- The paper demonstrates that reducing ceramic thickness significantly improves energy storage and electrocaloric properties in lead-free BCZT ceramics.
- It employs sol-gel synthesis alongside XRD and SEM analyses to achieve a dense perovskite structure with coexisting tetragonal and orthorhombic phases.
- Performance metrics include a recoverable energy density of 0.24 J/cm³ and an electrocaloric responsivity of 0.42 K mm/kV, supporting the LGD theoretical model.
Introduction
The paper "Improved energy storage and electrocaloric properties of lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramic" investigates a lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramic synthesized via the sol-gel method to enhance its energy storage and electrocaloric properties. The focus is on reducing ceramic thickness to improve these properties. This study thoroughly evaluates the dielectric, ferroelectric, energy storage, and electrocaloric characteristics of the synthesized BCZT, supported by both experimental and theoretical approaches.
Synthesis and Structural Properties
The BCZT ceramics were synthesized using a sol-gel method with stoichiometric precursors, yielding a powder calcined at 1000 °C and sintered at 1420 °C. XRD analysis revealed a single-phase perovskite structure with a coexistence of tetragonal and orthorhombic phases, indicating the presence of a morphotropic phase boundary (MPB). SEM analysis confirmed a dense microstructure with an average grain size of 45 μm and a high relative density of approximately 95%.
Dielectric and Ferroelectric Properties
The dielectric study demonstrated two phase transitions: orthorhombic to tetragonal around 300 K and tetragonal to cubic around 352 K. The maximum dielectric constant achieved was 7841, with low dielectric loss, attributed to the dense microstructure. The ferroelectric properties were appraised through P-E hysteresis loops, showing characteristic transitions from ferroelectric to paraelectric phases with increasing temperature. Notably, a lower coercive field was observed due to the large grain size, which facilitates domain switching.
Energy storage properties were derived from P-E loops, with the BCZT ceramic exhibiting a recoverable energy density (Wrec) of 0.24 J/cm³ and a total energy density (Wtotal) of 0.27 J/cm³ at 55 kV/cm. The energy storage efficiency reached approximately 88% at 423 K. The results are competitive compared to previous studies, indicating that synthesis and grain size significantly influence energy storage capabilities.
Electrocaloric Effect and Modeling
The electrocaloric effect (ECE) was assessed indirectly through Maxwell's relations, yielding a maximum temperature change (ΔT) of 2.32 K and an electrocaloric responsivity of 0.42 K mm/kV. The refrigeration capacity (RC) and coefficient of performance (COP) were calculated as 4.59 J/kg and 12.38, respectively. These values underscore the potential of BCZT ceramics for eco-friendly applications. Furthermore, the Landau-Ginzburg-Devonshire (LGD) theory was employed to compare theoretical predictions with experimental results, confirming consistent trends and reinforcing the theoretical model's validity.
Conclusion
The study presents a comprehensive analysis of BCZT ceramics fabricated using the sol-gel method. The reduction in ceramic thickness significantly enhances energy storage and electrocaloric properties, making BCZT a promising material for dielectric energy storage and electrocaloric applications. The coherence between experimental and theoretical results, as established by the LGD theory, fortifies the understanding of these complex phenomena. This work contributes to the advancement of lead-free materials for sustainable energy applications.