly diminished with the decrease of Co content. At lower Co contents, the capacity increased with cycle numbers. The most stable voltage profile was obtained from the composition of Li[Li1 / 15Co3 / 5Ni1 / 10Mn7 / 30]O2 (x = 0.2). 相似文献
19.
《Solid State Ionics》2006,177(13-14):1205-1210
A comparative investigation of the much-studied La2NiO4+δ (n = 1) phase and the higher-order Ruddlesden-Popper phases, Lan+1NinO3n+1 (n = 2 and 3), has been undertaken to determine their suitability as cathodes for intermediate-temperature solid-oxide fuel cells. As n is increased, a structural phase transition is observed from tetragonal I4/mmm in the hyperstoichiometric La2NiO4.15 (n = 1) to orthorhombic Fmmm in the oxygen-deficient phases, La3Ni2O6.95 (n = 2) and La4Ni3O9.78 (n = 3). High temperature d.c. electrical conductivity measurements reveal a dramatic increase in overall values from n = 1, 2 to 3 with metallic behavior observed for La4Ni3O9.78. Impedance spectroscopy measurements on symmetrical cells with La0.9Sr0.10Ga0.80Mg0.20O3−δ (LSGM-9182) as the electrolyte show a systematic improvement in the electrode performance from La2NiO4.15 to La4Ni3O9.78 with ∼ 1 Ω cm2 observed at 1073 K for the latter. Long-term thermal stability tests show no impurity formation when La3Ni2O6.95 and La4Ni3O9.78 are heated at 1123 K for 2 weeks in air, in contrast to previously reported data for La2NiO4.15. The relative thermal expansion coefficients of La3Ni2O6.95 and La4Ni3O9.78 were found to be similar at ∼ 13.2 × 10− 6 K− 1 from 348 K to 1173 K in air compared to 13.8 × 10− 6 K− 1 for La2NiO4.15. Taken together, these observations suggest favourable use for the n = 2 and 3 phases as cathodes in intermediate-temperature solid-oxide fuel cells when compared to the much-studied La2NiO4+δ (n = 1) phase. 相似文献
20.
The series of Gd4 ? xMxAl2O9 ? x/2 (M = Ca, Sr) with x = 0, 0.01, 0.05, 0.10 and 0.25 was prepared by the citrate complexation method. Both Gd4 ? xCaxAl2O9 ? x/2 and Gd4 ? xSrxAl2O9 ? x/2 show the monoclinic cuspidine structure with space group of P21/c up to 0.05–0.1 and 0.01–0.05 mol for Ca and Sr, respectively. Beyond the substitution limit of Gd4Al2O9, GdAlO3 and SrGd2Al2O7 appear as additional phases. The highest electrical conductivity obtained at 900 °C yielded σ = 1.49 × 10? 4 S/cm for Gd3.95Ca0.05Al2O8.98. In comparison, the conductivity of pure Gd4Al2O9 was σ = 1.73 × 10? 5 S/cm. The conductivities determined are in a similar range as those of other cuspidine materials investigated previously. The thermal expansion coefficient of Gd4Al2O9 at 1000 °C was 7.4 × 10? 6 K? 1. The phase transition between 1100 and 1200 °C reported earlier changes with increasing substitution of Ca and Sr. 相似文献