Synthesis of BaSm_2Ti_4O_(12) via Polymeric Precursor method

A polymeric precursor method by using citric acid as the chelating agent was invesi- gated and single-phase and well-crystallized BaSm_2Ti_4O_(12) powder was synthesized at 1000℃for 3h.As a comparison,an oxalate co-precipitation method was applied to synthesize BaSm_2Ti_4O_(12) powder,but 1300℃was needed to get the pure BaSm_2Ti_4O_(12).The different phase behavior and reaction sequences are here believed to answer for the different calcining temperatures needed via these two wet chemical methods.In the co-precipitation method,when heating the precipi- tate,intermediate phase Sm_2Ti_2O_7 reacts with BaTi_4O_9 and BaTiO_3 to produce BaSm_2Ti_4O_(12), which is similar to the sohd-state route.As to the polymeric precursor route,however,BaTi_2O_5 intermediate phase produces during the thermal decomposition process,which results in totally different reaction sequences from the solid-state reaction mechanism,and promotes the formation of BaSm_2Ti_4O_(12) phase.