Major physical characteristics of Rochelle salt: the role of thermal strains

Abstract

We compare the results for the related to the shear strain ε 4 physical characteristics of Rochelle salt obtained within the recently developed modified two-sublattice Mitsui model that takes into account the strain ε 4 and the diagonal components of the strain tensor ε 1 , ε 2 , ε 3 with the results of the previous modification of the Mitsui model with the strain ε 4 only. Within the framework of the model with the diagonal (thermal expansion) strains, we also reexamine the effects of the longitudinal electric field E 1 on the dielectric properties of Rochelle salt.

Piezoelectric resonance in Rochelle salt: The contribution of diagonal strains

“…Their frequency variation is perceptible only in the region of the microwave dispersion of the dielectric susceptibility. However, in the piezoelectric resonance region, which is expected to be in the 10 4 −10 7 Hz range, depending on temperature and sample dimensions, well separated from the region of the microwave relaxation,c E i j (ω) and e i j (ω) (13) are very close to the corresponding static quantities (see [16,19]) and coincide with them at ω → 0.…”

“…It is easy to verify that the boundary conditions (19) are satisfied. Substituting (28) into the two first equations of (27) and noting that we can write that…”

“…Let us analyze the above results. In the static limit (ω → 0, R 4 (ω) → 1) from (26) we obtain the static permittivity of a free crystal (see [19]); in the high frequency limit ( ∞ k,l=0 64/[(2k + 1) 2 (2l + 1) 2 π 4 ] = 1, and R 4 (ω) → 0) we get a dynamic permittivity (10) of a mechanically clamped crystal, exhibiting relaxational dispersion in the microwave region. Thus, eq.…”

Defect-mediated relaxation and non-linear susceptibilities of Rochelle salt

“…Here α is the parameter setting the time scale of this dynamics; its value is usually found by fitting theoretical curves of the permittivity in the microwave frequency range to experiment [3,4,26]. For dynamics of the defect pseudospins a similar equation is obtained…”

“…(11). The values of the parameters of the modified Mitsui model J 0 , K 0 , ∆ 0 , ψ ± 3i , ψ 4 , c E0 i j and others were chosen in [6,26] by fitting the theoretical pressure dependences of the transition temperatures, as well as the temperature dependences of several dielectric, piezoelectric, and elastic characteristics to experimental data. In particular, the major criterion of the fitting was to get T C2 = 297 K and T C1 = 255 K at ambient pressure.…”