Charge compensation and electrical characteristics of Ta2O5–doped SnO2–CoO ceramics. Issue 2 (February 2020)

• Record Type: Journal Article
• Authors: Tominc, Sara; Rečnik, Aleksander; Bernik, Slavko; Mazaj, Matjaž; Daneu, Nina
• Is Part Of: Journal of the European Ceramic Society. Volume 40:Issue 2(2020)
• Page Start: 355
• Page End: 361
• Publication Date: 2020-02
• Subjects: SnO2 ceramics -- Grain growth -- Point defects -- Rietveld analysis -- Electrical properties; Ceramic materials -- Periodicals; Composite materials -- Periodicals; Matériaux céramiques -- Périodiques; Composites -- Périodiques; Ceramic materials; Composite materials; Periodicals; Electronic journals; 666.05
• DOI: 10.1016/j.jeurceramsoc.2019.09.028
• Languages: English
• ISSNs: 0955-2219

Abstract

Abstract: We investigated the effect of pentavalent donor dopant Ta2 O5 on microstructure development, electric and dielectric characteristics of SnO2 –CoO based ceramics. Already low additions of Ta2 O5 (0.05 mol%) effectively reduce the porosity, improve densification and dielectric permittivity and trigger a 3–fold increase in SnO2 growth rate. Rietveld analysis shows that the amount of Co2 SnO4 spinel phase drops with the addition of Ta2 O5 due to incorporation of Co 2+ and Ta 5+ into SnO2 structure. With higher additions, however, Ta2 O5 segregates to the grain boundaries and hinders SnO2 grain growth, which in turn improves electrical properties. TEM/EDS analysis shows that above 0.5 mol% of Ta2 O5 the Co:Ta ratio in SnO2 grains is constant 1:2, which means that a twice lower amount of Ta 5+ is incorporated in the SnO2 structure compared to the Nb2 O5 -doped SnO2 –CoO system. Accordingly, the following charge compensation mechanism is proposed: 3 Sn(IV)S ˟ n (IV) ⇋ Co(II)Sn ̎(IV) + 2 Ta(V)˙Sn (IV) .