Hydroxyapatite Nano-Barium-Strontium-Titaniumoxide Composites

The aim of this study is to produce and to investigate the mechanical and microstructural properties of composite materials made of hydroxyapatite, obtained from natural bovine bone and nano barium strontium titanium oxide (5 and 10 wt%). Compositions were mechanical alloyed and compacted to pellets. The samples were subjected to sintering at different temperatures between 1000oC and 1300oC. Compression strength, Vickers microhardness as well as density were measured. SEM and X-ray diffraction studies were also conducted. With increasing sintering temperature, microhardness, compression strength and density of composites increased. With increasing addition of nano barium strontium titanium oxide (BST) to bovine hydroxyapatite (BHA), microhardness values of composites decreased at all sintering temperatures, but compression strength and density values of composites showed different tendency. Compression strengths of BHA-composites at low sintering temperatures were nearly the same, but their compression strengths at high sintering temperatures decreased with increasing nano BST addition. The best mechanical properties were obtained at 1300°C sintering temperature with BHA-5wt% nano BST. Microhardness and compression strengths values of these nano–oxide composites are generally higher than that BHA-composites produced by traditional methods. Adding of nano-oxides to BHA could be a valuable method to produce rigid and high load carrying ability when compared with BHA-composites produced by conventional methods. Nano-HA and nano-oxides composites could be even better. Those nano-nano studies are still in progress.

Influence of MgO Content on Microstructure and Dielectric Properties in (BaSr)TiO3 Ceramics

Barium strontium titanium oxide (BSTO) has great advantages and potentiality for the application of microwave technology. In order to be used in phased array antennas, high dielectric tunability, relatively low dielectric constant and low dielectric loss are required. In this paper, MgO was mixed into BSTO and the microstructure and dielectric properties of MgO-mixed BSTO bulk ceramics were investigated. The mole ratio of Ba and Sr was rather fixed to 5:5 in this study. It is observed that a small amount of MgO (5 wt%) has gone beyond the solubility limits of Mg in BSTO. The dielectric constant and dielectric loss of BSTO ceramics decreased with the increase of the content of MgO mixed. However, the tunability of MgO-mixed BSTO ceramics decreased at the same time. 20wt% MgO-mixed BSTO ceramics exhibits preferable dielectric properties with acceptable tunability.

Photo-Assisted Mocvd Growth of High Dielectric (Ba,Sr)TiO3 Thin Films on Ni/TiN/Si Substrate for Dram Application

High dielectric constant barium strontium titanium oxide (BST) thin films have been deposited on Ni/TiN/Si by photo-assisted metal organic chemical vapor deposition (PhAMOCVD). Planar capacitors based on the Ni/BST/Ni/TiN/Si heterostructure with BST-layer thickness of 50nm exhibited storage densities of about 30 fF/μm2 and leakage current densities of less than 10–7 A/cm2 under bias below 1.8V at room temperature. Nickel as a bottom electrode in this newly designed capacitor structure, can be easily patterned by reactive ion etching, and satisfies the requirement for integration with silicon.