Alternative Caloric Energy Conversions - Magnetocaloric Energy Conversion: From Theory to Applications - page 416

Fig. 10.16 Schematic presentation of a pyroelectric material in an electrical circuit, a The
pyroelectric material is in a thermal equilibrium, b The pyroelectric material is heating up, c The
pyroelectric material is cooling down

(Fig. 10.16 c). To describe how the polarization of a pyroelectric material changes
with temperature, a so-called pyroelectric coef cient is used and is de ned as [ 1 ]:

d

dT

p ¼ ð 10 : 13 Þ

where T is the temperature of the pyroelectric material. If the expression for the
surface charge density is inserted into Eq. ( 10.13 ), the pyroelectric coef

cient can

be written as:

d ðe 0 E þ P Þ

p ¼ ð 10 : 14 Þ

dT

eld-induced
polarization is much smaller than the spontaneous polarization, the pyroelectric
coef

For a constant electric eld and with the assumption that the

cient can be expressed as [ 1 ]:

o P s

o

p ¼ ð 10 : 15 Þ

T

E ; X