Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10640055 | Materials Science and Engineering: B | 2005 | 7 Pages |
Abstract
The elastic properties of single crystals of the ferroelectric family Li2 â xNaxGe4O9 with x = 1, 0.8, 0.6 and 0.4 were studied in the range between 100 and 360 K by ultrasonic resonance techniques. At room temperature a distinct anomalous reduction of all elastic constants cij occurs with increasing lithium content in an amount of up to 26% (c44). At 293 K the thermoelastic constants Tij = d(log cij)/dT and the piezoelastic constants Pij = dcij/dp (T, temperature; p, hydrostatic pressure) vary only slightly with composition, except T44 and P44, which in the case of x = 0.4 possess anomalous positive and negative signs, respectively. Approaching the transition temperature T0, which depends strongly on the composition, a softening of the constants c44, c55, c33 and c23 in an amount of about 5% is observed. Below T0 these constants increase with lower temperatures. In contrast, the constants c11, c22, c12 and c66 are much less affected by the transition process. Further, a strong anomalous negative thermal expansion appears along [0 0 1] below T0. These phenomena show that the transition process is related to bonding interactions along [0 0 1]. A comparison of the elastic properties of the Li2 â xNaxGe4O9 family with Li2Ge7O15 reveals unexpected large differences, particularly near the transition temperature.
Related Topics
Physical Sciences and Engineering
Materials Science
Electronic, Optical and Magnetic Materials
Authors
S. Haussühl, E. Haussühl, M.D. Volnyanskii,