where A is a constant related to th

where A is a constant related to the device dimensions and resistivity (ρ). ‘q’ is the activation energy for the hopping process and ‘k’ is Boltzmann's constant. B-value is simply ‘q/k’ and is usually calculated using
equation(2)
B298/358=(T298T358ln(R298/R358))/(T358−T298)
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where R298 and R358 are the resistance values at 298 K (T298) and 358 K (T358), respectively. The temperature coefficient of resistance (α) is defined as the rate of change of resistance (R) with temperature (T) to the resistance at a specified temperature and is given by
equation(3)
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Fig. 3 shows a linear dependence of logarithm of resistivity with reciprocal of absolute temperature over a wide temperature range for the aged disc thermistors, which is an indication of excellent NTC thermistor characteristics.

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Fig. 3.
Relationship between log resistivity and 1/T for disc thermistors.
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