Volume Compressibility of BeO and Other II-VI Compounds

Cline, C.F.; Stephens, D.R.

doi:10.1063/1.1714596

Cited by 131 publications

(31 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The data from our measurements of the ultrasound velocity in samples of BeO of different shape and size (see Tables 1 -4) differed significantly from the calculated and experimental values of other investigators [10,11] (see Table 5). …”

Section: Velocity and Absorption Of Ultrasound In Beryllium Oxide Cercontrasting

confidence: 74%

Velocity and absorption of ultrasound in beryllium oxide ceramic

et al. 2006

View full text Add to dashboard Cite

The ultrasound wave propagation velocity and absorption of ultrasound in samples of beryllium ceramics of varying density, shape, and size that differed by the molding method and degree of texturing of BeO microcrystals were investigated at room and low temperatures (approximately 100 K). It was found that the ultrasound propagation velocity increases with an increase in the density of the samples. It was shown that the ultrasound velocity in beryllium ceramics without specially added dopants is weakly dependent on the frequency in the 5 -25 MHz range.Measuring the velocity and absorption of ultrasound in ceramic materials is revealing ways of creating technical devices for transmission of ultrasound energy with minimum losses in a wide temperature range.Of the oxide ceramic materials, a high-temperature, chemically, thermally, and radiationally resistant beryllium oxide ceramic is drawing great attention. The area of its application in different technical sectors is expanding. Articles made of beryllium ceramic are widely used in special metallurgy (for example, in melts of different metals and salts which have high temperatures, up to 2170 K), atomic, laser, electronics, electrical, and other sectors of industry, and special instrument making (RF patents Nos. 2141120, 2258331, 2248336) [1 -7].Propagation of ultrasound waves in different ceramic materials has been insufficiently investigated. Measurements in different types of oxide ceramics (BeO, Al 2 O 3 , ZrO 2 , MgO, etc.) showed that a dense BeO ceramic has the highest ultrasound velocity. For this reason, studying the features of propagation and absorption of ultrasound in beryllium ceramics at high (up to 2170 K), room, and low temperatures is pressing.The samples for the studies were obtained with ordinary ceramics technology -by semidry compression molding, slip casting (slips on organic base), and extrusion of plastic ceramic mass on organic base. Both the pure ceramic (with no specially added dopants) and ceramic based on BeO with TiO 2 dopants were used for the experiments. Ceramic articles in the form of rods, wafers, disks, and rings of different thickness and density were fabricated.The BeO powder used for fabrication of the ceramic articles was represented by microcrystals of different morphology -primarily in the form of a mixture of idiomorphic hexagonal-prismatic crystals and in a smaller volume, rhombic and tetrahedral habit (see Fig. 1).Using the petrographic method, it was found that in molding articles by semidry compression molding and slip casting, predominant stacking of the microcrystals perpendicular to the applied force (in compression molding) and perpendicular to the gravitational force in slip casting (texturing) is observed. Since most of the BeO microcrystals are spread along polar axis c and differ in properties as a function of the crystallographic direction, anisotropy of their physicochemical properties is established in molding of ceramic articles. The ceramic obtained by extrusion of the ceramic paste differed because the ...

show abstract

Section: Velocity and Absorption Of Ultrasound In Beryllium Oxide Cercontrasting

confidence: 74%

Velocity and absorption of ultrasound in beryllium oxide ceramic

et al. 2006

View full text Add to dashboard Cite

show abstract

“…Under low pressures p (<50 MPa), ÷ » a = 4.13´10 -12 Pa -1 . It can be seen that the discrepancy between the calculated and experimental [16] values is around 20%. Chang and Cohen [15] report the experimental value ÷ = 4.76´10 -12 Pa -1 , whose deviation from our calculation is~5%.…”

mentioning

confidence: 83%

“…According to available experimental data [16], the temperature dependence ÷ is described by the following equation:…”

mentioning

confidence: 99%

First-principle quantum-chemical calculations of several thermomechanical parameters of beryllium ceramics

et al. 2006

View full text Add to dashboard Cite

The first-principle quantum-chemical calculations of elastic constants for beryllium oxide and their approximation (the Voigt -Reuss -Hill model) for a polycrystalline material are used to derive quantitative estimates of several thermomechanical parameters of BeO ceramics: isothermal compression coefficient, sound velocity, the Debye temperature, and coefficients of linear and volume temperature expansion, as well as the temperature dependence of molar heat capacity and thermal conductivity. The results are discussed in correlation to available experimental data.Ceramics based on beryllium oxide have found wide application as functional and structural materials in contemporary instrument engineering [1 -4]. Calculating the service parameters of BeO ceramics by methods of computational quantum theory is of great practical interest, since in the case of success it becomes possible to theoretically simulate a wide class of functional and structural materials based on BeO ceramics and alloyed with various impurities and to predict their physicochemical properties responsible for their service parameters.The present study uses the results of first-principle quantum-chemical calculations of elastic constants of single-crystal BeO and their subsequent approximation for the polycrystalline state and determines several thermomechanical parameters of impurity-free BeO ceramics: isothermal compression coefficient ÷, sound velocity v, Debye temperature È, and coefficients of linear á and volume â temperature expansion, as well as the temperature dependence of molar heat capacity c M (T) and thermal conductivity ë(T).The initial data are the results of our calculations (using the full-potential linear method of augmented plane waves (FLAPW, code WIEN2K [5]) with generalized gradient approximation (GGA) of the exchange-correlation potential [6] of the elastic constants C ij of wurtzite-type BeO. These values correlated with available experimental data are given in Table 1. The discrepancy between the calculated and measured C ij values ranges from 10 to 22%. It should be taken

show abstract

“…The high-pressure behavior of this compound has attracted continuous interest over the last three decades. In the early studies at room temperature, a phase transition was observed around 3.5 GPa, by optical absorption [1], electrical resistance [2], volume change [3,4] and X-ray diffraction [5 to 8] measurements. The highpressure phase was identified as having a rock-salt structure being stable up to a pressure of % 10 GPa [7 to 10].…”

Section: Introductionmentioning

confidence: 99%