Multilayer 0.9Pb(Mg 1/3 Nb 2/3 )O 3 –0.1PbTiO 3 elements for electrocaloric cooling

Effect of inactive volume on thermocouple measurements of electrocaloric temperature change in multilayer capacitors of 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3

“…Using the heat capacity and density values that we reported previously [25], the maximum value of |ΔT j | ~ 2.7 K corresponds to an isothermal heat of ~0.19 J, or 918 J kg −1 when normalized by the mass of the active region. The EC properties of our MLCs compare favourably with respect to the EC properties of PMN-PT layers of similar or greater thickness, as found in MLCs [18,19] and bulk samples [4], respectively (table 2). Detailed comparison with these other MLCs is not straightforward due to differences in MLC structure, but our maximum values of |ΔT j | ~ 2.7 K and |ΔE| = 28.8 V µm −1 exceed the values recorded for these other MLCs.…”

“…Current activity in electrocalorics was stimulated by reports of giant EC effects in films of ceramic [10,11] and polymer [12] materials, but a single film cannot generate significant cooling power. However, the technology for fabricating an assembly of ceramic films in the form of an MLC is well established, and EC effects have been demonstrated in commercial [13] and bespoke [5,[14][15][16][17][18][19] MLCs. Such MLCs possess a suitable geometry for EC applications [20], and have been exploited as the working body in the majority of EC prototype coolers [5][6][7][8][9].…”

“…Here we investigate how thermocouple measurements of EC temperature change are influenced by the active/total volume ratio, using MLCs of (1 − x)Pb(Mg 1/3 Nb 2/3 )O 3 -xPbTiO 3 (PMN-PT, x ~ 0.1), which is known to be a good EC material based on studies of thin films [11], bulk samples [21][22][23] and MLCs [17][18][19]. We find that rapidly driven EC effects are highly adiabatic if measured near MLC face centres that lie sufficiently far from the inactive EC material.…”

“…The reader may also note that the correlation between active and inactive volumes permits the possibility of a non-monotonic increase of |ΔT j | with increasing active volume (supplementary figure 3(a)) 4 , and explains the counter-intuitive tendency for |ΔT j | to increase with increasing inactive volume (supplementary figure 3(b)) 4 . If we attempt to follow the approach adopted elsewhere [19] and correct the measured values of |ΔT j | ( figure 3(b)) by assuming that the MLC has thermalized prior to measurement, then we would multiply our measured values by a 'correction' factor α = C total /C active to attempt to obtain adiabatic temperature change |ΔT| for the active region. Assuming that this total/active heat capacity ratio is given by the total/ active volume ratio of our six MLCs (table 1), we find 'corrected' values that exceed the adiabatic limit (|ΔT| ~ 0.9 K for 7.6 V µm −1 starting at 374 K) by a small numerical factor (inset, figure 3(b)).…”

(Na1/2Bi1/2)TiO3‐based lead‐free co‐fired multilayer actuators with large strain and high fatigue resistance

“…Both of the samples exhibit strong frequency dispersion below the first anomaly indicating the relaxor nature of NBT–BT–3AN . The first anomaly is shifted from 106°C in the bulk to 178°C in the MLA1; however, a similar effect was also reported for 0.9Pb(Mg 1/3 Nb 2/3 )O 3 –0.1PbTiO 3 MLAs . The reason for the difference between the bulk and multilayer actuators is unknown.…”