Addition Of Ta2O5 Research Articles

Density and Surface Tension of the System KF–K2TaF7–Ta2O5

The density of the system KF–K2TaF7–Ta2O5 was measured by the Archimedean method and the surface tension by the maximum bubble pressure method in the composition range up to 20 mol% Ta2O5. The density in the system KF–K2TaF7–Ta2O5 increases from KF through K2TaF7 to Ta2O5 and the surface tension increases from K2TaF7 through KF to Ta2O5. Based on the measured density values, the molar volumes of the binary and ternary melts at 860 °C, 900 °C and 950 °C were calculated as well as the partial molar volumes of particular components in different binaries. The small negative deviation from ideal behaviour in the binary system KF–K2TaF7 was identified by the calculation of the molar excess volume. The formation of complex anions [TaF8]3− is expected in this binary system. The surface tension decreases monotonically from KF to K2TaF7 in the binary system KF–K2TaF7. In the next two binaries KF–Ta2O5 and K2TaF7–Ta2O5 decrease of the surface tension was observed with the initial addition of Ta2O5 followed by the increase of the surface tension by further addition of Ta2O5. Based on measured data it was concluded that in binaries KF–Ta2O5 and K2TaF7–Ta2O5 the surface active component is Ta2O5 and in the binary KF–K2TaF7 the surface active component is K2TaF7. Mathematical description of the concentration dependence of the molar volume and surface tension of the measured ternary system was done by the polynomial function at 860°C, 900°C, and at 950°C.

Effect of Ta2O5 addition on the superconducting properties of REBa2Cu3Oy

We have investigated the effect of Ta2O5 addition on the superconducting properties of REBa2Cu3Oy (RE=Er, Sm and Eu: REBCO) prepared by a powder-sintering method. Tc(zero) values showed no degradation up to 1.0wt.% Ta2O5 addition for ErBCO samples. EuBCO and SmBCO samples showed the increase in Tc(zero) from 89K to 94K by the addition of 1wt.% Ta2O5, and 80K to 94K by the addition of 2wt.% Ta2O5, respectively. Jc values at B=0.5T increased by two times the pure samples for ErBCO with 1.0wt.% addition, four times for EuBCO with 1.5wt.% addition, and 33 times for SmBCO with 1.0wt.% addition. The formation of REBa2TaO6 was observed for the Ta2O5-added REBCO samples.

Effect of Ta2O5 on Microstructure and Microwave Dielectric Properties of Ba(Zn1/3Ta2/3)O3 Ceramics

When Ta2O5 was added to Ba(Zn1/3Ta2/3)O3 (BZT) ceramics, the degree of the 1:2 ordering increased and the Ba3Ta5O15 second phase was formed. Grain growth and liquid phase were also found in Ta2O5 added BZT ceramics sintered above 1580°C. The liquid phase, which is responsible for grain growth, is related to the Ba3Ta5O15 second phase. The Q-value of BZT ceramics sintered above 1580°C was considerably increased with the addition of a small amount of Ta2O5. Since the relative density decreased with the addition of Ta2O5, the increase of the Q-value is not related to the relative density. In contrast, the improvement of the Q-value could be explained by the increase in the grain size because the average grain size increased with the addition of Ta2O5. When a large amount of Ta2O5 was added, however, the Q-value became very low even though the grain size was very large. The low Q-value might be attributed to the low relative density and the presence of a large amount of the Ba3Ta5O15 second phase.

Effect of Ta2O5 Addition on Microstructure of Mo5Si3 Particle Reinforced Si3N4 Composite with Grain Boundary Phase of Yb2Si2O7

Mo5Si3 particle reinforced Si3N4 composite with crystallized grain boundary phase of Yb2Si2O7 was synthesized in-situ by sintering a green compact that contained Si3N4, MoO3, Ta2O5, and Yb2O3 powders. The reaction between Si3N4, MoO2, Ta2O5, and Yb2O3 at high temperature generated the Mo5Si3 particles, the complex molybdenum and tantalum silicide particles, and the grain boundary phase of Yb2Si2O7 simultaneously. In the Mo5Si3-Yb2Si2O7-Si3N4 composite, most of Mo5Si3 particles residing at the grain boundary phase, and had an average size of 0.18 μm. The addition of Ta2O5 promoted the formation of Mo5Si3 particle in Si3N4 grain and the generation of the Yb2Si2O7 nano-particle in the grain boundary phase. The grain boundary phase and the Si3N4 grains were reinforced by the sub-micrometer sized Mo5Si3 particles and Yb2Si2O7 nano-particles, which improved the strength of Si3N4. The crystallization of grain boundary phase was almost completed by adding the MoO3, Ta2O5, and Yb2O3, while a small amount of amorphous phase and the thin amorphous films were detected from the grain boundary pockets, and the interfaces between the Si3N4, Yb2Si2O7, and Mo5Si3, respectively.

Effect of Ta2O5 on Dielectric Properties of Forsterite Ceramics

ABSTRACTFor the millimeter-wave dielectrics, forsterite-based ceramics were produced. Stoichiometric forsterite ceramics (Mg2SiO4) shows porous microstructure and very low Q*f values, which is not suitable for dielectrics in the microwave and millimeter-wave bands. The small addition (0.025 mol%) of Ta2O5 instead of SiO2 enhanced the sinterability of forsterite ceramics. The sintering temperature was reduced more than 150°C by the addition of Ta2O5. The density was greatly increased by Ta2O5 addition. The dielectric constant and Q*f of 0.025 mol% Ta2O5 modified forsterite sintered at 1500°C was 7.3 and 150, 000, respectively in microwave band (8–11GHz). The dielectric constant and Q*f of the same sample measured at 55GHz was 6.7 and 179, 000, respectively. Further addition of Ta2O5 decreases the sintering temperature.

Dielectric and Magnetic Properties of Ta2O5-doped PrFeO3–PbTiO3 and PrFeO3–BiFeO3 Ceramics

Polarization-electric field (P–E) and magnetization-magnetic field (M–H) hysteresis curves have been characterized in the solid solutions of (1-x)PrFeO3–xPbTiO3+yTa2O5 (y=0–0.015 mole) and 0.2PrFeO3–0.8BiFeO3. Neutron and X-ray diffraction data were collected for crystal structural analysis. The (1-x)PrFeO3–xPbTiO3 were ferromagnetic at 0.2<x<0.7. Remanent magnetization Mr decreased from 0.09 emu/g at x=0.4 to 0.02 emu/g at x=0.65. The P–E curve measurements showed that the solid solution was paraelectric at x=0.4. The shape of the P–E curve showed a more ferroelectric nature at x=0.65. Remanent polarization Pr was 0.8 µC/cm2 at x=0.65. The Rietveld refinement of neutron data showed a structural transition occuring at x≥0.7 from Pbnm (a=5.552, b=5.540 Å, c=7.833 Å) to I4cm (a=b=5.54 Å, c=7.841 Å) The structural analysis indicates that the solid solutions are ferroelectric only at x>0.6. The 0.2PrFeO3–0.8BiFeO3 showed a spontaneous magnetization of 0.3 emu/g at room temperature and remanent polarization Pr of 0.6 µC/cm2. Addition of Ta2O5 substantially changed the magnetic properties. The antiferromagnetic ordering is considered not to have a direct relationship with the weak ferromagnetism observed in this system.

Electric and Magnetic Properties of Ta-Doped Polycrystalline Mn-Zn Ferrite

The effect of Ta2O5 additive on the electric and magnetic properties of MnZn ferrites with fine grain size was studied A adding small amounts of Ta2O5 to the MnZn ferrite increased electric resistivity, while an excessive addition of Ta2O5 caused decrease in resistivity without significant grain growth. In a small amount of Ta2O5 the change in the electric resistivity can be explained by Ta 5+ substitution for Fe 3+ entailing disappearance of the oxygen defects. The excessive addition of Ta2O5 created the oxygen defects and the electrons which are promoted by the metallic ion defects and the thermal dissociation of oxygen.

Electrical resistance as a tool in determining the failure of fibres in a nicalon-reinforced LAS glass-ceramic with Ta2O5 additions

The electrical resistance of a Nicalon-reinforced lithium aluminosilicate glass-ceramic with Ta2O5 additions was used as an indicator of fibre and TaC/Carbon coating fracture during flexural testing. The resistivities of fibres in the composite were significantly lower than the free fibres owing to the high conductivity carbon and TaC coatings which formed during hot pressing. Hot-pressing times beyond 0.5 h resulted in a degradation of flexural strength via the formation of a strongly bonded TaC layer at the expense of the carbon debond layer.

Thin-film head materials for quasi-contact head/disk interface

The mechanical, physical, and tribological properties of ZrO2-Y2O3-Ta2O5 have been investigated in this article. Under noncontact conditions, the frictional coefficient of the composite was found to be less than 50% of the Al2O3-TiC material. And, under contact conditions, the damage against the media was less than 0.2 dB, comparable to the ferrite material. The slicing resistance of this material rapidly changed from 1 to 3 mol % Ta2O5 because of its fracture mode. It was found that addition of Ta2O5 stabilizes the tetragonal phase which was found to be unchanged by aging at 200 °C.

マイクロ波誘電体ＢａＴｉ４Ｏ９の誘電特性に及ぼす各種酸化物添加の影響

As a microwave dielectric. BaTi4O9 is profitable for its high Q value, however, it is disadvantageous for its high temperature coefficient.In our investigation reported here, we used ZnO-Ta2O5 system compounds said to own negative temperature coefficient, added them to BaTi4O9 and studied the effects.Results obtained are summarized as follows:(1) The addition of ZnO and Ta2O5 to BaTi4O9 improved both the Q value and temperature coefficient, and the best composition obtained were regarded thus; BaO:17.50mol%, TiO2:70.00mol%. Ta2O5:0.75mo1% and ZnO:11.75mol%.(2) We observed black part with poor Zn and white part with rich Zn in the structure both in the center and on the surface of sintered specimen above mentioned, and it was confirmed that the structure in the center was more coarsened than that on the surface, comparatively.(3) Adding Mn2O3 to BaTi4O9. we obtained identical structure in the center and on the surface, with the Q value and temperature coefficient both improved. It is confirmed that the most suitable amount of Mn2O3 to add is 0.18mol%, in this occasion.

Effect of Ta2O5 additions on phase formation during synthesis and sintering of ?-alumina based ceramics

We demonstrated the effect of the Ta2O5 additive on the process of phase formation during the synthesis of the powders and during sintering of β-alumina ceramics (as compared to stoichiometric sodium polyaluminate Na2O·5Al2O3). The presence of the additive increases the quantity of β″-Al2O3 phase and stabilizes it during low-temperature isothermal synthesis; during high-temperature sintering, it hinders the formation of the nonconducting α-Al2O3 phase; this is one of the main conditions required for obtaining β-alumina ceramics having a high ionic conductivity.

ChemInform Abstract: Low‐Thermal‐Expansion Polycrystalline Zirconyl Phosphate Ceramic: Solid‐Solution and Microcracking‐Related Properties.

AbstractThe effects of addition of Ta2O5 or Nb2O5 on the sintering and refractory properties of 2 ZrO2·P2O5‐based ceramics have been investigated.