Preparation and Electrical Properties of Highly (111)-Oriented (Na_0.5Bi_0.5)TiO₃ Thin Films by a Sol−Gel Process

Abstract

Sodium bismuth titanate, (Na0.5Bi0.5)TiO3 (NBT), thin films were grown on Pt/Ti/SiO2/Si substrates via a sol−gel process. The precursor solution for spin-coating was prepared from bismuth nitrate, sodium acetate, and titanium n-butoxide as starting materials, and acetic acid and methanol as solvents, and pervoskite NBT films with high (111)-orientation have been obtained. The Au/NBT/Pt thin film capacitor showed a hysteresis loop at an applied electric field of 200 kV/cm with remanent polarization (P r) and coercive electric field (E c) values of 20.9 μC/cm2 and 112 kV/cm, respectively. At 100 kHz, the dielectric constant and loss tan δ of the film were 171 and 0.024, respectively. The leakage current depended on the voltage polarity. When an electrical field ranges from 0 to 167 kV/cm and with the Pt electrode biased negatively, the NBT/Pt interface exhibits a Schottky emission characteristic. The Au/NBT interface forms an ohmic contact. The conduction current when the Au electrode is biased negatively shows space-charge-limited current (SCLC) behavior.

Dielectric and Pyroelectric Properties of Lead-Free Sodium Bismuth Titanate Thin Films Due to Excess Sodium and Bismuth Addition

“…The films contained mixed phases including the pyrochlore Bi 2 Ti 2 O 7 (BTO) and the perovskite NBT. Many studies of the preparation of bulk ceramics 10) and thin films 6) have reported that the preferred pyrochlore BTO phases are often created. As shown in Fig.…”

“…3,4) However, it has been reported that a stable single perovskite NBT phase is not easy to prepare due to the relatively low tolerance factor t ~ 0.799 and volatility of Na and Bi. 5,6) These problems result in the creation of secondary phases and the degradation of electrical performance. So until recently, various processes such as the compositional compensation and/or the ambient control have been widely reported with the aim of preparing pure perovskite NBT films.…”

“…So until recently, various processes such as the compositional compensation and/or the ambient control have been widely reported with the aim of preparing pure perovskite NBT films. [6][7][8] In the case of sputtered NBT films, various techniques such as NBT powder bedding process and oxygen atmospheric annealing have been tested. 8,11) In chemically wet processes, excessive Bi addition or excessive Na addition through control of the concentration of Na or Bi source have often been reported.…”

“…8,11) In chemically wet processes, excessive Bi addition or excessive Na addition through control of the concentration of Na or Bi source have often been reported. 6,7,10,12,13) A-site substitution has been employed with other materials with high tolerance factors such as BaTiO 3 and PbTiO 3 to improve their electrical properties by enhancing the purity of the perovskite phase. 14,15) However, there are few studies regarding the relations between the amount of crystalline phases present in NBT thin films and their dielectric properties due to excessive addition of Na and Bi.…”

Enhanced ferroelectric and piezoelectric properties in doped lead-free (Bi0.5Na0.5)0.94Ba0.06TiO3 thin films

“…[5][6][7] In spite of the numerous studies on BNT-based single crystals and ceramics, literature tackling with the growth and characterization of BNT-based, especially BNBT-based thin films, still remains at an infancy stage. [8][9][10][11][12] Consequently, doping effects on the electrical properties of thin film BNBT materials are still unclear. Abazari et al 13 has recently reported epitaxial potassium modified BNBT thin films grown on SrRuO 3 coated SrTiO 3 substrates by pulsed laser deposition ͑PLD͒.…”