SOL-GEL COATING OF YBA2CU3O7-X WITH TIO2 FOR ENHANCED ANISOTROPIC GRAIN-GROWTH

This investigation focused on the effects of TiO2 additions (2.5-5 mol %) incorporated via sol-gel coating of powders on sintering behavior, microstructure development, electrical resistivity, and magnetic susc eptibility of YBa2Cu3O7-x. Specimens were sintered at less-than-or-equ al-to 960-degrees-C for 6 h in all cases. TEM analysis indicated the s ol-gel coating to be uniformly distributed around each particle and of thickness approximately 20 to 40 nm. The addition Of TiO2 was seen to reduce the sintering temperature by up to approximately 200-degrees-C , indicating the formation of a liquidus phase below that normally rep orted for YBa2Cu3O7-x. Grain growth and grain anisotropy behavior were influenced by TiO2 addition. A maximum in density, grain size, and an isotropy was achieved with 2.5 mol % addition sintered at 930-degrees- C. TiO2 addition was shown to result in the formation of greater amoun ts of secondary phases such as Y2BaCuO5 and BaCuO2, particularly at hi gher TiO2 levels and sintering temperatures. The use of TiO2 additions also altered the magnetic susceptibility with the optimum response oc curring for samples with 2.5 mol % TiO2 addition when sintered at 930- degrees-C.