Effect of substrate material to the properties of screen-printed lead free (Bi_0.5Na_0.5)TiO₃-based thick films

Abstract

Lead-free piezoelectric 0.83(Bi0.5Na0.5)TiO3-0.17BaTiO3 (BNT-17BT) thick films were grown on MgO ceramic substrates via screen printing. Thick films with compressive stress formed a c-domain preferentially with a volume fraction of 0.88. High-temperature X-ray diffraction and piezoresponse force microscopy and the temperature dependence of the piezoelectric coefficient d33 data indicated that the thick films had a preferred c-domain during the transformation from the tetragonal phase to the cubic phase with temperature increasing. Based on polycrystalline MgO substrates with high thermal expansion coefficients, the thick films displayed a higher phase transition temperature and larger remanent polarization (Pr) values over 220 °C than those of thick films on Al2O3 substrates. The ferroelectric properties of BNT-17BT/MgO were better than those of soft PZT/YSZ and hard PZT/YSZ over 220 °C. The results showed the possibility of applying BNT-17BT thick films in a wide temperature range.

Effect of MnO2 addition on temperature-dependent properties of tetragonal (Bi,Na)TiO3–BaTiO3 thick films prepared on MgO ceramic substrates

“…Therefore, we have already prepared lead-free BNT-100xBT (x = 0.03, 0.05, 0.07, 0.09, and 0.17) thick films using screen printing. [30][31][32] In this study, we found that the residual compressive stress caused an increase in T d of the BNT-100xBT thick films, which results in higher T d of the thick films on MgO substrate than that of bulk ceramics or thick films on YSZ or Al 2 O 3 substrates. 30,31) The BNT-100xBT thick films with composition near the MPB (0.05 ⩽ x ⩽ 0.07) exhibited a large P r of ∼16 μC cm −2 at room temperature, whereas the increase in T d is restrictive because the thermal expansion of the BNT-100xBT (0.05 ⩽ x ⩽ 0.07) are close to that of MgO substrates.…”

“…[30][31][32] In this study, we found that the residual compressive stress caused an increase in T d of the BNT-100xBT thick films, which results in higher T d of the thick films on MgO substrate than that of bulk ceramics or thick films on YSZ or Al 2 O 3 substrates. 30,31) The BNT-100xBT thick films with composition near the MPB (0.05 ⩽ x ⩽ 0.07) exhibited a large P r of ∼16 μC cm −2 at room temperature, whereas the increase in T d is restrictive because the thermal expansion of the BNT-100xBT (0.05 ⩽ x ⩽ 0.07) are close to that of MgO substrates. At the composition of x = 0.17, the increase in T d (>100 °C) is larger than that of the thick films near the MPB composition (30 °C-70 °C) because of their large thermal expansion difference.…”

“…Under compressive stress, the c-axis in the thick films tends to be perpendicular to the substrate when the phase transition from the cubic to the tetragonal phases occurs. 16,[30][31][32] Therefore, the preferential c-axis orientation of the thick films in Fig. 5 indicates the presence of compressive stress in the thick films.…”

“…Screen-printable paste was prepared in the same manner as in the previous work. [30][31][32] MgO ceramic substrates (16 mm × 26 mm × 0.5 mm) were used in this study because MgO shows a large thermal expansion coefficient. 31) The Pt bottom electrodes patterns (12 × 16 mm 2 ) were prepared by screen printing and firing at 1350 °C for 1 h. The array of the BNT-100xBTyMn thick film with a 3 × 3 mm 2 area was fabricated as follows.…”

“…31) However, the P r of BNT-17BT thick films at room temperature was relatively low at 10 μC cm −2 . 30,31) Therefore, an improvement of the thick films' electrical properties at room temperature with high T d is required. Mn addition improves the electrical properties of BNT-100xBT and its related materials.…”