GoKawiilSamples
The active area of MLC1 of 85PST–15PMW was used for STEM. MLC1 of 85PST–15PMW and MLC1 of 90PST–10PMW were used for indirect EC measurements from which efficiency was evaluated and for direct measurements of EC temperature change that were converted to effective temperature change. MLC2 of 85PST–15PMW and MLC2 of 90PST–10PMW were crushed to form powders for XRD. MLC2 of 85PST–15PMW and MLC2 of 90PST–10PMW were used for zero-field calorimetry and direct measurements of EC heat. MLC3 of 85PST–15PMW and MLC3 of 90PST–10PMW were used for optical images. MLC4 of 85PST–15PMW and MLC4 of 90PST–10PMW were used for dielectric spectroscopy. MLC5 of 85PST–15PMW was tested for fatigue. MLC6 of 85PST–15PMW was used to measure leakage current.
MLC fabrication
Powders of high-purity Pb 3 O 4 , Ta 2 O 5 and MgWO 4 (Kojundo Chemical Laboratory Co., Ltd) and Sc 2 O 3 (Shin-Etsu Chemical Co., Ltd) were weighed, ball-milled for 16 h in distilled water with balls of partially stabilized zirconia, dried and then pulverized. The powder mixture was then calcinated at 850 °C for 4 h in air. Subsequent ball-milling that used partially stabilized zirconia balls with an organic solvent and binder resulted in a slurry for casting green sheets using the doctor blade technique. These green sheets were sliced, electroded by screen-printing Pt paste, stacked, pressed and cut to obtain green MLCs. After burning off the binder at 500 °C for 24 h, the proto-MLCs were sintered at 1,250 °C for 4 h in a Pb-containing atmosphere. Terminals were formed by painting on a bespoke Ag paste and firing in air at 750 °C for 10 min.
MLC geometry
MLCs of 85PST–15PMW had external dimensions of 10.10 × 7.18 × 0.78 mm3, an active volume of 32.6 mm3 that comprised 19 layers of thickness 35 μm and area 49 mm2, Pt inner electrodes of thickness 2 μm and an active volume fraction of v active = 58%. MLCs of 90PST–10PMW had external dimensions of 10.20 × 7.28 × 0.78 mm3, an active volume of 32.8 mm3 that comprised 19 layers of thickness 36 μm and area 48 mm2, Pt inner electrodes of thickness 2 μm and v active = 57%.
Thermalization of active and inactive layers
Within the active area and away from the periphery, we identify |ΔT j | = f 1 |ΔT| = 0.85|ΔT| for both PST–PMW compositions by assuming complete thermalization between the 19 active PST–PMW layers (that would develop adiabatic temperature change |ΔT| if isolated) and the inactive layers that comprise two outer layers of PST–PMW and 20 inner Pt electrodes. The calculation assumes an off-peak volumetric heat capacity of c ≈ 2.5 MJ K−1 m−3 for PST–PMW at 273 K (Supplementary Note 4) and c ≈ 2.8 MJ K−1 m−3 for Pt.
XRD
We used a Bruker D8 Advance diffractometer with Cu-Kα radiation and a LYNXEYE EX detector that obviates the need for a monochromator. For MLCs crushed to a powder, we obtained 2θ–ω step scans with a 2θ step of 0.01°, a scan speed of 1.5 s step−1 and a fixed illuminated length that increases the effective scattering volume at higher values of 2θ. The diffraction profiles we present and analyse were corrected with DIFFRAC.EVA software to make the effective scattering volume constant. Lattice parameters of a c ≈ 8.13 Å (85PST–15PMW) and a c ≈ 8.14 Å (90PST–10PMW) were estimated from the positions of the 422 reflections generated by Cu-Kα1 radiation (Supplementary Note 2). The intensities of the unsplit 111 and 200 reflections, determined by fitting pseudo-Voigt functions, were used to calculate the B-site order between high-valence and low-valence cations (S 111 ≈ 0.99 for 85PST–15PMW, S 111 ≈ 0.97 for 90PST–10PMW) (Supplementary Note 2).
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