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Rare earth and barium titanates are useful as ferroelectric, dielectric, and optical materials. Measurements of their thermophysical properties in the liquid state can help guide melt processing technologies for their manufacture and advance understanding of fragile liquids' behavior and glass formation. Here, we report the density, thermal expansion, viscosity, and surface tension of molten BaTi2O5, BaTi4O9, and 83TiO2-17RE2O3 (RE = La or Nd). Measurements were made using electrostatic levitation and droplet oscillation techniques in microgravity, which provide access to quiescent liquid droplets and deep supercooling of 510–815 K below the equilibrium melting points. Densities were measured over 900–2400 K. Viscosities were similar for all four compositions, increasing from ∼10 mPa s near 2100 K to ∼30 mPa s near 1750 K. Surface tensions were 450–490 dyn cm−1 for the rare earth titanates and 383–395 dyn cm−1 for the barium titanates; surface tensions of all compositions had small or negligible temperature dependence over 1700–2200 K. For solids recovered after melt quenching, x-ray microtomography revealed the fracture mechanics in crystalline products and minimal internal porosity in glass products, likely arising from entrapped gas bubbles. Internal microstructures were generally similar for products processed either in microgravity or in a terrestrial aerodynamic levitator. [ABSTRACT FROM AUTHOR]

The densities of molten Y2O3‐Al2O3 compounds, including yttrium aluminum garnet (Y3Al5O12), were determined over a wide temperature range that included an undercooled region, using an electrostatic levitation furnace. The density of the molten Y3Al5O12 varied with temperature according to the relationship 3750 − 0.25(T − Tm) (kg/m3) with Tm = 2240 K and for the range of 1300 K ≤ T ≤ Tm, yielding the thermal expansion coefficient ɑ = 6.7×10−5 K−1. The molar volumes of molten (100‐x)Y2O3‐xAl2O3 (x = 0, 33.3, 50, 55, 62.5, 76.5, 81.5, or 100 mol%) were found to vary with the value of x in a linear manner within the superheated temperature range. However, the molar volumes in the undercooled region deviated from those calculated using an ideal solution model owing to attractive interactions between Y2O3 and Al2O3. [ABSTRACT FROM AUTHOR]

We measured the thermophysical properties of molten gallium oxide (Ga2O3) in a contamination-free and microgravity environment by using the electrostatic levitation furnace in the International Space Station. The density of molten Ga2O3 was obtained over a wide temperature range of 2001â€"2174 K including the undercooled state and found to be expressed as 5004.8â€"0.4478(T âˆ' T m) (kg mâˆ'3), where T m, the melting point, is 2066 K. Measurements of its viscosity and surface tension were also performed by using the drop oscillation method and these values were found to be 337.0 (10âˆ'3 N mâˆ'1) and 13.6 (10âˆ'3 Pa·s) at 2228 K, respectively. [ABSTRACT FROM AUTHOR]

Liquid densities of three lanthanoid sesquioxides (Tm2O3, Yb2O3, and Lu2O3), whose melting temperatures are above 2400 °C, were measured using an electrostatic levitation furnace onboard the International Space Station (ISS). Each sample was positively charged, and its position was controlled by Coulomb forces between the sample and the surrounding electrodes. Following heating and melting of the sample by high-power lasers, its volume was calculated from its spherical shape in its liquidus phase. After weighing the mass of the sample returned to Earth, its density was determined. The densities (ρ) of Tm2O3, Yb2O3, and Lu2O3 can be expressed as ρTm2O3 = 8304 − 0.18 × (T − Tm), ρYb2O3 = 8425 − 0.55 × (T − Tm), and ρLu2O3 = 8627 − 0.43 × (T − Tm), respectively, where Tm is their melting temperatures. [ABSTRACT FROM AUTHOR]

The defect structures of impurity-doped congruent lithium niobates (c-LN) were determined for impurities with various valences, including divalent, trivalent, and tetravalent impurities, in a concentration range where antisite niobium (NbLi) exists. On the basis of the "Li site vacancy model," six kinds of defect structures in impurity-doped c-LN are possible. Using thermodynamic constraints, these can be narrowed down to two kinds. The first structure is that in which impurities, vacancies and Nb exist as defects in the Li site and no defects exist in the Nb site (structure A), described as {[LiLi]?1-5x-jy[NbLi]x[MLi]y[VLi]4x+(j-1)y}[NbNb][OO]3 (V: vacancy, M: impurity, j: valence of impurity, x, y: compositional variable (≠0), Li/Nb?=?congruent ratio). {[Li×Li]1-5x-2y[Nb∙∙∙∙Li]x[M∙Li]y[V'Li]4x+y}[Nb×Nb][O×O]3 is an example by the Kröger-Vink notation for divalent M. In the second structure, vacancies and Nb exist as defects in the Li site and impurities exist as defects in the Nb site (structure B), described as {[LiLi]1-5x-(j-5)y[NbLi]x[VLi]4x+(j-5)y}{[NbNb]1-y[MNb]y}[OO]3. {[Li×Li]1-5x+y[Nb∙∙∙∙Li]x[V'Li]4x-y}{[Nb×Nb]1-y[M'Nb]y}[O×O]3 is an example for tetravalent M. Since the relationship between impurity concentration and lattice constants for structures A and B differs, the defect structures can be differentiated by analyzing lattice constant variations as a function of impurity concentration. The results show that the defect structure of divalent and trivalent impurity-doped c-LN is structure A and that of tetravalent impurity-doped c-LN is structure B. The NbLi concentration increased with increasing tetravalent impurity concentration. In contrast, the NbLi concentration decreased with increasing divalent and trivalent impurities, leading to suppression of optical damage. The valence of an impurity determines whether the impurity is located in the Li site or Nb site in c-LN, consequently determining whether NbLi decreases or increases when the population of the impurity changes. [ABSTRACT FROM AUTHOR]

The effect of point defects on the Curie temperature ( Tc) of LiNbO3 ( LN) was investigated by combining Tc measurements with an analysis of the defect structures of LN doped with impurities having various valences. The data show that Tc of congruent LN increases with the impurity concentration up to around 3 and 2 mol% for divalent and trivalent impurities, respectively, whereas it decreases continuously with increased concentrations of tetravalent impurities. These Tc variations were examined with respect to the defect structures of impurity-doped LN, which are expressed in the form chemical formulae using Kröger-Vink notation. The defect structures of divalent and trivalent impurity-doped LN are [ABSTRACT FROM AUTHOR]