Preparation and Sintering of Perovskite-Type Compound Powders by the Hydrazine Method

Submicron powders consisting of various kinds of perovskite-type compounds(PbZrO_3，LaCrO_3，LaCr_&lt；0.85&gt；Mg_&lt；0.15-x&gt；Co_xO_3(x=0，0.05，0.10)have been prepared by the hydrazine method。Characterization of powders have been performed using transmission electron microscopy，differential thermal analysis，thermal gravimetry，X-ray diffraction analysis，and BET method。LaCr_&lt；0.85&gt；Mg_&lt；0.15-x&gt；Co_xO_3powders have been sintered.Electrical and thermal properties of the sintered ceramics have been evaluated.1)PbZrO_3Metastable ZrO_2solid solutions containing up to 50mol%PbO are formed at low temperatures from as-prepared amorphous materials；the tetragonal phase up to 30mol%PbO and the cubic phase between30 and 50mol%PbO.The compound PbZrO_3is formed at 615óto 690°C by transformation of c-ZrO_2solid solution.2)LaCrO&lt；D23@&gt；2D LaastO&lt；D23@&gt；2D CrastO&lt；D&lt；D23@&gt；2D&lt；D&lt；D1515d Crito.D crat.The compound LaCrO&lt；@D23@&gt；D2 consisting of submicron powders(0.2mum)…More is formed at840°C by transformation of LaCrO&lt；@D24@&gt；D2.3)LaCr&lt；@D20.85@&gt；D2 Mg&lt；@D20.15-x@&gt；D2Co&lt；@D2x@&gt；D2O&lt；@D23@&gt；D2(x=0，0.05，0.10)As the same result as LaCrO&lt；@D23@&gt；D2，metastable LaCrO&lt；@D24@&gt；D2 solid solutions crystallize at low temperatures(()SYapprxeq[)480ºC)from as-prepared amorphous materials.LaCrO&lt；@D24@&gt；D2 solid solutions transform at(]SYapprxeq[)780°C C into the compounds LaCr&lt；@D20.85@&gt；D2 Mg&lt；@D20.15-x@&gt；D2Co&lt；@D2x@&gt；D2O&lt；@D23@&gt；D2(x=0，0.05，0.10)consisting of submicron powders(()SYapprxeq[)0.12mum)。After being calcined at 1000°C C for 1h，the powders compacted into pellets at 343 MPa have been sintered at 1600°C C for 2h。Well-densified compacts(()SYapprxeq[)95%of theoretical)can be obtained，although these compounds show poor sinterability。The LaCr&lt；@D20.85@&gt；D2 Mg&lt；@D20.15-x@&gt；D2Co&lt；@D2x@&gt；D2O&lt；@D23@&gt；D2ceramics obtained show high electric conductivity of(]SYapprxeq[)8.8S·cm&lt；@D1-1@&gt；D1at1000°C；this value is about ten times higher than than that of LaCrO&lt；@D23@&gt；D2ceramics reported.Thermal expansion coefficients of ceramics alpha are(]SYapprxeq[)11.3-12.0x10&lt；@D1-6@&gt；D1K&lt；@D1-1@&gt；D1in the temperature range between room temperature and 1000℃；the values are the same as c-ZrO&lt；@D22@&gt；D2.These results reveal that the LaCr&lt；@D20.85@&gt；D2 Mg&lt；@D20.15-x@&gt；D2Co&lt；@D2x@&gt；D2O&lt；@D23@&gt；D2 ceramics are suitable candidates for electrodes in solid oxide fuel cell(SOFC)composed of c-ZrO&lt；@D22@&gt；D2as a solid electroloyte。Less：Less

Submicron powders consisting of various kinds of perovskite-type compounds (PbZrO_3, LaCrO_3, LaCr_<0.85>Mg_<0.15-x>Co_xO_3 (x=0,0.05,0.10) have been prepared by the hydrazine method. Characterization of powders have been performed using transmission electron microscopy, differential thermal analysis, thermal gravimetry, X-ray diffraction analysis, and BET method. LaCr_<0.85>Mg_<0.15-x>Co_xO_3 powders have been sintered. Electrical and thermal properties of the sintered ceramics have been evaluated.1) PbZrO_3 Metastable ZrO_2 solid solutions containing up to 50 mol% PbO are formed at low temperatures from as-prepared amorphous materials ; the tetragonal phase up to 30 mol% PbO and the cubic phase between 30 and 50 mol% PbO.The compound PbZrO_3 is formed at 615ﾟ to 690ﾟC by transformation of c-ZrO_2 solid solution.2) LaCrO<@D23@>D2 Metastable LaCrO<@D24@>D2 crystallizes at (]SYgtoreq[)530ﾟC from as-prepared materials. The compound LaCrO<@D23@>D2 consisting of submicron powders (0.2mum) … More is formed at 840ﾟC by transformation of LaCrO<@D24@>D2.3) LaCr<@D20.85@>D2Mg<@D20.15-x@>D2Co<@D2x@>D2O<@D23@>D2 (x=0,0.05,0.10) As the same result as LaCrO<@D23@>D2, metastable LaCrO<@D24@>D2 solid solutions crystallize at low temperatures ((]SYapprxeq[)480ﾟC) from as-prepared amorphous materials. LaCrO<@D24@>D2 solid solutions transform at(]SYapprxeq[)780ﾟC into the compounds LaCr<@D20.85@>D2Mg<@D20.15-x@>D2Co<@D2x@>D2O<@D23@>D2 (x=0,0.05,0.10) consisting of submicron powders ((]SYapprxeq[)0.12mum). After being calcined at 1000ﾟC for 1h, the powders compacted into pellets at 343 MPa have been sintered at 1600ﾟC for 2h. Well-densified compacts ((]SYapprxeq[) 95% of theoretical) can be obtained, although these compounds show poor sinterability. The LaCr<@D20.85@>D2Mg<@D20.15-x@>D2Co<@D2x@>D2O<@D23@>D2 ceramics obtained show high electric conductivity of (]SYapprxeq[)8.8S・cm<@D1-1@>D1 at 1000ﾟC ; this value is about ten times higher than that of LaCrO<@D23@>D2 ceramics reported. Thermal expansion coefficients of ceramics alpha are (]SYapprxeq[)11.3-12.0x10<@D1-6@>D1K<@D1-1@>D1 in the temperature range between room temperature and 1000ﾟC ; the values are the same as c-ZrO<@D22@>D2. These results reveal that the LaCr<@D20.85@>D2Mg<@D20.15-x@>D2Co<@D2x@>D2O<@D23@>D2 ceramics are suitable candidates for electrodes in solid oxide fuel cell (SOFC) composed of c-ZrO<@D22@>D2 as a solid electroloyte. Less