Effect of Ho Content on Microstructure and Ferroelectric Properties of Bi_4−xHo_xTi₃O₁₂ Thin Films Prepared by Sol–Gel Method

Abstract

Bi4−xHoxTi3O12 (BHT‐x) thin films with Ho content x=0.2, 0.4, 0.6, 0.8, and 1.0 were prepared on Pt/Ti/SiO2/Si substrates by a sol–gel method. Effects of Ho contents on the microstructure and ferroelectric properties of BHT‐x thin films were investigated. All the BHT‐x samples consist of the Bi‐layered Aurivillius phase. The lattice constants along the a, b, and c axes decrease with the increase of x. The remanent polarization (2Pr) and dielectric constant (ɛr) increase firstly and then decreases with the increase of the Ho content, while the leakage current density shows opposite trend. BHT‐0.4 film exhibits the best electrical properties with 2Pr 44.2 μC/cm2, 2Ec 323.7 kV/cm, ɛr 489 (at 1 MHz), dielectric loss 0.018 (at 1 MHz), leakage current density 8.0 × 10−8 A/cm2 (under 200 kV/cm), as well as the strongest fatigue resistance (the polarization loss is only 3% after 4.46 × 109 switching cycles).

Bright Upconversion Emission, Increased Tc, Enhanced Ferroelectric and Piezoelectric Properties in Er‐Doped CaBi4Ti4O15 Multifunctional Ferroelectric Oxides

“…It is known that BLSFs are also important dielectric, ferroelectric, and piezoelectric materials that are widely used for high‐temperature sensors, thin‐film memory devices, and lead‐free piezoelectric resonators . As a member of bismuth‐layered pseudo‐perovskites, CBT is one of the candidates for application in dielectric, ferroelectric, piezoelectric and pyroelectric devices, filters, resonators, and micro‐electro‐mechanical systems …”

“…(a) shows that the dielectric loss was increased slightly with temperature, and the loss values for the doped samples are lower than that for the undoped one. This means that leakage current problems of the CBT system can be improved by introducing Er ions . With higher T c and lower dielectric loss tan δ, CBT_Er_ x ceramics can be regarded as a good candidate material for high temperature piezoelectric sensor applications …”

“…The series of BLSFs have stable chemical, mechanical, and thermal characteristics . Since the 1960s, the BLSFs have been intensively studied mainly for their potential applications in dielectric, ferroelectric, and piezoelectric fields . Because of their special crystal structure, the BLSFs have a large solubility of rare earth ions .…”

“…Because of their special crystal structure, the BLSFs have a large solubility of rare earth ions . It was found that their electric properties can be effectively modified by doping with rare earth elements such as La 3+ , Pr 3+ , Ce 3+ , Nd 3+ , Sm 3+ , Eu 3+ , Dy 3+ , Gd 3+ , Ho 3+ , etc . On the other hand, the rare earth elements mentioned above have been reported rare earth doped many other hosts as luminous centers to design a large number of luminescent materials for a wide range of applications .…”

Preparation and Ferroelectric Properties of Ho3+/Mo6+ Cosubstituted Bi4Ti3O12 Thin Films by Sol–Gel Method

“…[13][14][15] Our group reported a remarkable improvement of 2P r in the BTO films by adding Ho 3+ ions to the A sites. [16][17][18] However, the 2E c of Bi 3.6 Ho 0.4 Ti 3 O 12 (BHT) films became very large. It was suggested that A-site/B-site cosubstitution in BTO films could balance the P r and E c .…”