High coupling KNbO3 width-extensional vibrators with a polar multidomain structure
The longitudinal piezoelectric coupling factor for the width-extensional mode of a thin KNbO3 plate, k11[prime]" align="middle"/>, has theoretically been predicted to be as high as 82.4% for the 43.5&...
The longitudinal piezoelectric coupling factor for the width-extensional mode of a thin KNbO3 plate, k11[prime]" align="middle"/>, has theoretically been predicted to be as high as 82.4% for the 43.5&...
Elimination of defect-induced color instabilities in polymer light-emitting devices
We demonstrate that utilizing a blue light-emitting oligo(ethylene oxide)-grafted conjugated poly(p-phenylene) (PPP-OR11) as an active layer in a light-emitting electrochemical cell (LEC) preserves a ...
We demonstrate that utilizing a blue light-emitting oligo(ethylene oxide)-grafted conjugated poly(p-phenylene) (PPP-OR11) as an active layer in a light-emitting electrochemical cell (LEC) preserves a ...
Limitations of the stretched exponential function for describing dynamics in disordered solid materials
J. Appl. Phys. 97, 063507 (2005); doi:10.1063/1.1852069
Published 4 March 2005
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Around the glass transition temperature, relaxation dynamics in glass-forming materials follows a strong nonexponential behavior. It is widely accepted that an empirically based stretched exponential function, known as the Kohlrausch–Williams–Watts (KWW) function, 
(t)=e–(t/
)
, describes universally a broad variety of experimental data. Using intuitive pictures and ellipsometric measurements, we show that (1) in order to describe the dynamics in disordered materials such as in polymers using a KWW function, the response has to be considered over a specific region of time, (2) a single KWW function is not sufficient for correctly describing more than one relaxation processes, and (3) in certain cases, stretching exponents depending on temperature do not cover the ranges previously suggested (from 0 to 1, e.g., as a sigmoid function). As an example, we show that the temperature dependence of the stretching exponent 
(T) depends highly on how the curve fits with the KWW function are performed.
©2005 American Institute of Physics
(t)=e–(t/), describes universally a broad variety of experimental data. Using intuitive pictures and ellipsometric measurements, we show that (1) in order to describe the dynamics in disordered materials such as in polymers using a KWW function, the response has to be considered over a specific region of time, (2) a single KWW function is not sufficient for correctly describing more than one relaxation processes, and (3) in certain cases, stretching exponents depending on temperature do not cover the ranges previously suggested (from 0 to 1, e.g., as a sigmoid function). As an example, we show that the temperature dependence of the stretching exponent (T) depends highly on how the curve fits with the KWW function are performed.
©2005 American Institute of Physics
| History: | Received 20 September 2004; accepted 29 November 2004; published 4 March 2005 |
| Permalink: |
http://link.aip.org/link/?JAPIAU/97/063507/1 |
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REFERENCES (16)
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