1：Experimental Design and Method Selection:

The study uses sol-gel processing for thin film deposition, chosen for its low cost, scalability, and compositional control. X-ray diffraction (XRD) is employed for structural analysis, and impedance spectroscopy and ferroelectric analyzers for electrical characterization.

2：Sample Selection and Data Sources:

Thin films of SrTiO3 (ST) and K

3：5Na5NbO3 (KNN) are deposited on various substrates:

Al2O3/Pt, MgO/Pt for ST, and Si/SiO2/TiO2/Pt, SrTiO3/Pt for KNN. Substrates are selected based on thermal expansion coefficients to induce different stress states.

4：List of Experimental Equipment and Materials:

Equipment includes spin-coater (Chemat Technology KW-4A), XRD diffractometer (Philips X'Pert MPD and MRD), SEM (Hitachi SU-70 and S4100), SFM (Multimode Digital Instrument Nanoscope IIIa), LCR-meter (Agilent E4980A and HP 4284A), ferroelectric analyzer (aixACCT TF Analyzer 1000 and 2000), RTA system (Qualiflow Jipelec JetFirst 200), and cryogenic system (Displex ADP-Cryostat HC-2). Materials include strontium acetate, tetra-n-butyl orthotitanate, acetic acid, 1,2-propanediol, ethanol, potassium acetate, sodium acetate, niobium pentaethoxide, 2-methoxyethanol, and various substrates.

5：2). Materials include strontium acetate, tetra-n-butyl orthotitanate, acetic acid, 1,2-propanediol, ethanol, potassium acetate, sodium acetate, niobium pentaethoxide, 2-methoxyethanol, and various substrates. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: For ST films, precursor solution is prepared and spin-coated on substrates at 4000 rpm for 30s, with pyrolysis at 300°C for 1 min per layer, followed by furnace annealing at 900°C for 60 min. For KNN films, solution with 5% potassium excess is spin-coated at 3000 rpm for 30s, pyrolyzed at 350°C for 2 min per layer, and annealed via RTA at 750°C for 5 min. Characterization involves XRD for phase and strain analysis, SEM/SFM for morphology, and electrical measurements using sputtered Au top electrodes.

6：Data Analysis Methods:

Strain is calculated using XRD sin2ψ method, stress is derived from Young's modulus and Poisson's ratio, thermal stress is computed based on TEC differences, and electrical properties are analyzed from hysteresis loops and permittivity measurements.