Donald Schuele

Pressure and temperature derivatives of the elastic constants of caF2 and BaF2

Abstract The elastic constants and their pressure and temperature derivatives were measured by the ultrasonic pulse-echo technique for CaF 2 and BaF 2 at 195° and 298°K. The elastic constants and the pressure derivatives were analyzed in terms of a dipole shell model due to Axe. The Gruneisen parameter in the low temperature limit was calculated and found to compare favorably with the Gruneisen parameter determined from thermodynamic data. The explicit temperature dependencies of the normal mode frequencies for the non-dispersive acoustic modes were calculated. The ultrasonic equation of state is determined and compared with Bridgmans compression data.

Low‐frequency dielectric constants of α‐quartz, sapphire, MgF2, and MgO

The 1000‐Hz 300°K dielectric constants were measured for crystalline α‐quartz, sapphire, MgF2, and MgO, and polycrystalline sapphire (Lucalox), magnesium fluoride (IRTRAN 1), and magnesium oxide (IRTRAN 5). The measurements were performed using the method of substitution (two‐fluid method). The results are as follows: single‐crystal α‐quartz, es∥=4.6368±0.001 and es⊥=4.5208±0.001; single‐crystal sapphire, es∥ = 11.589±0.005 and es⊥=9.395±0.005; polycrystalline sapphire (Lucalox), es=10.154±0.007; single‐crystal MgF2, es∥ =4.826±0.01 and es⊥=5.501±0.01; polycrystalline MgF2 (IRTRAN 1), es=5.289±0.001; single‐crystal MgO, es=9.830 ±0.001; and polycrystalline MgO (IRTRAN 5), es=9.833±0.001, where es∥ and es⊥ are the dielectric constants parallel and perpendicular, respectively, to the c axis.

The pressure derivatives of the elastic constants of lead

Abstract The pressure derivatives of the adiabatic elastic constants of CaFa have been measured at room temperature by the ultrasonic pulse-echo method. The values found are: dc 11 ′/dp dc′/dp dc 44 /dp 6.49 0.847 1.30 where c 11 ′ = (c 11 +c 12 +2c 44 ) 2 , c′ = (c 11 −c 12 ) 2 . The results were used to compute the Gruneisen parameters. The computed low temperature limit of Gruneisen parameter γ L is 1.11, which agrees with Whites value of 1.2 ±0.2 obtained from thermal expansion measurements.

The pressure and temperature derivatives of the elastic constants of AgBr AND AgCl

Abstract The ultrasonic pulse-echo method was used to measure the adiabatic elastic constants and their pressure and temperature derivatives for AgBr and AgCl at 300 and 195°K. The explicit temperature dependence of the elastic constants was calculated, and the value for the isothermal bulk modulus was found to be anomalously large. An ultrasonic equation of state was compared with Bridgmans compression data and the effect of the significantly nonlinear pressure dependence of the bulk modulus of AgBr was shown. High and low temperature limiting values of the Gruneisen parameter were calculated from the elastic data and compared with those calculated from available thermodynamic data.

Accurate Determination of the Dielectric Constant by the Method of Substitution

A substitution method for highly accurate determination of the static dielectric constant of solids is presented along with techniques for refining capacitance measurements. The results for some alkaline earth fluorides are CaF2, 6.799; SrF2, 6.466; and BaF2, 7.359; and an alkali halide KCl is 4.818.

Layer confinement effect on charge migration in polycarbonate/poly(vinylidene fluorid-co-hexafluoropropylene) multilayered films

Forced assembly microlayer coextrusion was used to produce polycarbonate/poly(vinylidene fluoride-co-hexafluoropropylene) [PC/P(VDF-HFP)] layered films for dielectric capacitor applications. Low field dielectric spectroscopy was systematically carried out on the layered films and controls. A low frequency relaxation was found that shifted to higher frequency and decreased in intensity as the P(VDF-HFP) layer thickness was reduced. The interfacial Maxwell-Wagner polarization, being layer thickness independent, could not account for this reduced low frequency relaxation behavior as the layer thickness decreased. Charge diffusion models by Sawada and Coelho, however, satisfactorily predicted the observed layer thickness effect, indicating that the migration of impurity ions in the P(VDF-HFP) layer caused the low frequency relaxation. A new, convenient fitting procedure was developed for the Sawada model yielding an ion concentration and diffusion coefficient of 2 × 1021 ions/m3 and 2 × 10−13 m2/s, respective...

The temperature variation of the dielectric constant of ’’pure’’ CaF2, SrF2, BaF2, and MgO

Improved values of the real part of the low‐frequency dielectric constant are presented for ’’pure’’ CaF2, BaF2, SrF2, and MgO over the temperature range 5.5‐400 K. Accurate measurements of both the real and imaginary parts of the dielectric constant were made so that corrections could be made to allow for dipolar impurities. The final results are thought to be accurate to better than 0.1% over the full range of temperatures.

Effect of OH− on the low‐frequency dielectric constant of vitreous silica

The 1000‐Hz 300°K dielectric constant, es, of 24 kinds of commercially available vitreous silica has been measured to an accuracy of 0.01% and a precision of about 1 part in 300 000 by the method of substitution (two‐fluid technique). The observed dielectric constant ranges from 3.8073 to 3.8304. These results are correlated with hydroxyl ion content and other imperfections. It is found that es=3.8073+2.72×10−22 N where N is the hydroxyl concentration in ions/cm3, and observed deviations from this rule are attributed to metallic impurities and inclusions. From the results it appears that 3.8073 closely approximates the low‐frequency dielectric constant of pure vitreous silica.

Low‐Frequency Dielectric Constants of the Alkaline Earth Fluorides by the Method of Substitution

The 1000‐Hz 300°K dielectric constants of the alkaline earth fluorides were measured to an accuracy of 0.01% by the method of substitution. Reproducibly different values for various crystals of the same type were obtained which varied beyond the experimental error. The ranges of results for various crystals of each type measured along with further separation by manufacturer are: CaF2, Harshaw, 6.7984–6.7988, Optovac, 6.8074–6.8432; SrF2, Harshaw, 6.4647–6.4664, Optovac, 6.4700–6.4703; and BaF2, Harshaw, 7.3590–7.3595, Optovac, 7.3606–7.3630. The spread for each type of crystal is thought to be attributable to random trace impurities.

Low temperature grüneisen parameter of RbI from elasticity data

Abstract The elastic constants and their pressure derivatives of rubidium iodide were measured at 295° and 195°K by the ultrasonic pulse-echo technique. The results are: dC 11 dP dC 12 dP dC 44 dP 295°K 13.16 1.66 −0.51 195°K 12.83 1.78 −0.55 The low temperature Gruneisen parameter was calculated and found to be negative in agreement with that predicted by G.K. White on the basis of thermal expansion data. These results can be understood qualitatively via a simple Born model.