Thermal Properties Of Crystals Research Articles

Elastic, thermal and spectral properties of Yb3+:CaSrAl2SiO7 laser crystal

Elastic and thermal properties of CaSrAl2SiO7 crystal have been simulated theoretically. Mechanical and thermal properties of the crystal have been found better than those of Ca2Al2SiO7 with the same crystal structure. An Yb3+:CaSrAl2SiO7 single crystal has been grown by the micro-pulling-down method. Detailed spectral properties of the Yb3+:CaSrAl2SiO7 have been investigated. All the results indicate that the Yb3+:CaSrAl2SiO7 is a potential material for Yb3+ laser, especially for tunable and ultrashort lasers.

The Important Thermal and Kinetic Properties of Crystals and Their Calculations with the Use of the Gibbs Potentials

In this work, the important thermal and kinetic characteristics of crystals are calculated. It was shown that in a state of thermodynamic equilibrium, the thermal properties of crystals are additive, and their value for an entire crystal is calculated by summing the values of thermal properties of the crystal lattice and the properties of the gas of free charge carriers in a crystal. These properties are fully characterized by the appropriate Gibbs potentials. In this work it was also shown that when the electric field E and temperature gradient ΔrT are created in a crystal, and this crystal is placed in the magnetic field with the magnetic inductance vector B, then there the electric charge and heat transport processes begin to exist in the crystal. These processes are described by the generalized electric and heat conduction equations. The tensors and the scalar coefficients in these equations – these are the kinetic properties of the crystals. They describe the nature of their actual properties and they have widespread and pragmatic applications in modern solid-state electronics

Unified theory of thermal transport in crystals and disordered solids

Crystals and glasses exhibit fundamentally different heat conduction mechanisms: the periodicity of crystals allows for the excitation of propagating vibrational waves that carry heat, as first discussed by Peierls; in glasses, the lack of periodicity breaks Peierls' picture and heat is mainly carried by the coupling of vibrational modes, often described by a harmonic theory introduced by Allen and Feldman. Anharmonicity or disorder are thus the limiting factors for thermal conductivity in crystals or glasses; hitherto, no transport equation has been able to account for both. In the paper https://arxiv.org/abs/1901.01964, we derive such equation, resulting in a thermal conductivity that reduces to the Peierls and Allen-Feldman limits, respectively, in anharmonic-and-ordered or harmonic-and-disordered solids, while also covering the intermediate regimes where both effects are relevant. This approach also solves the long-standing problem of accurately predicting the thermal properties of crystals with ultralow or glass-like thermal conductivity, as we show with an application to a thermoelectric material representative of this class. This database contains the raw data related to the images reported in the paper https://arxiv.org/abs/1901.01964.

Study on growth, spectral, optical and thermal characterization of an NLO crystal: 6-Methyl nicotinic acid (6MNA)

6-methyl-nictinic acid (6MNA), organic non linear optical (NLO) single crystals were grown by slow evaporation solution technique. The cell parameters of 6MNA were confirmed from single crystal X-ray diffraction analysis. The Fourier transforms infrared and proton Nuclear magnetic resonance spectral analysis confirm the presence of various functional groups and the placement of protons respectively in 6MNA compound. UV–vis–NIR spectral studies revealed that the grown 6MNA has good optical transmission in the range of entire visible region. The thermal properties of crystals were evaluated from thermogravimetric (TG) and differential thermal analysis (DTA). It has shown that the grown crystals were stable up to 213°C. The second harmonic generation (SHG) measurements indicated that the efficiency of 6MNA is two times greater than that of the KDP crystals and is suitable for frequency conversion applications.

Thermal and Optical Properties of Glycine Crystals with Additives of Nitrates

Semi-organic crystals of Glycine Sodium nitrate Calcium nitrate (GSC) with two different molar ratios were grown using slow evaporation technique. Crystals of size 22 × 16 mm were obtained within time period of 3-4 weeks at ambient temperature. The compositional study and purity of the crystals were determined using Energy Dispersive X-ray Analysis (EDAX) and CHN Analyzer. Surface of the crystals was studied at micrometer scale with optical microscopy. These crystals were characterized by powder X-ray diffraction and indexing of diffraction pattern was done based on monoclinic system. We also studied thermal properties of these crystals using TGA/DTA/DTG analysis. From UV-Vis spectra we could observe wide transparency window from these crystals in the visible region, which can be useful for opto-electronic applications.

Method of a Generalized Physical Property in the Crystal Physics Problems

A method is proposed for determining the crystallographic directions in crystals of various point symmetry, along which the combination of physical properties of various ranks and Curie symmetry gets a predetermined value. The method is demonstrated for the combination of the second-rank tensors describing optical and thermal properties of crystals of the monoclinic system. The possibility of using the proposed method for the physical properties of high ranks is demonstrated.

Structural, optical, thermal, photoconductivity, laser damage threshold and fluorescence analysis of an organic material: β-P-amino benzoic acid single crystal

β-P-amino benzoic acid, an organic single crystal was grown by slow evaporation technique. Single crystal X-ray diffraction studies show that the grown crystal has β-polymorph of P-amino benzoic acid [β-PABA] form and the lattice parameters are a=6.30Å, b=8.61Å, c=12.43Å α=γ=90° and β=100.20°. FTIR analysis confirms that bands at 1588cm−1, 1415cm−1 are assigned to ring skeletal vibrations of title compound. The molecular structure of the grown crystal has been identified by Nuclear Magnetic Resonance spectral study. The optical absorbance spectrum from 200 to 1100nm shows that there is an edge absorbance in UV region. Optical band gap of the crystal has been assessed from the absorbance spectrum. The thermal properties of crystals were evaluated from TG-DTA analysis, it exhibits that there is no weight loss up to 187°C. Laser damage threshold indicates that the grown crystal has no surface damage up to 35mJ. Photoconductivity and fluorescence spectral experiments are also carried out and the results are discussed.

Crystal structure, spectroscopic investigation and thermal properties of l-lysine p-toluenesulfonate

A novel organic crystal was prepared from l-lysine (Lly) and p-toluenesulfonic acid (pTS), which was grown from an aqueous solution by slow cooling method. The crystal system and the lattice parameters have been confirmed by single crystal X-ray diffraction studies. The FT-IR, FT-Raman, 1H-NMR and 13C-NMR spectral of the crystal have been recorded and analyzed. The spectral analyses confirmed the presence of various functional groups and the molecular configurations in LLTS crystal. The UV-Vis-NIR transmittance spectrum has been carried out which shows the cutoff wavelength around 280 nm. The thermal properties of crystal have been evaluated from thermogravimetric (TG) and differential thermal analysis (DTA). The melting point of grown crystal is fairly high, at around 259 °C. The nonlinear optical (NLO) properties of LLTS crystal were demonstrated by powder SHG experiment and also by quantum chemical calculations. The powder SHG efficiency of LLTS crystal is relatively low and very different from theoretical calculation results.

Investigation on growth, structure and characterization of succinate salt of 8-hydroxyquinoline: An organic NLO crystal

8-Hydroxyquinolinium succinate (8-HQSU) has been synthesized and single crystals were grown from ethanol solvent by employing the technique of slow evaporation at room temperature. The structure of the grown crystal has been elucidated by single crystal X-ray diffraction analysis. It reveals that 8-HQSU crystallizes in monoclinic system with non-centro symmetric space group P21. FTIR, 1H and 13C NMR spectral investigations have been carried out to identify the vibrational modes of various functional groups and placement of proton and carbon in the 8-HQSU compound, respectively. UV–vis–NIR transmission spectrum shows the cutoff wavelength around 357nm. In addition, a photoluminescence spectral analysis was carried out for 8-HQSU crystals. The thermal properties of crystals were evaluated from TGA and DTA techniques and the crystal was found to be stable up to 145°C. The dielectric studies show that the dielectric constant and dielectric loss decrease exponentially with frequency at different temperatures. Photoconductivity studies were carried out on the grown crystals it reveals the positive photo conducting nature. Powder second harmonic generation property of the crystal was confirmed by Kurtz and Perry powder SHG technique and it is found to be 1.3 times greater than that of KDP.

Investigation of the structure and properties of (K x (NH4)1 − x )3H(SO4)2 single crystals

The influence of isomorphous replacement in the cation sublattice on the kinetics of the phase transition in single crystals of the solid solutions (Kx(NH4)1 − x)mHn(SO4)(m + n)/2 · yH2O belonging to the K3H(SO4)2-(NH4)3H(SO4)2-H2O salt system was studied. Superproton phase transitions for the end compositions of this system have been found earlier. The optical and thermal properties of crystals with the composition (K,NH4)3H(SO4)2 in the temperature range from 295 to 500 K were investigated, and the crystal structure was determined at 295 K. The results of the study and the comparison with the literature data show that the replacement of potassium atoms with ammonia leads to a fundamental change in the kinetics of the phase transition, the phase-transition temperature remaining virtually unchanged.

Growth, thermal and spectral properties of Tm3+, Ho3+ co-doped NaGd(MoO4)2 Crystal

A Tm3+/Ho3+:NaGd(MoO4)2 crystal was grown by the Czochralski method. The XRD results matched standard data from JCPDS file, which accorded with scheelite structure with an I41/a space group. Thermal properties of crystal were analyzed by using the TG–DSC curve. The melting point and specific heat are 1182°C and 0.5J/gK at 300K, respectively. The Spectral properties of the Tm3+/Ho3+:NaGd(MoO4)2 crystal were investigated, including room temperature absorption spectrum and fluorescence spectrum. The absorption cross-section of Tm3+ at 796nm is 4.33×10−20cm2 with pertinent full widths at half maximum (FWHM) of 10nm. The intensity parameters, spontaneous emission probability, fluorescence branching ratios and radiative lifetimes were calculated by Judd–Ofelt theory. The emission cross-sections are 1.47×10−20cm2 and 1.36×10−20cm2 for Tm3+ at 1850nm and Ho3+ at 2000nm respectively. The lifetime of 5I7→5I8 (Ho3+) was 4.263ms.

Control of crystallographic orientation in diamond synthesis through laser resonant vibrational excitation of precursor molecules.

Crystallographic orientations determine the optical, electrical, mechanical, and thermal properties of crystals. Control of crystallographic orientations has been studied by changing the growth parameters, including temperature, pressure, proportion of precursors, and surface conditions. However, molecular dynamic mechanisms underlying these controls remain largely unknown. Here we achieved control of crystallographic orientations in diamond growth through a joint experimental and theoretical study of laser resonant vibrational excitation of precursor molecules (ethylene). Resonant vibrational excitation of the ethylene molecules using a wavelength-tunable CO2 laser steers the chemical reactions and promotes proportion of intermediate oxide species, which results in preferential growth of {100}-oriented diamond films and diamond single crystals in open air. Quantum molecular dynamic simulations and calculations of chemisorption energies of radicals detected from our mass-spectroscopy experiment provide an in-depth understanding of molecular reaction mechanisms in the steering of chemical reactions and control of crystallographic orientations. This finding opens up a new avenue for controlled chemical vapor deposition of crystals through resonant vibrational excitations to steer surface chemistry.

Dislocation dynamics during plastic deformations of complex plasma crystals

The internal structures of most periodic crystalline solids contain defects. This affects various important mechanical and thermal properties of crystals. Since it is very difficult and expensive to track the motion of individual atoms in real solids, macroscopic model systems, such as complex plasmas, are often used. Complex plasmas consist of micrometer-sized grains immersed into an ion-electron plasma. They exist in solidlike, liquidlike, and gaseouslike states and exhibit a range of nonlinear and dynamic effects, most of which have direct analogies in solids and liquids. Slabs of a monolayer hexagonal complex plasma were subjected to a cycle of uniaxial compression and decompression of large amplitudes to achieve plastic deformations, both in experiments and simulations. During the cycle, the internal structure of the lattice exhibited significant rearrangements. Dislocations (point defects) were generated and displaced in the stressed lattice. They tended to glide parallel to their Burgers vectors under load. It was found that the deformation cycle was macroscopically reversible but irreversible at the particle scale.

Synthesis, growth, structural, optical and thermal properties of an organic single crystal: 4-Nitroaniline 4-aminobenzoic acid

The organic single crystals of 4-nitroaniline 4-aminobenzoic acid (4NAABA) were grown from ethanol solvent. The lattice parameters of the grown crystal have been confirmed from single crystal XRD analysis. The powder XRD pattern shows the various planes of grown crystal. The FTIR and 1H NMR spectral analysis confirm the presence of various functional groups and the placement of proton in 4NAABA compound respectively. The UV absorption was carried out which shows the cutoff wavelength around 459nm. The optical band gap of the crystal has been evaluated from the transmission spectra and absorption coefficient by extrapolation technique. In addition, a fluorescence spectral analysis is carried out for 4NAABA crystals. The thermal properties of crystals were evaluated from thermogravimetrical analysis. It shows that the grown crystal is stable up to 160°C and the crystal has sharp melting point at 151°C.

Compressibility and Moelwyn-Hughes Parameter of NaI crystals under high pressure, as the function of thermal properties

The credit for the commencement of inter ionic potential function goes to Born and Lande, one of whose milestone has been their expression into inverse function. Similarly, Born and Mayer also proposed the exponential function of the potential for the repulsive component. However none of them could get the desired success. Subsequently, many more prominent scientists devoted their effort towards these thermal properties of the crystals, among which the endeavour of Jha and Thakur cannot be overlooked, who proposed a new interionic function to observe the properties of ionic crystal under high pressure. During its formulation they included both an inverse power function due to Born and Lande and an exponential function due to to Born and Mayer. Appreciably, Jha and Khan used it for studying the hyped thermal properties of NAI and CsI crystal under high pressure up to 100 Kilo bar. DOI: http://dx.doi.org/10.3126/bibechana.v9i0.7180 BIBECHANA 9 (2013) 88-91

Spectroscopic and thermal properties of Yb doped CaF2-SrF2 laser crystal

Yb: CaF2-SrF2 crystals are grown by Bridgman technique. The spectroscopic properties, thermal diffusion coefficients and thermal expansion coefficients at different temperatures are studied. Thermal conductivity at 300 K and thermal expansion coefficient are calculated. The absorption spectra, fluorescence spectra, thermal properties of crystals are analyzed by comparison method. The results show that the absorption and emission cross sections are larger in the high concentration SrF2 disordered crystal. And also the emission cross section is large and wide at 1040 nm in the Yb: CaF2-SrF2 (19%) crystal. It demonstrates that for different ratios of CaF2 and SrF2 in the disordered crystals, the spectroscopic properties are different. The main possible reason is the different disorders, low symmetry, low symmetry optical centers in the disordered crystal. It can also be seen that the disordered crystal has a good thermal conductivity.

Molecular dynamics study of a one component soft-core system: thermodynamic properties in the crystalline state

In the present work, molecular dynamics (MD) simulations have been performed to study thermal properties of crystals in a one component soft-core system. The system was examined along the phase-diagram using the compressibility factor, P[combining tilde](T*) ≡PV/NkBT plotted against the reduced density ρ* (or reduced temperature, T*). The specific heat, CV, of the system is presented as the function of P[combining tilde](ρ*) and also as the function of the reduced potential energy, U*. These CV values are expressed using coefficients of the expansion around the harmonic term. We also derived the expression for entropy using these coefficients. The contribution of an anharmonic term in the specific heat and entropy was clarified by this. These results are compared with those obtained from the fluctuation of kinetic energy. Several quantities related to the distribution of time dependent reduced temperature and dynamical compressibility factor (PV/NkBT)t are also examined and three T* regions of thermal behaviors are characterized. In the diagram, the glass transition by cooling or compression can be treated on the same basis. Results of the present work will be helpful for a better understanding of the changes in the specific heat during the glass transition in the future works.

Synthesis, Growth and Characterization of 4-Benzeneazoaniline Single Crystal

A new organic nonlinear optical material 4-Benzeneazoaniline (C12H11N3) was synthesized by diazotization and diazocoupling mechanisms. Single crystal of 4-Benzeneazoaniline was grown by slow evaporation of methanol solution at room temperature. Transparent crystals with size up_to 13x4x4 mm 3 were obtained. Single crystal X-ray diffractometer was utilized to measure the unit cell parameters and to confirm the crystal structure. The structure of compound was further confirmed by FTIR, 1 H & 13 C NMR and mass spectral analyses. The UV-Vis-NIR result shows that the crystal has a sharp cut off at 220 nm and is nearly 75% transparent over a wide wavelength range enabling it for application in the UV region. The optical energy gap of 4Benzeneazoaniline was found to be 3.4 eV. Thermal properties of crystals were investigated using thermogravimetric and differential scanning calorimetric analyses, which indicated that the material does not decompose before melting. The NLO test confirms the second harmonic signal generation in the sample.

A study of the optical and thermal properties of nonlinear mercury thiogallate crystals

The technology of growing mercury thiogallate crystals (HgGa2S4) is improved and high-quality bulk samples are produced. The basic optical and thermal properties of these crystals are studied. The transmission spectra of mercury thiogallate are measured and its nonlinear characteristics such as the quadratic susceptibility, tuning curves, and the optical-damage resistance are also determined. The specific heat and thermal conductivity of HgGa2S4 are measured. It is concluded that the combined properties of HgGa2S4 crystals can provide for them a leading position among the materials used in nonlinear-optical devices for mid-IR-frequency conversion.

Strongly correlated bistable sublattice and temperature hysteresis of elastic and thermal crystal properties

It is shown that in crystal lattices with a basis the cooperative behavior of a certain type of atoms performing optical long-wavelength vibrations in a double-well potential of the field of the matrix lattice may lead to the formation of a bistable sublattice. As a result of the interaction of the metastable states of such a sublattice with the vibrational states of the matrix lattice, the elastic and thermal properties of the crystal acquire anomalous, hysteresis-like, temperature curves. The concepts developed in the paper make it possible to obtain a qualitative interpretation, which agrees with the experimental data, of the hysteresis-like temperature dependence of the speed and absorption of ultrasonic waves, the specific heat, and the thermal conductivity in superconducting yttrium and bismuth cuprates.