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The most alumina-rich compound in the CaO-Al2O3 system is calcium hexaaluminate (CaAl12O19, CA6). CA6 ceramics were synthesized by the sol-gel auto combustion method. CA6 phase formation has been achieved at 1200°C, which is a much lower temperature than the convention process (>1600°C). The influence of Sr2+ substitution on the densification of Ca1-xSrxAl12O19 (x = 0, 0.1, 0.2, and 0.3) ceramics was investigated. The X-ray diffraction analysis and structural refinement indicated the substitution of Sr2+ ions into the lattice of CA6. The elongation of the “c” direction of the CA6 crystal structure was found with Sr2+ ion substitution. Surface morphology analysis showed a crystal growth with Sr2+ substitution in CA6 upto x = 0.2 composition. The 1600°C sintered specimen (with x = 0.2 composition) showed the bulk density and open porosity of 3.39 g/cm3 and 4.92%, respectively. Thus, auto combustion synthesis and Sr2+ substitution into CA6 ceramics are feasible and beneficial for the densification of the ceramics.

BaFe12O19 (BaM) hexagonal ferrite was synthesised through the co-precipitation route. The thermal decomposition behaviour of co-precipitated powder was studied by DSC-TG. XRD and Raman analysis con...

Scaffolds for bone tissue engineering should be designed with adequate porosity, mechanical properties and biocompatibility. In the present investigation, the titania (TiO2) containing glass-cerami...

Macroporous composite scaffolds comprising of gelatin and glass ceramic has been fabricated and characterized for bone tissue engineering applications. Gelatin scaffold with varying glass-ceramic content was fabricated using lyophilization technique. The microstructure, compressive strength, bioactivity, biodegradation and biocompatibility of the fabricated scaffolds were evaluated. The scaffolds presented macroporous pore size with porosity varying from 79 to 84%. The compressive strength was enhanced by glass ceramic addition and the scaffolds exhibited strength in the range of 1.9 to 5.7 MPa. The obtained strength and porosity was in the range of cancellous bone. The dissolution of gelatin scaffolds was optimized by an additional in situ glutaraldehyde crosslinking step and further by glass-ceramic addition. The composite scaffolds showed good apatite-forming ability in vitro. Biocompatibility and osteogenic ability of the scaffolds were analyzed in vitro by cell adhesion study, alkaline phosphatase activity and Alizarin S staining. The obtained results revealed the composite scaffolds possessed enhanced osteogenic ability and good cell adhesion properties. The developed scaffold is a prospective candidate as a biomaterial for bone tissue engineering.

Phase-pure KNN (K0.5Na0.5NbO3) was synthesized from Rochelle salt and niobium pentoxide through solid-state route and the synthesized powder was sintered at 1130°C to get dense KNN ceramics. After polarization fatigue test, it was found that the d33, kP and remanent polarization (Prem) of KNN decreased substantially. The reduction of the aforesaid parameters after fatigue was much higher in comparison to that of soft PZT (Navy type VI) tested under identical conditions. The possible reason behind such behaviour has been delineated.

In this study, Bi4Ti3O12–SrBi4Ti4O15 (BIT–SBTi) intergrowth ferroelectric ceramics was synthesized by a modified oxalate route. The phase formation behaviour, structure, morphology and electrical properties of the intergrowth ceramics were also investigated. The phase formation takes place through intermediate phases like SrBi2O4 and Bi12TiO20. The precursor mostly changes to Bi4Ti3O12 at 600°C and to BIT–SBTi intergrowth at 800°C. Rietveld analysis of the X-ray diffraction pattern showed that the structure of the intergrowth compound was orthorhombic with lattice parameters a = 5.4408(3), b = 5.4505(1) and c = 74.0851(4) A. The intergrowth ferroelectrics showed a phase transition at 610°C and a frequency-stable permittivity and dielectric loss behaviour. The intergrowth ferroelectrics also showed a larger 2Pr than their constituents BIT and SBTi.

Ba(Ti1-xZrx)O3 ceramic powders were prepared by solid state reaction. The mono phase powders were then used to produce nano powder using high-energy ball milling. The crystallite sizes of each composition were investigated by varying the milling speed from 150 to 350 rpm fixing the milling time at 10 h and the milling time from 10 to 90 h, at a fixed speed of 250 rpm. X-ray diffraction analysis of the powder showed the single phase perovskite structure of Ba(Ti1-xZrx)O3 powders. The increase in milling speed and milling time showed reduction of crystallite size to a minimum value which increases with further increase in milling time. FTIR analysis of Ba(Ti1-xZrx)O3 ceramic powders before and after ball milling illustrated a change in force constant of M-O bond.

Silica ceramics were prepared using three types of raw materials derived from rice husk. Cleaned husk and acid-leached husk were burned at 700°C to get brown ash (BA) and white ash, respectively. The third type was silica gel (SG) derived from BA through the alkaline extraction of silica from ash followed by acid neutralization. Granulated powders were pressed and pellets were sintered at 700–1400°C range. Phase-formation behavior, densification characteristics, and mechanical strength of ceramics were investigated and correlated with microstructural features. Ceramics made of SG showed the highest density and mechanical strength among all. All the ceramics were initially amorphous and transformed into crystalline silica above a specific sintering temperature. Microstructure shows the formation of cracks in the ceramics when they contain cristobalite phases. Amorphous-to-crystalline phase transformation temperature in different types of silica source was dependent on the amount of impurity and residual hy...

Impedance spectroscopy has been used to characterize grain and grain-boundary resistivities of Ni-doped SrTiO 3 ceramics. The role of grain boundary was changed with Ni-doping concentration. The phenomenon was also interpreted by accounting for microstructural differences. The corresponding relaxation times were also used to confirm the interpretation of complex impedance spectra. Overlapping of Grain boundary and electrode relaxation processes can be separated above about 400°C. Admittance spectra may be suitable to extract grain boundary impedances at relatively low temperatures. The values of grain and grain-boundary activation energy obtained by this method were relatively close to those reported earlier.

Using BaTiO 3 based Z5U material and silver-palladium internal electrode, multilayer ceramic capacitors (MLC) were fabricated. The MLC had 24 effective dielectric layers, thickness of one layer was about 20 μm and the capacitance was 0.1 μF. Formation of green chips, binder burnout, sintering, terminations of electrode were described. Internal structure showed no de-lamination between electrode/dielectric interfaces. Surface microstructure of dielectrics depicted average grain size of about 6-7 pm. Temperature dependence of capacitances and tan δ were investigated. The MLC had very high resonant frequency ∼2.1 MHz and very low ESR -3.6 Ω.