Dielectric Properties of Alkoxy-Derived BaTiO3 Films on LaNiO3/Pt/TiOx/Si(100)
BaTiO3 films with higher degrees of (100) orientation were deposited using both of the heterogeneous LaNiO3 nucleation layer and homogeneous BaTiO3 buffer layer. The microstructure and dielectric properties are characterized. The temperature dependence of the dielectric properties is additionally discussed. The alkoxy-derived 1-mum thick BaTiO3 had the unique microstructure and showed predominant (100) orientation. The film showed ferroelectric to paraelectric transition around at 105degC, and improved dielectric properties. The improvement is considered to be due to the simultaneous control of crystallographic and microstructural characteristics by using the double nucleation and buffer layers.
Thickness Dependence of Electrical Properties of Highly (100)-Oriented BaTiO3 Thin Films Prepared by One-Step Chemical Solution Deposition
Highly (100)-oriented BaTiO3 thin films having different thicknesses of 70–280 nm were deposited on Pt/TiOx/SiO2/Si substrates with LaNiO3 as a buffer layer by one-step chemical solution deposition. X-ray diffraction analyses showed that the LaNiO3 and BaTiO3 layers were all under tensile stress. The tensile stress of the LaNiO3 layer increased after depositing BaTiO3 films. The tensile stress in both the LaNiO3 and BaTiO3 layers decreased with increasing BaTiO3 layer thickness. The thickness dependences of the dielectric and piezoelectric behaviors of the highly (100)-oriented BaTiO3 films were investigated. It was found that the effect of tensile stress on the dielectric and piezoelectric properties is dominant. A reduction in in-plane tensile stress (primarily arising from a thermal expansion mismatch) was considered effective for increasing the dielectric and piezoelectric constants. The measured dielectric constant increased from about 313 for 70 nm films up to 831 for 280 nm films. The local effective piezoelectric coefficient increased from 15 pm/V for 70 nm films up to 45 pm/V for 280 nm films.
Fabrication of PLLA/C3S Composite Membrane for the Prevention of Bone Cement Leakage
Kyphoplasty is an important treatment for stabilizing spine fractures due to osteoporosis. However, leakage of polymethyl-methacrylate (PMMA) bone cement during this procedure into the spinal canal has been reported to cause many adverse effects. In this study, we prepared an implantable membrane to serve as a barrier that avoids PMMA cement leakage during kyphoplasty procedures through a hybrid composite made of poly-l-lactic acid (PLLA) and tricalcium silicate (C3S), with the addition of C3S into PLLA matrix, showing enhanced mechanical and anti-degradation properties while keeping good cytocompatibility when compared to PLLA alone and most importantly, when this material design was applied under standardized PMMA cement injection conditions, no posterior wall leakage was observed after the kyphoplasty procedure in pig lumbar vertebral bone models. Testing results assess its effectiveness for clinical practice.