I. Abstract of the Paper’s Core Research

• Photon sintering enables differentiated heating, with the coating at high temperature and the substrate at low temperature.

Millisecond‑scale broadband flash pulses heat only the PZT ceramic film, raising its surface temperature instantaneously above 900°C to achieve grain fusion; the stainless steel substrate reaches a maximum of 170.7°C, while the PET flexible substrate exhibits no melting or deformation, thereby completely avoiding the high‑temperature damage—exceeding 1,000°C—that would otherwise degrade plastic substrates.

• The piezoelectric performance of PZT sintered at low temperatures is superior to that of traditionally high-temperature-sintered PZT.

The residual polarization of the stainless-steel‑substrate photonic sintered sample is Pr = 32.4 μC/cm², significantly exceeding that of the 1000°C furnace‑sintered sample (17.1 μC). The piezoelectric voltage coefficient g₃₃ = −17.9 × 10⁻³ V·m/N, which is higher than that of conventionally sintered samples, while exhibiting lower leakage current and a more favorable ferroelectric hysteresis loop.

• Flexible PET substrates can be directly used to fabricate functional PZT devices.

Aluminum electrode on a PET substrate fabricated via direct aerosol printing followed by photonic sintering, with Pr = 23.1 μC/cm² and g₃₃ = −17.3 × 10⁻³; the flexible substrate retains excellent piezoelectric response without requiring a thin-film transfer process.

• Aerosol Direct Writing of Precisely Controllable Thick-Film Structures

Maskless digital fabrication with a controllable line width of 20–100 μm and a film thickness of 6–10 μm; the ink is homogenized to disperse particles, achieving a ceramic particle size distribution where 70% of particles are smaller than 1.5 μm, resulting in printed films that are uniform and free of agglomerates and pores.

• Sintering by-products are significantly suppressed, reducing perovskite phase impurities.

Flash short‑time thermal treatment significantly reduces PbO volatilization at high temperatures, and the defect‑related phase in pyrochlore‑structured films exhibits markedly lower intensity than that in furnace‑annealed films, thereby fundamentally mitigating the degradation of piezoelectric performance.

II. Complete PZT Piezoelectric Film Process for Aerosol Spraying and Its Core Advantages

(1) Complete Aerosol + Photonic Sintering Preparation Process

• A water-based ceramic ink formulated with PZT powder, deionized water, ethylene glycol, a dispersant, and a binder; the particles are rapidly homogenized and dispersed.
• Plasma cleaning for degreasing of stainless steel, PET substrates, and more;
• Optomec aerosol ultrasonic atomization, using a 200 μm nozzle and a printing speed of 10 mm/s, was employed to repeatedly deposit two layers of thick PZT films.
• Drying in a 200°C vacuum oven for 2 h completely removes the solvent.
• Two groups were compared: (1) argon atmosphere, held at 1000°C in a tube furnace for 1 hour; (2) pulsed xenon lamp sintering (250 V, 1300 μs pulse duration, 15 flashes).
• A copper electrode was deposited by evaporation, and the ferroelectric and piezoelectric parameters were measured after polarization at 150°C under an electric field of 20 kV/cm for 2 hours.

(II) Five Core Advantages of Aerosol-Based Processes (Comparison with Screen Printing, Spin Coating, and Inkjet)

• Maskless High-Precision Direct Patterning of Piezoelectric Materials

The minimum feature linewidth is 20 μm, enabling flexible design of arrays, cantilevers, and circular piezoelectric elements; screen printing achieves a minimum linewidth of 100 μm but suffers from poor pattern resolution, while spin coating cannot enable region‑specific patterning.

• The thickness of the thick film is precisely controllable, making it suitable for various piezoelectric output requirements.

Repetitive printing allows for free adjustment of the number of passes, enabling film thicknesses of 6–10 μm, whereas spin coating can only produce ultrathin films, making it difficult to obtain thick films with high charge output.

• Non-contact printing compatible with both rigid metal and flexible plastic substrates.

A safe spray distance of 3–5 mm ensures that the lightweight, flexible PET film is not subjected to mechanical compression or wrinkling; in contrast, screen-printing pressure can easily damage flexible substrates.

• Universal compatibility with ceramic inks; controllable powder dispersibility.

Equipped with a dedicated dispersion system, it ensures long‑term atomization without nozzle clogging; large‑size ceramic particles are effectively dispersed, resulting in a dense thin film free of macroscopic porosity defects.

• Small-batch rapid iteration, no need for custom photolithography masks.

With CAD, you can instantly adjust the dimensions and layout of piezoelectric components, enabling the production of multiple process‑comparison samples in a single day and significantly shortening the R&D cycle for piezoelectric materials.

III. Five Core Technological Innovations of This Study

Innovation 1: A novel low-temperature piezoelectric manufacturing process combining aerosol printing with transient photonic sintering.

Innovation 2: A selective localized heating mechanism that achieves a substantial temperature difference between the film and the substrate.

Innovation 3: Photon sintering reduces lead volatilization and suppresses pyrochlore‑type impurity phases.

Innovative Four-Step Standardized Process for Dual-Substrate High- and Low-Temperature Applications

Innovation: 5 High-Residual-Polarization Flexible Piezoelectric Films Achieved

IV. Existing Process Challenges and Corresponding Solutions for Overcoming Them

Challenge 1: PZT ceramics require high-temperature crystallization above 1000°C, whereas flexible plastics have melting points below 300°C and cannot withstand such temperatures.

Challenge 2: Conventional long‑duration high‑temperature sintering leads to Pb volatilization, resulting in the formation of pyrochlore impurities and a decline in piezoelectric performance.

Challenge 3: Screen printing and spin coating cannot be miniaturized to fabricate custom piezoelectric arrays, resulting in rough surface patterns.

Challenge 4: Conventional flexible piezoelectric fabrication requires high-temperature substrate sintering followed by lift-off and transfer, resulting in numerous process steps and low yield.

Challenge 5: Ceramic inks are prone to agglomeration, resulting in printed films with numerous pores and severe leakage.

V. Future Diversified Industrial Application Scenarios

• Flexible Wearable Vibration Energy-Harvesting Film

• Miniature MEMS ultrasonic and pressure sensor arrays

• Soft robotic tactile sensing film

• Industrial Nondestructive Testing Ultrasonic Probe

• High-Performance Piezoelectric Ceramic Rapid Development Platform for Universities

Figure 1. X-ray diffraction patterns of commercially available PZT powders reveal peaks characteristic of a highly crystalline perovskite structure.

Table I. Composition of Lead Zirconate Titanate Ink

Figure 2. After stirring with a homogenizer, the PZT powder undergoes deagglomeration, forming discrete particles (a). The inset in (a) is one of five schematic illustrations used to determine the particle size distribution of the powder. The particle size distribution of the PZT particles after homogenization is shown in (b): more than 70% of the particles have diameters less than 1.5 μm, and the largest measured particle diameter is 3.54 μm.

Figure 3. The light‑intensity spectrum (black) generated by the Novacentrix lamp under a 250 V pulse configuration, with its peak emission in the violet region. The absorption spectrum of the dried PZT thin film (blue) exhibits substantial overlap with the lamp’s emission spectrum: absorbance is highest in the ultraviolet region (<400 nm); however, due to the relatively large film thickness (>30 μm), significant absorption is observed across the entire wavelength range.

Figure 4. Schematic diagram of the RC bridge circuit used for measuring the capacitance of a PZT thin film. By adjusting the resistance value of R2, the bridge can be balanced. The capacitance (Cx) of the PZT device is equal to the ratio of R1/C1 to R2.

Figure 5. Schematic diagram (a) and structural schematic (b) of the homemade cylindrical system used for measuring the piezoelectric voltage coefficient (g33).

Figure 6. Device model used for COMSOL heat-transfer simulations (enlarged schematic). Points A, B, and C represent three study locations, corresponding to the temperature variations at the PZT layer during photonic sintering, at the interface between PZT and stainless steel, and along the thermocouple’s position, respectively.

Table II. Material Properties Used in the Finite Element Simulation

Figure 7. (a) Simulated temperature‑time profiles at points A, B, and C during all 15 flash events. (b) Detailed data for the region enclosed by the dashed box in (a), showing the temperature evolution at points B and C at the end of the final pulse of the exposure current. The maximum temperature on the PZT surface reached 917.4°C (A), whereas the temperature at the PZT–SS interface rose only to 192.7°C (B). At the thermocouple measurement point (C), the substrate attained a peak temperature of 177.7°C, indicating that the actual interfacial temperature is approximately 4% lower than the simulated value.

Figure 8. SEM images of the PZT thin film before sintering (a), after thermal sintering (b), and after photonic sintering (c). The dried film exhibits a uniform microstructure with high PZT particle density; compared with the thermally sintered film, the photonic-sintered film shows a more extensive region of melt‑induced grain boundaries and particle agglomeration on its surface.

Figure 9. EDS (energy-dispersive X-ray spectroscopy) analysis results for unsintered and sintered PZT thin films. The unsintered PZT film (black) exhibits a strong carbon peak at 265; the photonic sintering method (green) reduces the carbon peak to 14, comparable to the result obtained with conventional thermal sintering (red), which is 12. The lower carbon content indicates that organic residues were removed from the PZT thin film during the sintering process.

Figure 10. EDS distributions of carbon content across the entire thickness of the films prepared by thermal sintering (a) and photonic sintering (b). Carbon levels remain low throughout the film thickness (average values of 12.5 for the thermally sintered sample and 12.8 for the photonic‑sintered sample), indicating that organic residues have been substantially removed from the films. Prior to sintering, the carbon content exceeded 265. Cross‑sectional micrographs of the thermally sintered film (c) reveal larger grain sizes compared to those of the photonic‑sintered film (d), particularly in the region near the substrate.

Figure 11. XRD patterns of PZT thin films prepared by thermal sintering (a) and photonic sintering (b). Both types of PZT thin films exhibit the pyrochlore phase (labeled “Py”), which arises from lead loss during high-temperature sintering; however, in the photonic-sintered film, the intensity of this phase is markedly reduced.

Table III. Electrical Properties of PZT Thin Films Prepared by Different Sintering Methods

Figure 12. Low-frequency hysteresis loops show that the remanent polarization of the optically sintered (green) PZT film (32.4 μC/cm²) is higher than that of the thermally sintered (red) film (17.1 μC/cm²). Both films exhibit superior ferroelectric properties compared to the unsintered (black) film (0.03 μC/cm²). The electric field strength applied during the ferroelectric measurements was 20 kV/cm, with a frequency of 10 Hz.

Figure 13. (a) SEM image showing that the sintered particles have fully fused onto the SS substrate. (b) EDS spectrum of the PZT thin film on the PET substrate, obtained via photonic sintering; the spectrum indicates a low carbon content of approximately 15%. The curve in the upper right corner depicts the hysteresis loop of the PZT thin film at the aluminum electrode on the PET substrate, with a remanent polarization of 23.1 μC/cm² and a coercive field of 5.1 kV/cm. Ferroelectric measurements reveal that its performance surpasses that of thermally sintered PZT.