Nearly constant loss

A. Nearly Constant Loss and Low-Temperature Properties of Molecular Glasses... 

Figure 52. Double logarithmic plot of the dielectric loss data (tan 8) of several type A glass formers as a function of temperature. Below 3 K the tunneling regime with the tunneling plateau is recognized the temperature range 3 < T < 30 K corresponds to thermally activated dynamics in double-well potentials at higher temperatures, nearly constant loss is found in the corresponding spectra. (Adapted from Ref. 50.)...

The broad width of the JG relaxation can be accounted for by the broad transition from the cage dynamics (revealed by the nearly constant losses) to the fully cooperative Kohlrausch relaxation [36]. In fact, it is important to recall that the time scale where JG relaxation takes place usually exceeds tc, especially in molecular glass-formers, whereas the onset of many-molecule dynamics starts at tr 2 ps. So, when tc short time and then a gradual development of cooperativity occurs when increasing numbers of molecules are ready to reorient independently. In the region tc [Pg.550]

Nearly Constant Loss Models. Nearly constant loss (NCL) is evidenced by a power-law dependence of <7 ( ) on frequency with an exponent very close to unity, leading to e (< ) loss response that varies only slightly over a snbstantial frequency... 

Although a PCPE may be used to model NCL data with equal slopes for both a (0) and " (0) since they both involve the same jpc 1 exponent, some data may be better represented by such power-law response for cr ((u) but by a function that yields a very close approximation to constant loss for the el (o) part of the response (Nowick et al. [1998]). In the absence of hopping, just the series combination of an ideal capacitor and a CPE can yield such behavior with very nearly constant loss over several decades of frequency (Macdonald [2001a]). 

K1 The Kohlrausch frequency response model derived from the KO model see Section 4.2, Eq. (1) with Cz = ci , Eq. (3), and Eq. (4). Some composite models are the CKO, CKl, PKl, CKOS, CKIS, EMKl, CKIEL, CPKl. Parallel elements appear on the left side of KO or Kl, and series ones on the right. C denotes a parallel capacitance or dielectric constant. NCL Nearly constant loss e"((0) nearly independent of frequency over a finite range... 

K. L. Ngai and C. Leon [2002] Cage Decay, Near Constant Loss, and Crossover to Cooperative Ion Motion in Ionic Conductors Insight from Experimental Data, Phys. Rev. B 66, 064308. 

A. Rivera, C. Leon, J. Sanz, J. Santamaria, C. T. Moynihan, and K. L. Ngai [2002] Crossover of Near-Constant Loss to Ion Hopping Relaxation in lonically Conducting Materials Experimental Evidences and Theoretical Interpretation, J. Non-Cryst. Solids 305, 88-95. 

B. Roling, C. Martiny, and S. Murugavel [2001] Ionic Conduction in Glass New Information on the Interrelation Between the Jonscher Behavior and the Nearly Constant-Loss Behavior from Broadband Conductivity Spectra, Phys. Rev. Lett. 87, 085901-1-085901-4. 

A correlated localized motion, which creates the Nearly Constant Loss effect... 

Dynamics of Mobile Ions in Materials with Disordered Structures - the Case of Silver Iodide and the Two Universalities, Fig. 3 Second universality (Nearly Constant Loss) low-temperature conductivity isotherms displaying a linear frequency dependence and essentially no temperature dependence (Data from 0.3 Na20 0.7 B2O3 glass [11])... 

In 1991, A.S. Nowick and his coworkers discovered a new, second universality, which is ubiquitous in disordered ionic materials ( present in every plastic bag ) but becomes visible only at sufficiently low temperatures and/or high frequencies [30]. The phenomenon is also called Nearly Constant Loss (NCL) effect, since the dielectric loss function, e" oc ajv, appears to be virtually independent of both frequency and temperature, cf. Fig. 3. 

Laughman DM, Banhatti RD, Funke K (2010) New nearly constant loss feature detected in glass at low temperature. Phys Chem Chem Phys 12 14102... 

Banhatti RD, Laughman D, Badr L, Funke K (2011) Nearly constant loss effect in sodium borate and silver meta-borate glasses new insights. Solid State Ion 192 70... 

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