Abstracts Book - IMRC 2018

• SC2-P025
THERMAL PROPERTIES OF Co7Sb2O12 SPINEL LIKE SOLID
SOLUTION CERAMIC VARISTOR USING THE FRONT-FACE FLASH
METHOD
Carolina Tabasco Novelo 1 , Nelson Wilbur Pech May 1 , Alejandro Vega Flick 1 , Juan José Alvarado
Gil 1 , Geonel Rodríguez Gattorno 1 , Patricia Quintana Owen 1
1
CINVESTAV-Mérida, Applied Physics, Mexico.
Varistors are electronic ceramics whose resistance is dependent on applied
voltage; they are used for protection of electric and electrical device against
transient and surges voltage. Their characteristic non-linear current-voltage is
defined by the empirical power law:
where J is the current density, B is a constant, E the electric field and α gives the
degree of non-linearity. Since the ceramic varistor is subjected to high voltage
surges, the heat generated in the varistor raise its temperature to such a degree
that the device cannot dissipate the heat, undergoing thermal runaway.
Therefore, knowledge of the thermal properties of a ceramic varistors is
essential to ensure the suitable action and stability. We have found a partial
range of Co7Sb2O12 spinel like solid solution with formula general Li3xCo7-
4xSb2+xO12 in the joint Co7Sb2O12-LiCoSbO4, which have a high degree of nonlinearity
similar to the single-phase system of SnO2-based varistors. In order to
have a full knowledge about the features of this new varistor material and how
dissipate the heat we have measured the thermal diffusivity (D) of the Co7Sb2O12
ceramics doped with lithium sintered 1100 °C to 1250 °C. The measurements
were performed using the front-face flash method, owing to the high accuracy
and fast acquisition time the method provides. The technique consists on
heating the whole front surface of a slab with a short laser pulse (or a step-like
illumination) and record the temperature evolution of the illuminated surface
with an infrared (IR) detector or an IR camera. The thermograms has been
recorded at a frame rate of 500 Hz in the half-windowing mode (320×256 pixels)
with an integration time of 1.6 ms. The thermal diffusivity of the samples was