Large electrostrain in low‐temperature sintered NBT‐BT‐0.025FN incipient piezoceramics

Abstract

It is well‐known that the high sintering temperatures of (Na1/2Bi1/2)TiO3 (NBT)‐based incipient piezoceramics limit their applications on low‐cost multilayer piezoelectric actuators with base metal internal electrodes. In this work, a synergistic sintering additive of 0.75 wt% Li2CO3 and 0.75 wt% CuO was utilized to explore the effect on sintering behavior and electrostrain of (Na1/2Bi1/2)0.935Ba0.065Ti0.975(Fe1/2Nb1/2)0.025O3 (NBT‐BT‐0.025FN) incipient piezoceramic. The optimal sintering temperature of NBT‐BT‐0.025FN decreased from 1160°C to 940°C due to the formation of a liquid phase, with limited degradation on electrostrain. When sintered at 940°C, a large strain of 0.39% (a nominal piezocoefficient d33∗ of 571 pm/V) was achieved, which is promising for potential actuator applications co‐firing with Ag electrodes.

Novel BaTiO3-Based, Ag/Pd-Compatible Lead-Free Relaxors with Superior Energy Storage Performance

“…A-site deficient x Bi 2/3 (Mg 1/3 Nb 2/3 )­O 3 –(1 – x )­BaTiO 3 ( x B 2/3 MN-BT) ceramics, with ( x = 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10) solid solution were synthesized using a conventional solid–state reaction with analytical-grade raw powders of BaCO 3 (>99.5%), TiO 2 (>99.9%), MgO (>99.9%), Nb 2 O 5 (>99.5%), and Bi 2 O 3 (>99.9%). Excess 0.5 mol % Bi 2 O 3 was added to compensate for Bi-loss during processing and Li 2 CO 3 was used as a fluxing agent to reduce the sintering temperature. − Mixed powders were ball milled for 16 h, dried, and calcined 2 h at 900 °C. After calcination, the mixed powder was ball milled for 16 h, dried, and uniaxially pressed into 10 mm diameter pellets, followed by sintering 4 h from 1050–1200 °C.…”

Superior Large-Signal Piezoelectric Coefficient in Textured NBT-Based Piezoceramics by Template-Induced Structure and Composition Modulation

“…In addition, the effects of CuO and Li 2 CO 3 aids on the strain properties of the randomly oriented NBT-BT-FN ceramic matrix have been investigated in our previous work. 30 The aids can achieve simultaneously almost unchanged strain characteristics as well as a reduction in sintering temperatures, which indicates that the ceramic matrix maintains the initial relaxor−ferroelectric phase. However, under the electric field of 40 kV/cm, slightly higher strain values can be found for the liquid phase 960 °C-textured ceramic than for the regularly 1150 °C-textured one (Figure 6c), which may be ascribed to the dissolution of the templates.…”

“…To realize this concept, in this work, we applied the T G G a p p r o a c h t o f a b r i c a t e a ⟨ 0 0 1 ⟩ -t e x t u r e d (Na 0.5 Bi 0.5 ) 0.935 Ba 0.065 Ti 0.978 (Fe 0.5 Nb 0.5 ) 0.022 O 3 ceramic (abbreviated as NBT-BT-2.2FN) with a small amount of Li 2 CO 3 and CuO as sintering aids to assist template-induced grain growth, where the ⟨001⟩-oriented NN microplates were used as templates. 25,30 The NBT-BT-2.2FN solid solution was found to be a nonergodic relaxor state and therefore chosen as the matrix. 30−32 The results demonstrated that the liquid phase caused by the additions of Li 2 CO 3 and CuO could significantly facilitate the growth of NBT-BT-2.2FN single crystals on platelike NN particles, yielding a very high F 00l of 95% at a low sintering temperature (1000 °C) in the textured ceramics.…”

“…Afterward, the composition of the initial matrix is designed to display a softened ferroelectric activity, i.e., a nonergodic relaxor (NR) state, which can drive the textured NBT-based ceramic to exhibit a reversible phase transition at room temperature, and Figure shows the schematic diagram of this synergistic strategy. To realize this concept, in this work, we applied the TGG approach to fabricate a ⟨001⟩-textured (Na 0.5 Bi 0.5 ) 0.935 Ba 0.065 Ti 0.978 (Fe 0.5 Nb 0.5 ) 0.022 O 3 ceramic (abbreviated as NBT-BT-2.2FN) with a small amount of Li 2 CO 3 and CuO as sintering aids to assist template-induced grain growth, where the ⟨001⟩-oriented NN microplates were used as templates. , The NBT-BT-2.2FN solid solution was found to be a nonergodic relaxor state and therefore chosen as the matrix. − The results demonstrated that the liquid phase caused by the additions of Li 2 CO 3 and CuO could significantly facilitate the growth of NBT-BT-2.2FN single crystals on plate-like NN particles, yielding a very high F 00 l of 95% at a low sintering temperature (1000 °C) in the textured ceramics. Intriguingly, due to the promotion of the liquid phase, the NN templates gradually dissolved into the oriented grains during the sintering process and the textured ceramic displayed a similar phase structure to the NN-doped nontextured counterpart.…”

Boosting the High Performance of BiFeO3-BaTiO3 Lead-Free Piezoelectric Ceramics: One-Step Preparation and Reaction Mechanisms

“…Another hurdle for BF- x BT ceramics is that the optimal T sint is usually higher than 1000 °C, which is also higher than the melting point of BiFeO 3 (930 °C). ,− Bi 3+ is prone to volatilization at elevated temperatures during sintering due to its high saturated vapor pressure, resulting in deviations from the optimal combination and higher conductivity . A low T sint also has cofiring advantages, including the use of cheaper internal electrodes and lower energy consumption in multilayer devices. − Therefore, low-temperature sintering is attractive to expanding the application of BF- x BT ceramics. Considerable efforts have been put into studying the role of sintering additives in the BF- x BT system.…”