Alternative Caloric Energy Conversions - Magnetocaloric Energy Conversion: From Theory to Applications - page 398

Table 10.2 Electrocaloric properties of thick- lm ceramics
Material

a
(K) Δ

E (MVm − 1 ) q r,max
(Jkg − 1 )

Δ T ad

(K)

Δ s is

(Jkg − 1 K − 1 )

T ref Measurement

procedure

Note References

MC b BaTiO 3 7.1 50 333 80 16,473 Direct [ 24 ]

MC b BaTiO 3 0.55 / 350 30 / Direct [ 25 ]

MC b PST 2.4 / / 13.8 / Direct [ 28 ]

PLZT
8/65/35

1.8 1.5 384 6.8 575 Direct / [ 29 ]

a T ref

— temperature at which Δ T ad , Δ s is and q r,max were obtained

b MC

— multilayer capacitor

lm ceramics have attracted a lot of attention due to the discovery of the
so-called giant electrocaloric effect in PZT thin-

Thin-

lm ceramics [ 8 ]. The thickness of
these materials can be as little as a few 100 nm and hence direct measurements are a
great challenge. Therefore, the evaluation of the electrocaloric effect in thin-

lm
materials is usually reported on the basis of indirect measurements. For example, in
2013 Peng et al. [ 30 ] predicted an electrocaloric effect of 45.3 K in thin- lm

Pb 0.8 Ba 0.2 ZrO 3 (PBZ) ceramics obtained by an indirect measurement. Nevertheless,
Lu et al. [ 31 ] reported on a directly measured electrocaloric effect of 40 K in
400-nm-thick La-doped Pb(ZrTi)O 3 (PLZT) relaxor ceramics. Some other thin-

lm
ceramic materials, together with their electrocaloric properties, are presented in
Table 10.3 . In comparison with bulk and thick- lm ceramics, the electrocaloric

effect in thin- lm ceramics can be one order larger. The main reason for this lies in

the higher dielectric strength of thin-

lm materials, which can be as high as

120 MVm − 1 [ 31 ].
In conclusion, it can be said that all three groups of ceramics have the potential
for future cooling or other energy conversion applications. Though bulk ceramics
do not exhibit suf cient adiabatic temperature changes to be used in a single-stage

cooling device, they could be applied in devices where heat regeneration allows a
signi

lm
ceramics, which are usually in the form of a multilayer capacitor. However, they

cant increase of the temperature span [ 37 ]. This also holds true for thick-

Table 10.3 Electrocaloric properties of thin-lm ceramics
Material

a
(K)

Δ E (MVm − 1 ) q r,max
(Jkg − 1 )

Δ T ad
(K)

Δ s is
(Jkg − 1 K − 1 )

T ref Measurement

procedure

References

PLZT 8/65/35 40 50 318 120 14,900 Direct [ 31 ]

PBZ 45.3 / 290 59.8 / Indirect [ 30 ]

PMN-0.35PT 31 / 413 74.7 / Indirect [ 32 ]

PMN-0.1PT 5 / 348 89.5 / Indirect [ 33 ]

PMN-0.07PT 9 / 298 72.3 / Indirect [ 34 ]

PST − 6.2 − 6.3 341 77.4 2,129 Indirect [ 35 ]

PZ 11.4 / 508 40 / Indirect [ 36 ]

PZT 12 / 499 48 / Indirect [ 8 ]

a T ref — temperature, at which Δ T ad , Δ s is and q r,max were obtained