共查询到20条相似文献,搜索用时 13 毫秒
1.
E. A. Vovk T. G. Deineka A. G. Doroshenko V. F. Tkachenko A. V. Tolmachev R. P. Yakovetskii I. A. Petrusha V. N. Tkach V. Z. Turkevich N. I. Danilenko 《Journal of Superhard Materials》2009,31(4):252-259
The nanocrystalline Y3Al5O12 ceramics with different phase compositions, microstructures, and optical characteristics have been prepared by low-temperature
consolidation of the Y3Al5O12 powder at pressures from 6 to 7.7 GPa in the temperature range from 250 to 550°C. The conditions have been defined for obtaining
transparent nanostructured ceramics Y3Al5O12 having grains of size 20–40 nm and a transmission coefficient in the visible region of 40–45%. The criteria for the transparency
of the nanostructured ceramics have been formulated and the ways of an improvement of its optical characteristics are discussed. 相似文献
2.
A. A. Titov N. P. Sokolova M. V. Vorob’eva N. L. Opolchenova Z. V. Eremenko N. N. Stepareva 《Inorganic Materials》2009,45(8):884-888
Nanocrystalline ytterbia powders have been synthesized using different precursors prepared by precipitation from nitrate solutions: ytterbium carbonates, oxalates, and hydroxides. The powders have been characterized by X-ray diffraction and scanning electron microscopy. The nature of the precursor has no effect on the crystallization temperature of ytterbia but influences its microstructure. The particles range in shape from spherical to platelike. The average crystallite size of the Yb2O3 powders is 20–25 nm. Raising the heat-treatment temperature from 600 to 1000°C increases the crystallite size to 33–46 nm. The highest thermal stability is offered by the ytterbia powders prepared through carbonate decomposition. 相似文献
3.
S. A. Barannikova S. P. Buyakova L. B. Zuev S. N. Kul’kov 《Technical Physics Letters》2007,33(6):477-479
Spatiotemporal distributions of local components of the distortion tensor of a nonplastic material—yttria partially stabilized tetragonal zirconia (YTZ) ceramics—have been studied under active compressive straining conditions using double-exposure speckle photography techniques. The strain localization patterns are presented and the features of macroscopic strain inhomogeneity in the elastic state of YTZ ceramics are considered. 相似文献
4.
E. V. Dudnik V. V. Tsukrenko A. V. Shevchenko A. K. Ruban L. M. Lopato 《Inorganic Materials》2011,47(10):1107-1110
We have studied the properties of nanocrystalline ZrO2-Y2O3-CeO2-CoO-Al2O3 powders prepared via hydrothermal treatment of a mixture of coprecipitated hydroxides at 210°C. A number of general trends
are identified in the variation of the properties of the synthesized powders during heat treatment at temperatures from 500
to 1200°C. Our results demonstrate that the addition of 0.3 mol % CoO to nanocrystalline ZrO2-based powders containing 1 to 5 mol % Al2O3 allows one to obtain composites with good sinterability at a reduced temperature (1200°C). 相似文献
5.
D. A. Permin A. V. Novikova E. M. Gavrishchuk S. S. Balabanov A. A. Sorokin 《Inorganic Materials》2017,53(12):1330-1335
A technique has been developed for the self-propagating high-temperature synthesis of lutetium oxide (Lu2O3) powders using citric acid, glycine, and lutetium acetate as fuels. We have carried out thermodynamic analysis of synthesis conditions and examined the effect of the nature of the fuel on the properties of the resultant powders. Using vacuum sintering at a temperature of 1780°C and powders prepared with glycine as a fuel and containing 25 mol % yttrium oxide and 5 mol % lanthanum oxide as sintering aids, we have obtained transparent lutetium oxide-based ceramics. 相似文献
6.
E. V. Dudnik A. V. Shevchenko A. K. Ruban V. P. Red’ko L. M. Lopato 《Inorganic Materials》2010,46(2):172-176
We have studied the properties of nanocrystalline ZrO2〈3 mol % Y2O3〉 and 90 wt % ZrO2〈3 mol % Y2O3〉-10 wt % Al2O3 powders prepared via hydrothermal treatment of coprecipitated hydroxides at 210°C. The results demonstrate that Al2O3 doping raises the phase transition temperatures of the metastable low-temperature ZrO2 polymorphs and that the structural transformations of the ZrO2 and Al2O3 in the doped material inhibit each other. 相似文献
7.
Y2O3 + Nd2O3 co-stabilized ZrO2-based composites with 40 vol% WC were fully densified by pulsed electric current sintering (PECS) at 1350 °C and 1450 °C.
The influence of the PECS temperature and Nd2O3 co-stabilizer content on the densification, hardness, fracture toughness and bending strength of the composites was investigated.
The best combination of properties was obtained for a 1 mol% Y2O3 and 0.75 mol% Nd2O3 co-stabilized composite densified for 2 min at 1450 °C under a pressure of 62 MPa, resulting in a hardness of 15.5 ± 0.2
GPa, an excellent toughness of 9.6 ± 0.4 MPa.m0.5 and an impressive 3-point bending strength of 2.04 ± 0.08 GPa. The hydrothermal stability of the 1 mol% Y2O3 + 1 mol% Nd2O3 co-stabilized ZrO2-WC (60/40) composites was compared with that of the equivalent 2 mol% Y2O3 stabilized ceramic. The double stabilized composite did not degrade in 1.5 MPa steam at 200 °C after 4000 min, whereas the
yttria stabilized composite degraded after less than 2000 min. Moreover, the (1Y,1Nd) ZrO2-WC composites have a substantially higher toughness (~9 MPa.m0.5) than their 2Y stabilized equivalents (~7 MPa.m0.5). 相似文献
8.
L. G. Jacobsohn K. Serivalsatit C. A. Quarles J. Ballato 《Journal of Materials Science》2015,50(8):3183-3188
0.25 at.% Er-doped Sc2O3 transparent ceramics fabricated using the two-step sintering method with different combinations of sintering temperatures were investigated by positron annihilation spectroscopy. Analysis of the broadening of the annihilation photopeak revealed the presence of the same type of defect in all samples. The lack of long lifetimes (τ ≥ 2 ns) suggested no positronium formation or the lack of trapping sites large enough to trap positronium for long enough time for the annihilation to be observed. Analysis of positron annihilation lifetime revealed the presence of a single lifetime that ranged from 208 to 219 ps, depending on the sintering conditions. These results also suggest the absence of a significant presence of vacancy clusters and other larger open-volume defects, and that the dominant open-volume defect corresponds to monovacancies and/or complex defects associated with monovacancies. The bulk lifetime of Er-doped scandia is estimated to be equal or lower than 208 ps. 相似文献
9.
A series of glass comprising of SiO2–MgO–B2O3–Y2O3–Al2O3 in different mole ratio has been synthesized. The crystallization kinetics of these glasses was investigated using various
characterization techniques such as differential thermal analysis (DTA), thermo gravimetric analysis (TGA), X-ray diffraction
(XRD), and scanning electron microscopy (SEM). Crystallization behavior of these glasses was markedly influenced by the addition
of Y2O3 instead of Al2O3. Addition of Y2O3 increases the transition temperature, T
g, crystallization temperature, T
c and stability of the glasses. Also, it suppresses the formation of cordierite phase, which is very prominent and detrimental
in MgO-based glasses. The results are discussed on the basis of the structural and chemical role of Y3+ and Al3+ ions in the present glasses. 相似文献
10.
O. Ya. Manashirov A. N. Georgobiani V. B. Gutan E. M. Zvereva A. N. Lobanov 《Inorganic Materials》2012,48(7):721-726
We have established the key trends in the variation of the intensity of the visible and IR luminescence of (Y1 − x − y − z Yb x Tm y Er z )2O2S solid solutions in relation to their composition under laser excitation at λ = 0.940 μm. The results obtained have been used to develop multifunctional anti-Stokes white phosphors with various tinges and a predetermined relative intensities of visible and IR emission bands. 相似文献
11.
Venugopalan Anbarasu Appasamy Manigandan Thangavelu Karthik Kandasamy Sivakumar 《Journal of Materials Science: Materials in Electronics》2012,23(6):1201-1209
The synthesis and characterization of Y2−xFexO3 (where x = 0–0.3) compounds has been carried out for their importance in the field of multiferroic materials. The powder
X-ray diffraction reveal that the compounds Y1.95Fe0.05O3, Y1.9Fe0.1O3, Y1.85Fe0.15O3 and Y1.8Fe0.2O3 crystallize in tetragonal structure whereas Y1.75Fe0.25O3 and Y1.7Fe0.3O3 compounds crystallize in orthorhombic structure. The change in crystal system with respect to the concentration of Fe may
be attributed to the variation in occupancy position of Fe3+ into the Y3+ site of Y2O3 system. Variation in crystal structure, surface morphology and composition was studied by micro-Raman analysis, SEM and EDX
analysis. The shift in intense Raman signals from 426 to 385 cm−1 confirms the change in the crystal structure of the prepared compounds. Further it is also identified that the Eg mode of vibration is the dominant in the Fe substituted compounds. The substitution of Fe in the Y2O3 system leads to the increase in the intensity of resonance band, which indicates a large polarisability variation in the
Y2−xFexO3 compounds. Diffused reflectance studies show a red shift in energy gap values while increasing the concentration of Fe. The
room temperature magnetization and electron paramagnetic resonance studies reveal that the incorporation of Fe in the Y2O3 system leads to magnetic phase change from diamagnetic to ferromagnetic. The electric polarization studies imply that the
substitution of lower ionic radii element Fe3+ in the Y3+ site leads to distortion in the lattice and show the way to spontaneous dipole moment and it was found that the Y1.8Fe0.2O3 compound exhibits the possibility of multiferroic behaviour. Therefore this paper explores the possibility of inducing ferromagnetic
and ferroelectric behaviour in the Fe substituted yttrium oxide system. 相似文献
12.
Mohamed M. Gomaa Hussein Darwish Saad M. Salman 《Journal of Materials Science: Materials in Electronics》2008,19(1):5-15
The ac electrical properties of some lithium silicate glasses and glass-ceramics containing varying proportions of Y2O3 and/or Fe2O3 were measured to investigate their electronic hopping mechanism. There is a clear variation of these properties with composition.
The obtained results were related to the concentration and role of Y2O3 and/or Fe2O3 in the lithium silicate glass structure. In crystalline solids the electrical properties data obtained were correlated to
the type and content of the mineral phases formed as indicated by X-ray diffraction analysis (XRD).
The conductivity, dielectric constant and dielectric loss of the studied glasses were studied using the frequency response
in the interval 30 Hz–100 KHz and the effect of compositional changes on the measured properties was investigated. The measurements
revealed that the electrical responses of the samples were different and complex. The addition of Y2O3 generally, decreased the ac conductivity, dielectric constant and dielectric losses of the lithium silicate glasses. The
addition of Fe2O3 in Y2O3-containing glasses increases the conductivity, while, the dielectric constant and dielectric losses were found to be decreased.
However, the addition of Fe2O3 instead of Y2O3 led to decrease the ac conductivity and increased their dielectric constant and dielectric losses.
The obtained data were argued to the internal structure of the lithium silicate glass and the nature or role-played by weakness
or rigidity of the structure of the sample.
Lithium disilicate-Li2Si2O5, lithium metasilicate-Li2SiO3, two forms of yttrium silicate Y2Si2O7 & Y2SiO5, iron yttrium oxide-YFeO3, lithium iron silicate-LiFeSi2O6 and α-quartz phases were mostly developed in the crystallized glasses.
The conductivity of the crystalline materials was found to be relatively lower than those of the glass. At low frequency,
as the Y2O3 content increased the ac conductivity, dielectric constant and dielectric loss data of the glass-ceramics decreased. However,
the addition of Fe2O3 to the Y2O3 containing glass-ceramic led to increase the conductivity. The addition of high content of Fe2O3 instead of Y2O3 in the glass ceramic led to increase the ac conductivity. 相似文献
13.
The photoluminescence and short-time persistence (afterglow) kinetics in pure and doped Y2O3-Al2O3 crystals excited with UV laser pulses (12 ns, 337 nm) were studied using samples irradiated with gamma quanta from a 60Co source to a dose from 104 to 107 Gy. The relaxation time of the samples studied increases, with decreasing symmetry of the crystal lattice, in the following
order: garnet—orthoaluminate—ruby—yttria. The afterglow duration and intensity significantly decrease in gamma-irradiated
crystals, which is explained by the predominant recombination of close electron-hole pairs. Garnet-neodymium crystals are
characterized by high radiation stability and fast relaxation kinetics. 相似文献
14.
M. A. Borik M. A. Vishnyakova V. P. Voitsitskii A. V. Kulebyakin E. E. Lomonova V. A. Myzina V. V. Osiko V. A. Panov 《Inorganic Materials》2007,43(11):1223-1229
We have studied the effect of composition and growth conditions on the structure and properties of 2.5–5 mol % Y2O3 partially stabilized ZrO2 crystals grown by directional solidification in a cold-wall crucible. The phase composition and density of the crystals have been determined. The crystals are shown to be uniform in composition, with local changes in Y2O3 content within ±0.5 mol %. The dimensions and quality of the single crystals are influenced by the growth conditions. 相似文献
15.
Şeyda Duman Bakiye Çakır Alev Aydıner 《Journal of Superconductivity and Novel Magnetism》2016,29(9):2275-2280
In this work, a cylindrical YBa2Cu3O7?x (Y123) sample having 20 mm diameter and 8 mm height was prepared by the cold-seeding method using an Nd123 seed, and the crystal growth process was performed in an alumina crucible with a Y2O3 layer. The structural orientation of the specimens was measured by an X-ray diffractometer (XRD). As a result of the X-ray diffraction data, only (00 l) peaks were observed, indicating that all specimens are highly oriented with the c-axis perpendicular to the top surface. Resistivity measurements of a 1.5-mm-thick rectangular sample were performed by a standard four-probe method at temperatures between 60 and 100 K at a rate of 4 K/min using a Physical Properties Measurement System (PPMS) under various constant magnetic fields from 1 to 5 T with the magnetic field parallel to the c-axis, which is the direction of pressing into the zero-field cooling regime (ZFC). Fluctuation-induced conductivity analysis was performed to investigate the availability of the sample for technology. The analysis showed that the critical exponents were in agreement with theoretical values; thus, it was seen that superconducting properties of the sample were good and the 3D fluctuation was dominant. Because of the large c?axis coherence length (ξ c(0)) and small anisotropy, the superconducting properties became better. Furthermore, the fluctuations were reduced, and it was understood that the effective availability of the sample in technology will be possible. 相似文献
16.
A. V. Strel’tsov V. P. Dmitrienko T. A. Akmaeva S. V. Kudryavtsev A. O. Dmitrienko K. A. Razumov 《Inorganic Materials》2009,45(8):889-893
The influence of activation of the Y2O3 matrix of the Y2O3:Eu3+ phosphor by Bi3+ ions on the luminescence of Eu3+ and Bi3+ ions in it and on conditions of the excitation energy transfer to luminescence centers is studied. It is shown that the presence of Bi3+ ions leads to the appearance of recombination luminescence with participation of bismuth ions at low concentrations (up to 6–8 at %) of the dominant activator europium and to an increase in the threshold of intrinsic concentration quenching of its luminescence. 相似文献
17.
S. Mirzamohammadi M. Kh. Aliov A. R. Sabur A. Hassanzadeh-Tabrizi 《Materials Science》2010,46(1):76-86
We study the electrodeposition of tertiary Alumina/Yitria/carbon nanotube (Al2O3/Y2O3/CNT) nanocomposite by using pulsed currents. The process of coating is performed in a nickel-sulfate bath and the nanostructure
of the obtained compound layer is examined with the help of high-precision figure analysis of SEM nanographs. The effects
of process variables, i.e., the Y2O3 concentration, treatment time, current density, and the temperature of electrolyte are experimentally investigated. Statistical
methods are used to achieve the minimum wear rate and average size of nanoparticles. Finally, the percentage contributions
of different effective factors are revealed, and the confirmation run showed the validity of the obtained results. It is also
revealed that the wear properties of the coatings undergo significant changes if the sizes of nanoparticles change. The atomic-force
microscopy (AFM) and transmissionelectron microscopy (TEM) analyses confirm the smooth surfaces and average sizes of nanoparticles
in the optimal coating. 相似文献
18.
E. F. Dolzhenkova V. A. Belous A. G. Doroshenko I. A. Petrusha V. F. Tkachenko G. N. Tolmacheva V. Z. Turkevich R. P. Yavetskii 《Inorganic Materials》2011,47(10):1160-1167
Using micro- and nanoindentation techniques, we have studied the mechanical properties of Y3Al5O12 optical ceramics: coarse-grained, prepared by vacuum sintering, and nanostructured, prepared by high-pressure, low-temperature
sintering. The effect of grain size on the strength of the ceramics has been analyzed. 相似文献
19.
A. P. Kazin M. N. Rumyantseva V. E. Prusakov I. P. Suzdalev Yu. V. Maksimov V. K. Imshennik S. V. Novochikhin A. M. Gaskov 《Inorganic Materials》2010,46(11):1254-1259
Nanocrystalline nickel ferrite with a crystallite size from 3 to 40 nm has been prepared by spray pyrolysis. The 57Fe Mössbauer spectrum of NiFe2O4 samples has been found to vary systematically with crystallite size. The sensing response of the nanocrystalline nickel ferrite to 50 ppm NH3 has been studied using in situ conductance measurements. NiFe2O4 offers a strong sensing response to ammonia at the level of its maximum concentration limit. The optimum nickel ferrite crystallite size and temperature for ammonia detection are determined. 相似文献
20.
V. V. Ivanov S. N. Ivanov A. S. Kaigorodov A. V. Taranov E. N. Khazanov V. R. Khrustov 《Inorganic Materials》2007,43(12):1365-1370
Transparent Nd-doped cubic Y2O3 ceramics have been prepared by magnetic pulse compaction of nanopowders, followed by sintering. Analysis of the transport of nonequilibrium thermal phonons at liquid helium temperatures has been used to assess the effect of preparation conditions on the microstructure, average thickness, and stability of the grain boundaries in the ceramics. The average grain-boundary thickness in the transparent ceramics is shown to be comparable to the lattice parameter of Y2O3. 相似文献