1：Experimental Design and Method Selection:

The study uses composition engineering to tune phase transitions and induce diffuse phase transitions in (1-x)NaNbO3-xBaTiO3 ceramics. The methodology includes conventional solid-state reaction for synthesis, characterization of phase and morphology, dielectric and polarization measurements, and direct electrocaloric measurements.

2：Sample Selection and Data Sources:

Ceramic samples with compositions x=0.20, 0.22, 0.24, and 0.27 were prepared. Data sources include XRD for phase analysis, SEM for morphology, dielectric permittivity and loss measurements, P-E hysteresis loops, specific heat capacity from DSC, and direct electrocaloric temperature change measurements.

3：20, 22, 24, and 27 were prepared. Data sources include XRD for phase analysis, SEM for morphology, dielectric permittivity and loss measurements, P-E hysteresis loops, specific heat capacity from DSC, and direct electrocaloric temperature change measurements. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment includes planetary mill (QM-3SP4), X-ray diffractometer (Philips X-Pert ProDiffractometer), scanning electron microscope (SU-1510), LCR meter (E4980A), ferroelectric test system (TF Analyzer 2000), differential scanning calorimeter (TA Q2000), and a home-built setup for direct electrocaloric measurements. Materials include Na2CO3, BaCO3, Nb2O5, TiO2 powders, PVA binder, zirconia balls, alcohol, and silver electrodes.

4：Experimental Procedures and Operational Workflow:

Powders were mixed, calcined, pressed into cylinders, sintered, polished, and electrodes applied. Measurements included XRD, SEM, dielectric properties, P-E loops, specific heat, and direct ΔT measurements at various temperatures and electric fields.

5：Data Analysis Methods:

Data analysis involved comparing dielectric permittivity and loss, extracting polarization from P-E loops, using the Maxwell relation for indirect ΔT calculation, and direct measurement of temperature changes.