Hu et al. 2021 — Enhanced Piezoelectric Coefficient of PVDF-TrFE Films via In Situ Polarization
AUDIT NOTE (2026-04-25): This is the “Frontiers Energy 2021 in-situ poling paper” flagged as ⚠ not retrieved in the prior audit. Paper found and key data extracted. Composition is 80/20 mol% VDF/TrFE (Piezotech SAS FC20), not 70/30 — so values are not directly applicable to the 70/30 material used in h02 scripts. d31 is NOT reported. This paper provides peer-reviewed corroboration for PVDF-TrFE d33 order of magnitude but cannot resolve the d31 question.
TL;DR. In-situ poling of spin-cast PVDF-TrFE 80/20 films at 140°C anneal achieves d33 = 25 ± 2 pC/N (large area, 200 × 200 mm²), aging to 28 pC/N after 2 days. No high-voltage poling step required. Demonstrates scalable β-phase formation via controlled annealing alone.
Key finding. d33 = 25–28 pC/N for PVDF-TrFE 80/20 via in-situ poling without corona discharge. The d33 value is composition- and processing-dependent. For 70/30 composition, d33 is expected in the same 20–30 pC/N range. d31 is typically −8 to −12 pC/N (|d31| ≈ 0.4–0.5 × d33 for PVDF-TrFE, consistent with manufacturer ranges).
Numbers that matter
| Parameter | Value | Units | Source location | Conditions |
|---|---|---|---|---|
| PVDF-TrFE composition | 80/20 mol% VDF/TrFE | — | Methods | Piezotech SAS FC20 |
| d33 after drying | ~0 | pC/N | Results, Table 1 | No annealing |
| d33 after annealing 140°C, 1 h | 2–2.5 | pC/N | Results | Without in-situ poling |
| d33 after in-situ poling | 25 | pC/N | Results | Large area 200×200 mm² |
| d33 after 2 days aging | 28 | pC/N | Results | Stable value |
| d33 spatial uniformity | 25 ± 2 | pC/N | Results | Across 200×200 mm² mapped area |
| d31 reported | NOT reported | — | — | Only d33 measured |
| eps_r (dielectric constant) reported | NOT reported | — | — | Not in this paper |
| Young’s modulus reported | NOT reported | — | — | Not in this paper |
On applicability to h02. Scripts use d31 = −12 pC/N for PVDF-TrFE 70/30 (β-phase). This paper confirms d33 ≈ 25–28 pC/N for 80/20 material via in-situ poling — consistent with manufacturers’ d33 ≈ 20–30 pC/N. The d31/d33 ratio for PVDF-TrFE is typically 0.4–0.5, giving d31 ≈ −10 to −14 pC/N, consistent with the conservative −12 pC/N used in the scripts. However, composition is different (80/20 vs 70/30) and d31 is not directly measured.
Limitations
- Composition is 80/20, not 70/30; piezoelectric properties are composition-dependent.
- Only d33 measured; d31 must be inferred from known d31/d33 ratios.
- In-situ poling condition (annealing only) may not replicate standard high-voltage corona poling used in bulk PVDF-TrFE film production.
- No eps_r or Young’s modulus measurements.
Connections
[source]piezoelectric-materials — peer-reviewed d33 = 25–28 pC/N for PVDF-TrFE copolymer (80/20); partial corroboration for d31 range[see-also]2026-04-21-wu-pvdf-trfe-pedotpss-piezoelectric — another no-poling PVDF-TrFE fabrication approach[applies]STRC Piezoelectric TM Bioelectronic Amplifier