Effect of substrate thermal expansion coefficients on the properties of (Bi,Na)TiO₃–BaTiO₃ thick films around the morphotropic phase boundary

Abstract

Lead-free (1–x)(Bi0.5Na0.5)TiO3–xBaTiO3 (abbreviated as BNT–100xBT) thick films around the morphotropic phase boundary composition (0.03 ≤ x ≤ 0.09) were prepared on Pt-coated substrates with different thermal expansion coefficients, and the properties of the films were analyzed. While BNT–100xBT (x ≤ 0.05) exhibit a rhombohedral structure, BNT–100xBT (0.07 ≤ x) exhibit a tetragonal structure. The BNT–100xBT (0.03 ≤ x ≤ 0.09) thick films prepared on the MgO substrate preferentially formed c-domains. The Pr of the BNT–100xBT (0.03 ≤ x ≤ 0.09) thick films has the maximum value at the composition of x = 0.07 at room temperature. The depolarization temperature of the BNT–100xBT thick films prepared on MgO substrates with Pt bottom electrodes (0.05 ≤ x) was larger than that of the BNT–100xBT thick films prepared on 3 mol% Y2O3-stabilized ZrO2, Al2O3 substrates with Pt bottom electrodes, or bulk ceramics. An increase in the depolarization temperature became larger with an increase in composition of x because the thermal expansion difference between BNT–100xBT and MgO became large with an increase in the composition of x.

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.…”

“…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.…”

“…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. 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.…”

“…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.…”