Thermal expansion, measurement

Thermal Expansion Measurement. Thermal expansion measurements were made with a laser interferometer dilatometer (2Q) with a strain resolution of approximately 2x10 6. The temperature cycle for all tests went from room temperature to a maximum of 121°C (except where noted), down to -157°C and back to room temperature. Thermal strain data were taken at approximately 20°C increments with a 30-minute hold at each temperature to allow the specimen and interferometer to reach thermal... 

Kadomtseva et al. (2000) measured thermal expansion and longitudinal and transverse magnetostriction in pulsed magnetic fields up to 25 T in Lai - Sr MnOj single crystals (x = 0.1,0.125 and 0.15). The results were ascribed to a suppression of the O phase and field-induced transitions to a new orbital-ordered ferromagnetic state. 

USEFUL MEASURABLES THERMAL EXPANSIVITY, HEAT CAPACITY, JOULE-THOMSON COEFFICIENT... 

The lattice parameter at room temperature is 0.541134 nm. A reasonable agreement between the results of measured thermal expansion of pure stoichiometric Ce02 up to 1000 C is found. and my conclusion is that the linear thermal expansion coefficient (TEC) is ... 

Measured thermal expansions for heating and cooling paths are given in Figure 12... 

XRD at different temperatures can be used to study phase transitions between different crystallographic forms of a material (e.g., tetragonal vs. monoclinic forms of yttria-stabihzed zirconia). This approach can be used to measure thermal expansion coefficients and to study crystalline-to-amorphous transitions in materials. 

Whilst thermomechanical measurements are routinely used to investigate mechanical stability and measure thermal expansion coefficients, two examples are given which illustrate the use of the technique on the small scale as a micro-analytical tool to identify the distribution of two materials within a matrix and also on a larger scale to investigate the firing of a ceramic material. 

Phase separation has almost no effect on the thermal expansion coefficient of glasses. The measured thermal expansion coefficient is a volume average of the thermal expansion coefficients of the two phases present, in much the same way as the density. 

Other measurements have been made on Ag3RClg compounds. Staffel and Meyer (1988) synthesized the R = Dy-Lu, Y, and Sc compounds and measured thermal expansion. Lerch et al. (1990) characterized AgjYClg structurally and determined its electrical conductivity from room temperature to the melting point conductivity increases sharply at the transition temperature. Below its transition temperature of 350°C, Ag3YClg is isostructural with NajGdClg-I. Steiner and Lutz (1992) examined the related Li3YCl6 and found it to exhibit fast ionic conductivity and complicated order-disorder phase transitions. 

In fig. 24 we show also the lattice constant of SmB obtained by integrating the measured thermal expansion (right-hand scale). By its greater precision, a differential measurement is much more powerful than the direct measurement lattice constant versus temperature. We do not obtain quite the same curve as Tarascon et al. (1980b) or Alekseev et al. (1988), especially the total change of lattice parameter is less than reported, so we calculate between 300 and 4 K only a valence change from 2.6 to 2.58 or about 1%. 

Chatteijee and Comer measured thermal expansion on their 11 at% Sc alloy and found that the a spacing contracted from 300 K down to the Curie temperature (136K) where there was a sharp contraction and a continued contraction in the ferromagnetic state. The c spacing contracted down to the Neel point then expanded upon further cooling. It was observed by Burgardt et al. that scandium diluents in terbium suppress the ferromagnetic state relative to the helical state. 

Bartenev, G. M., Gorbatkina, Yu. A., Luk yanov. I. A. Thermal properties and methods for measuring thermal expansion, q>ecific heat, and thermal conductivity of polymers. Plasticheskie Massy 1963, 56. 

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