Tailoring the electrocaloric effect of Pb0.78Ba0.2La0.02ZrO3 relaxor thin film by GaN substrates

The electrocaloric (EC) effect in ferroelectric/antiferroelectric thin films has been widely investigated due to its potential applications in solid state cooling devices. It is demonstrated that the EC effect of the Pb0.78Ba0.2La0.02ZrO3 (PBLZ) relaxor thin films prepared by using a sol–gel method strongly depends on the substrates. The maximum ΔT of PBLZ thin films deposited on Pt(111)/TiOx/SiO2/Si(100) (Pt), LaNiO3/Pt(111)/TiOx/SiO2/Si(100) (LaNiO3/Pt), LaNiO3/n-type GaN (LaNiO3/n-GaN) and LaNiO3/p-type GaN (LaNiO3/p-GaN) substrates is ∼13.08 K, 16.46 K, 18.70 K, and 14.64 K, respectively. Moreover, negative EC effects in a broad temperature range (∼340 K to 440 K) could be obtained in the thin films deposited on LaNiO3/n-GaN and LaNiO3/p-GaN substrates, which is ascribed to higher proportions of orthorhombic antiferroelectric phase to rhombohedral ferroelectric phase induced by the GaN substrates. These results indicate that tailoring the EC effects by changing the substrates could provide a new strategy in designing an EC cooling device with high cooling efficiency.