Syntéza a transportní vlastnosti La0.2Sr0.8Fe1.xTixO3.(x = 0.2, 0.4) vhodného pro produkci syntézního plynu

Synthesis and oxygen transport properties of La0.2Sr0.8Fe1.xTixO3.(x = 0.2, 0.4) intended for syn-gas production

journal article in Web of Science

en

Perovskites in the system La0.2Sr0.8Fe1-xTixO3-d exhibit high stability at severe reducing conditions and high temperatures. Due to favourable transport properties they are possible candidates both in oxygen permeation applications and anodes in SOFCs. Here we report the processing and oxygen transport properties of two different compositions: La0.2Sr0.8Fe1-xTixO3-d (x = 0.2, 0.4). Single phase powders were synthesized by both spray pyrolysis (SP) and solid state reaction (SSR). The resulting average particle sizes (BET) ranged from 140 nm (SP) to 1090 nm (SSR). Bar shaped samples were prepared by cold isostatic pressing and pressure less sintered between 1200 and 1250oC for 8-12 hours. Final sintered densities ranged from 97 (SSR) to 99% (SP) and grain size was less than 1.5 um. The average thermal expansion coefficients (TEC) varied in the range (13.8 – 14.6) .10-6K-1 at 300-600C and (21.3 – 28.9) .10-6K-1 at 600-800C. Surface exchange coefficients (kchem) and bulk diffusion coefficients (Dchem) in terms of temperature and pO2 were assessed by the method of electrical conductivity relaxation. A simple defect model was applied to explain electrical conductivity- and bulk diffusion behaviour.

Perovskitový systém na bázi La-Sr-Fe-Ti-O vykazuje vysokou stabilitu (chemickou i teplotní) i v přítomnosti redukční atmosféry a vysokých teplot. Na základě těchto studii je tento systém velmi dobrým kandidátem pro použití v jako komponenty v palivových článcích či jako výchozí materiál pro přípravu oxidových membrám. V této práci jsou disktutovány vlastnosti hutné keramiky připravené z keramických prášků – La0,2Sr0,8Fe0,8Ti0,2O3 a La0,2Sr0,8Fe0,6Ti0,4O3. Jsou popsány metodiky přípravy keramických prášků, vysokoteplotní reakce v tuhé fázi a sprejová pyrolýza, a jejich charakterizace pomocí RTG, SEM, BET. Dále je studován proces tvarování v hutnou keramiku a určení tepelné roztažnosti a stability při vyšších teplotách. Transportní chování bylo studováno pomocí určení celkové vodivosti materiálu v závislosti na jeho relaxaci ve směsi O2/N2.

Perovskites in the system La0.2Sr0.8Fe1-xTixO3-d exhibit high stability at severe reducing conditions and high temperatures. Due to favourable transport properties they are possible candidates both in oxygen permeation applications and anodes in SOFCs. Here we report the processing and oxygen transport properties of two different compositions: La0.2Sr0.8Fe1-xTixO3-d (x = 0.2, 0.4). Single phase powders were synthesized by both spray pyrolysis (SP) and solid state reaction (SSR). The resulting average particle sizes (BET) ranged from 140 nm (SP) to 1090 nm (SSR). Bar shaped samples were prepared by cold isostatic pressing and pressure less sintered between 1200 and 1250oC for 8-12 hours. Final sintered densities ranged from 97 (SSR) to 99% (SP) and grain size was less than 1.5 um. The average thermal expansion coefficients (TEC) varied in the range (13.8 – 14.6) .10-6K-1 at 300-600C and (21.3 – 28.9) .10-6K-1 at 600-800C. Surface exchange coefficients (kchem) and bulk diffusion coefficients (Dchem) in terms of temperature and pO2 were assessed by the method of electrical conductivity relaxation. A simple defect model was applied to explain electrical conductivity- and bulk diffusion behaviour.

vysokoteplotní reakce v tuhé fázi, sprejová pyrolýza, elektrické vlastnosti, objemová expanze, perovskity

Powders-solid state reaction, spray pyrolysis, electrical properties, thermal expansion, perovskites

2009

07.10.2009

ELSEVIER SCI LTD

THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND

0955-2219

Journal of the European Ceramic Society

30

2

605–611

7