Average Linear Thermal Expansion Coefficient Research Articles

Broadened negative thermal expansion operation-temperature window in antiperovskite Mn3Zn0.6Ge0.4N prepared by spark plasma sintering

Anti-perovskite manganese nitrides Mn3Zn0.6Ge0.4N with different crystallite size were prepared by spark plasma sintering (SPS) at different sintering temperatures. Their negative thermal expansion (NTE) properties were investigated. It was found that the width of NTE operation-temperature window (ΔT) broadens with decreasing crystallite size. Typically, a broad ΔT of 105K was obtained in the compound Mn3Zn0.6Ge0.4N with average crystallite size of 54nm sintered at 700°C, of which the average linear thermal expansion coefficient was estimated to be −13.5×10−6K−1 in the NTE operation-temperature window. This antiperovskite manganese nitride Mn3Zn0.6Ge0.4N with broadened ΔT around room temperature is more useful for practical applications.

Synthesis and tunable thermal expansion properties of Sc2−xYxW3O12 solid solutions

A new series of rare earth solid solutions Sc2−xYxW3O12 was successfully synthesized by the conventional solid-state method. Effects of doping ion yttrium on the crystal structure, morphology and thermal expansion property of as-prepared Sc2−xYxW3O12 ceramics were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TG), field emission scanning electron microscope (FE-SEM) and thermal mechanical analyzer (TMA). Results indicate that the obtained Sc2−xYxW3O12 samples with Y doping of 0≤x≤0.5 are in the form of orthorhombic Sc2W3O12-structure and show negative thermal expansion (NTE) from room temperature to 600°C; while as-synthesized materials with Y doping of 1.5≤x≤2 take hygroscopic Y2W3O12·nH2O-structure at room temperature and exhibit NTE only after losing water molecules. It is suggested that the obvious difference in crystal structure leads to different thermal expansion behaviors in Sc2−xYxW3O12. Thus it is proposed that thermal expansion properties of Sc2−xYxW3O12 can be adjusted by the employment of Y dopant; the obtained Sc1.5Y0.5W3O12 ceramic shows almost zero thermal expansion and its average linear thermal expansion coefficient is −0.00683×10−6°C−1 in the 25–250°C range.

Bulk growth and physical properties of diguanidinium phosphate monohydrate (G2HP) as a multi-functional crystal

Bulk single crystals of diguanidinium phosphate monohydrate (G2HP) with dimensions up to 55 × 28 × 27 mm3 have been grown by solution growth methods. Thermal properties including specific heat, thermal conductivity and thermal expansion were investigated as a function of temperature. The specific heat was measured to be 1.339 to 1.614 J g−1 K−1 over the temperature range of 293 to 347 K. The thermal conductivities are descending as the temperature increases. The average linear thermal expansion coefficients along a and c axes from 298 to 338 K are α11 = 1.878 × 10−5 K−1 and α33 = 1.930 × 10−5 K−1, respectively. The laser-induced damage threshold measurements show that the G2HP crystal possesses an excellent resistance to laser radiation with a high threshold up to 5.29 GW cm−2. The optical behaviors, including the transmission spectrum and reflective indexes, were investigated to study its linear and nonlinear optical properties. The results reveal that the crystal is a phase matchable nonlinear optical material in the visible and UV regions. A complete set of dielectric, elastic and piezoelectric constants of G2HP have also been measured, and the results display that the crystal also possesses fine piezoelectric properties with d14 = 10.00. Furthermore, the structure–property relationships are discussed on the basis of the crystal structure combined with theoretical calculations. As a multi-functional crystal, G2HP is a particularly promising candidate for a variety of potential applications in many fields.

Growth, morphology and anisotropic thermal properties of Nd-doped Sr3Y2(BO3)4 crystal

A high-quality Nd3+:Sr3Y2(BO3)4 laser crystal has been grown by the Czochralski method. The phase purity and accurate unit cell parameters were determined using X-ray powder diffraction; the unit cell parameters are calculated to be a=7.3933 (1)Å, b=15.9461 (2)Å, c=8.6967 (1)Å, and V=1025.29 (5)Å3. Effective segregation coefficients were measured and the optical homogeneity was further characterized by interferometry. A series of possible growth faces (hkl) were also deduced and compared with the as-grown crystal boules using the Bravais–Friedel–Donnay–Harker (BFDH) theory. A full set of thermal properties, including the thermal expansion, thermal diffusivity, specific heat, and thermal conductivity, were measured as a function of temperature. The average linear thermal expansion coefficients along different crystallographic directions were measured to be α11=7.04×10−6K−1, α22=15.32×10−6K−1 and α33=14.35×10−6K−1 over the temperature range 303.15–770.15K. The specific heat was measured to be 0.573Jg−1K−1 (92.64calmol−1K−1) at 330K. The thermal conductivity at room temperature was calculated to be 0.74Wm−1K−1, 1.00Wm−1K−1, and 0.67Wm−1K−1 along the a-, b- and c-axis, respectively. It was found that thermal conductivity increases with increasing temperature, which indicates a glass-like behavior.

Synthesis and negative thermal expansion property of Y2−xLaxW3O12 (0≤x≤2)

Y2−xLaxW3O12 solid solutions were successfully synthesized by the solid state reaction method. The microstructure, hygroscopicity and thermal expansion property of the resulting samples were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and thermal mechanical analysis (TMA). Results indicate that the structural phase transition of the Y2−xLaxW3O12 changes from orthorhombic to monoclinic with increasing substituted content of lanthanum. The pure phase can form for 0≤x≤0.4 with orthorhombic structure and for 1.5≤x≤2 with monoclinic one. High lanthanum content leads to a low relative density of Y2−xLaxW3O12 ceramic. Thermal expansion coefficients of the Y2−xLaxW3O12 (0≤x≤2) ceramics also vary from −9.59×10−6K−1 to 2.06×10−6K−1 with increasing substituted content of lanthanum. The obtained Y0.25La1.75W3O12 ceramic shows almost zero thermal expansion and its average linear thermal expansion coefficient is −0.66×10−6K−1 from 103°C to 700°C.

Growth and characterization of Nd:LGGG laser crystal

A Nd:(LuxGd1−x)3Ga5O12 (Nd:LGGG) crystal with dimensions of Ф 26×14mm3 was successfully grown by the Czochralski (Cz) method. The effective segregation coefficients of the Nd and Lu ions in the crystal were measured to be 0.50 and 1.32, respectively. The thermal properties of the crystal, including the average linear thermal expansion coefficient, specific heat and thermal diffusion coefficient, were measured, and the thermal conductivity was calculated. The Judd–Ofelt theory was applied to calculate the spectral parameters of the crystal. All the properties show that the Nd:LGGG crystal is a promising material for laser applications.

Crystal structure and thermal expansion of aragonite-group carbonates by single-crystal X-ray diffraction

Crystal structures of four aragonite-group carbonates-aragonite (Ca 0.997 Sr 0.003 CO 3 ), calcian strontianite (Ca 0.147 Sr 0.853 CO 3 ), cerussite (Ca 0.001 Pb 0.999 CO 3 ), and witherite (Sr 0.019 Ba 0.981 CO 3 )-have been refined at ambient conditions, and thermal expansion has been measured over a range of temperatures from 143 to 586 K by single-crystal X-ray diffraction. Average linear thermal expansion coefficients α 0 (V) are 58(2), 58.3(7), 64(2), and 57(2) (× 10 −6 K −1 ) for aragonite, strontianite, cerussite, and witherite, respectively, throughout the experimental temperature range. Aragonite, strontianite, and witherite have very similar α 0 (V) values, whereas that of cerussite is significant larger, primarily due to the caxis thermal expansion for cerussite being much larger than those of the other carbonates. There are no significant differences for α 0 (a) values among the four carbonates, whereas α 0 (b) values decrease in the order of aragonite > strontianite > cerussite ≈ witherite, and α 0 (c) values increase in the order of aragonite < strontianite < witherite < cerussite. Crystal structures were refined for aragonite (184 to 527 K). <Ca-O> vs. T (K) is fitted linearly quite well, with a slope of 5.8(8) × 10 −6 (Å/K). Corrected for assumed rigid body motion, the CO 3 groups showed no significant change in C-O distances over the temperature range.

Thermomechanical Analysis of (Cu0.5Tl0.5)-1223 Substituted by Pr and La

The thermomechanical analysis (TMA) of Cu0.5Tl0.5Ba2a2−xRxCu3O10−δ, where R=Pr and La, with 0.0≤x≤0.15, was carried out in temperature range from 450 to 1145 K. The samples were prepared by single-step solid state reaction technique. The prepared samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The superconductivity of the prepared samples was investigated by electrical resistivity measurement. The results showed that low substitution content enhanced the (Cu0.5Tl0.5)-1223 phase formation, while the higher substitution content degraded this phase. The higher superconducting transition temperatures Tc were found to be 114 K and 109 K at x= 0.025 for Pr- and La-substitutions, respectively The average linear thermal expansion coefficient increased as x increased, while the shrinkage temperature decreased as x increased. Those results were emphasized by porosity and Vickers microhardness calculations. Debye temperature θD was calculated from the linear thermal expansion coefficient data and correlated to Tc to estimate the electron-phonon coupling λep.

Anisotropic thermal properties of the polar crystal Cs2TeMo3O12

A Cs2TeMo3O12 single crystal with dimensions of 17mm×17mm×18mm was grown using the top-seeded solution growth method. Thermal properties, including thermal expansion, specific heat, thermal diffusivity and thermal conductivity, were investigated as a function of temperature. The average linear thermal expansion coefficients along different crystallographic directions were measured to be αa=7.34×10−6K−1 and αc=32.02×10−6K−1 over the temperature range of 30–430°C. The specific heat was measured to be 0.400–0.506Jg−1K−1 from 22°C to 440°C. The thermal conductivity was calculated to be 1.86 and 0.76Wm−1K−1 at 22°C along the a and c axes, respectively. With increasing temperature from 22 to 430°C, the thermal conductivity decreases by 33.0% along the a axis, while it decreases by 18.5% below 200°C and then remains unchanged along the c axis. The relationship between structure and the thermal properties is also discussed.

Characterization of Disordered Melilite ${\rm Nd}{:}{\rm SrLaGa}_{3}{\rm O}_{7}$ Crystal

A disordered Nd:SrLaGa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> (Nd:SLGM) laser crystal was grown by the Czochralski method. The thermal properties, including the average linear thermal expansion coefficient, thermal diffusivity, specific heat, and thermal conductivity were measured. Thermal conductivity values along the - and -axes were found to be 1.95 and 1.70 W m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , respectively, near 30°C, neither of which are as high as the previously reported value of 11 W m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . It was found that the thermal conductivity increases with increasing temperature, which is similar to the behavior of glass. The polarized absorption and emission spectra were measured at room temperature, and Judd-Ofelt analysis was carried out to calculate the fluorescence branching ratios and the fluorescence lifetime. The stimulated emission cross-section for the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3/2</sub> → <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11/2</sub> transition was calculated to be 1.0×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-19</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Finally, a diode-pumped laser experiment at 1.06 μm was performed. The highest peak power achieved was 1.16 W with an optical slope efficiency of 11%. The results indicate that Nd:SLGM is a promising material for use as disordered laser medium.

Synthesis and tunable thermal expansion property of Al 2−δSc δW 3O 12

A series of solid solutions of Al 2−δSc δW 3O 12 ( δ = 0–2) were successfully synthesized by the solid-state reaction with aluminum oxide, scandium oxide and tungsten trioxide as raw materials. The phase composition and structure of the products were analyzed by X-ray powder diffraction and scanning electron microscopy, while the linear thermal expansion coefficients were measured by thermo dilatometer. The results indicate that Al 2−δSc δW 3O 12 with high purity can be successfully prepared by the solid-state method. All samples of different δ values crystallize in the same orthorhombic structure with space group of Pnca. The lattice constants and cell volume increase linearly with increasing Sc content. The average linear thermal expansion coefficients of Al 2−δSc δW 3O 12 measured by thermo dilatometer indicate that the thermal expansion coefficients of the solid solutions could be adjusted to the desired values, such as positive, near zero or negative by simply changing the δ value.

Growth and characterization of Nd-doped disordered Ca3Gd2(BO3)4 crystal

A high-quality disordered Nd3+:Ca3Gd2(BO3)4 (Nd3+:CGB) laser crystal was grown by the Czochralski method. The space group and effective segregation coefficient of Nd3+ were determined to be Pnma and 1.06, respectively. The thermal properties, including the average linear thermal expansion coefficient, thermal diffusivity, specific heat, and thermal conductivity were systematically measured for the first time. It was found that the thermal conductivity increases with increasing temperature, indicating glasslike behavior. The polarized spectral properties of the crystal were investigated, including the polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay. The spectroscopic parameters of Nd3+ ions in Nd3+:CGB crystal have been obtained based on Judd–Ofelt theory. The anisotropy of the spectral properties for different polarized directions was discussed. Additionally, the continuous-wave (CW) laser performance at 1.06 μm was demonstrated for the first time. The maximum output power of 603 mW was achieved with corresponding optical conversion efficiency of 8.33% and slope efficiency of 9.95%.

Synthesis, structure, and thermal expansion of sodium zirconium arsenate phosphates

Sodium zirconium arsenate phosphates NaZr2(AsO4)x(PO4)3−x were synthesized by precipitation technique and studied by X-ray diffraction and IR spectroscopy. In the series of NaZr2(AsO4)x(PO4)3−x, continuous substitution solid solutions are formed (0 ≤ x ≤ 3) with the mineral kosnarite structure. The crystal structure of NaZr2(AsO4)1.5(PO4)1.5 was refined by full-profile analysis: space group R\(\bar 3\)c, a = 8.9600(4)A, c = 22.9770(9) A, V = 1597.5(1) A3, Rwp = 4.55. The thermal expansion of the arsenate-phosphate NaZr2(AsO4)1.5(PO4)1.5 and the arsenate NaZr2(AsO4)3 was studied by thermal X-ray diffraction in the temperature range of 20–800°C. The average linear thermal expansion coefficients (αav = 2.45 × 10−6 and 3.91 × 10−6 K−1, respectively) indicate that these salts are medium expansion compounds.

Negative Thermal Expansion of Tm&lt;sub&gt;2&lt;/sub&gt;Fe&lt;sub&gt;15&lt;/sub&gt;SiCr Compound

The thermal expansion and the Curie temperature of Tm2Fe15SiCr compound have been investigated by means of x-ray diffraction and magnetization measurements. The result shows that the Tm2Fe15SiCr compound has a hexagonal Th2Ni17-type structure. One Cr and one Si atoms substituting for two Fe atoms can increase the Curie temperature obviously. In magnetic state, an anisotropic anomalous thermal expansion was observed. Along the c-axis, the average linear thermal expansion coefficient αc=-2.04×10-5/K in the temperature range 303-460K. Along the a-axis, the average linear thermal expansion coefficient αa=-8.09×10-5/K in 370-410K. In the temperature range 370-450K, the average volume thermal expansion coefficient αv =-2.08×10-5/K. The mechanism of the thermal expansion anomaly of Tm2Fe15SiCr compound was discussed in this paper.

Negative Thermal Expansion of Gd&lt;sub&gt;2&lt;/sub&gt;Fe&lt;sub&gt;16.5&lt;/sub&gt;Cr&lt;sub&gt;0.5&lt;/sub&gt; Compound with Th&lt;sub&gt;2&lt;/sub&gt;Ni&lt;sub&gt;17&lt;/sub&gt;-Type Structure

The thermal expansion and the Curie temperature of Gd2Fe16.5Cr0.5 compound have been investigated by means of x-ray diffraction and magnetization measurements. The result shows that the Gd2Fe16.5Cr0.5 compound annealed at 1243°C has a hexagonal Th2Ni17-type structure. Cr atom substituting for Fe atom can increase the Curie temperature obviously. In magnetic state, an anisotropic anomolous thermal expansion was observed. Along the c-axis, the average linear thermal expansion coefficient αc=-2.79×10-6/K in the temperature range 294-472K, and αc =-3.09×10-5/K in 472-592K. Along the a-axis, the average linear thermal expansion coefficient αa =9.22×10-6/K in 294-552K, and αa =-1.41×10-5/K in 552-592K. In the temperature range 472-592K, the average volume thermal expansion coefficient αv =-2.14×10-5/K. The mechanism of the thermal expansion anomaly of Gd2Fe16.5Cr0.5 compound was discussed in this paper.

Structure and properties of ternary manganese nitride Mn 3CuN y thin films fabricated by facing target magnetron sputtering

Deposition of Mn 3CuN y thin films on single crystal Si (1 0 0) at various substrate temperatures ( T sub) by facing target magnetron sputtering is reported. The crystal structure and composition were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results confirmed that the crystalline antiperovskite Mn 3CuN y thin film with (2 0 0) highly preferred texture had been obtained at T sub = 180 °C. Furthermore, for the resulting Mn 3CuN y thin film, it showed different properties compared with the bulk counterpart. There was a paramagnetic to ferrimagnetic transition at 225 K with decreasing temperature. The change of the lattice constant with temperature presented positive thermal expansion behavior and no structural transition was observed. The average linear thermal expansion coefficient ( α) is 2.49 × 10 −5 K −1 from 123 K to 298 K. More interestingly, the temperature dependence of resistivity displayed a semiconductor-like behavior, i.e. an obvious monotonous decrease of resistivity with increasing temperature.

Bulk crystal growth and characterization of a new polar polymorph of BaTeMo2O9: α-BaTeMo2O9

Bulk single crystals of α-BaTeMo2O9 with dimensions up to 51 × 30 × 20 mm3 were grown successfully by a top-seeded solution growth (TSSG) method using TeO2-MoO3 mixture as a flux. High-resolution X-ray diffraction measurement on the (400)-faced plate indicates that the full-width at half-maximum (FWHM) of the rocking curve is 16.55′′. The as-grown crystal exhibits {010}, {002}, {110}, {111} and {201} facets, which are in good accordance with the predicted growth morphology based upon the Bravais-Friedel and Donnay-Harker (BFDH) method. In addition, thermal properties including thermal expansion, specific heat, thermal diffusivity and thermal conductivity were investigated as a function of temperature. The average linear thermal expansion coefficients along the a-, b-, and c-axis from 30 °C to 500 °C were measured to be αa = 9.10 × 10−6 K−1, αb = 19.58 × 10−6 K−1 and αc = 11.94 × 10−6 K−1, respectively. The specific heat was measured to be 0.433–0.566 J (g K)−1 over the temperature range of 30–540 °C. The thermal conductivity along the a-axis is larger than those along other directions (κa>κb> κc). The transmission spectra and refractive indices were also measured. The α-BaTeMo2O9 crystal exhibits a wide transmission window ranging from 380 nm to 5530 nm. The large birefringence of α-BaTeMo2O9 (Δn = 0.305 for light at 404.7 nm) indicates that it is not only Type I and II phase-matchable, but also a very promising candidate for optical devices.

Thermal expansion and elasticity of PdFe3N within the quasiharmonic approximation

We have explored the bulk modulus and the thermal expansion of PdFe3N (space group \(Pm\overline 3 m\)) using ab initio phonon dynamics within the quasiharmonic approximation in the temperature range from 50 to 1000 K. PdFe3N possesses a linear thermal expansion coefficient common for typical ceramics. The calculated average linear thermal expansion coefficient of 6.4 × 10-6 K-1 is consistent with the average measured coefficient of 6.7 × 10-6 K-1. We have shown here that the thermal behavior of this compound can be understood based on the electronic structure and the lattice dynamics thereof. PdFe3N exhibits both metallic as well as covalent-ionic bonding. The Fe–N covalent-ionic bonding suppresses the lattice vibrations of the PdFe3 matrix. The bulk modulus of 188 GPa for PdFe3N decreases by 15% in the temperature range studied, which is expected due to presence of stiff Fe–N bonds.

Synthesis, growth, and characterization of Nd-doped SrGdGa3O7 crystal

A disordered Nd:SrGdGa3O7 (Nd:SGGM) laser crystal was grown by the Czochralski method. The space group and effective segregation coefficient of Nd3+ were determined to be P4¯21m and 1.36, respectively. Thermal properties, including the average linear thermal expansion coefficient, thermal diffusivity, specific heat, and thermal conductivity were measured. It was found that the thermal conductivity increases with increasing temperature, indicating glasslike behavior. Sellmeier’s equations were fitted by measuring the refractive indices in the range of 253–2325 nm. The polarization absorption and emission spectra were measured at room temperature, and Judd–Ofelt analysis was carried out to calculate the fluorescence branching ratios from the upper F43/2 state and the fluorescence lifetime. The stimulated emission cross section for the F43/2→I411/2 transition was calculated to be 2.00×10−20 cm2. Finally, a diode-pumped laser experiment at 1.06 μm is described. Thermal, optical, and laser properties have shown that Nd:SGGM crystals are promising for use as disordered laser materials.

Crystal structure, electrical conductivity and thermal expansion of Nd1–xCaxCoO3–δ (0≤x≤0·5)

The synthesis, crystal structure, thermal expansion and electrical conductivity of the ceramic oxide materials (Nd1–xCax)CoO3 (0≤x≤0·5) were investigated. These powders with perovskites structure were synthesized using the sol–gel method. Compositions have a pure orthorhombic structure up to 0·3 Ca doping. The lattice parameters were determined at room temperature (RT) by powder X-ray diffraction. Thermal expansion measurements on the sintered samples were carried out from RT to 900°C. The average linear thermal expansion coefficient range was found to decrease with increasing Ca doping up to x=0·4 and thereafter it increased. The thermal expansion curves for all values of x displayed rapid increase in slope at high temperatures. Electrical DC conductivity measurements were taken from RT to 600°C. The conductivity of the samples increased with Ca concentration up to 0·3.