Sintering of undoped SnO2

Abstract

Pure SnO 2 sintering was studied by constant heating rate and isothermal sintering. The constant heating rate study showed no macroscopic shrinkage during the sintering process up to 1500 o C. Pore size distribution measurements, using gas desorption, and grain size and crystallite size measurements of isothermally sintered samples showed no formation of nondensifying microstructures during the sintering process. These results are a strong indication that densification was prevented by thermodynamic factors, mainly the high ratio of γ GB /γ SV . An explanation, based on the nature of covalent bonding and the balance between attractive and repulsive forces, was proposed to explain the high γ GB /γ SV ratio in SnO 2 .

Simultaneous Doping of Zn and Sb in SnO2 Ceramics: Enhancement of Electrical Conductivity.

“…Consistent with literature [19][20][21], no significant macroscopic shrinkage was observed for undoped ceramics by sintering at 1300 • C. The bulk density (4.12 g/cm 3 ), corresponds to 58% of the theoretical value (6.95 g/cm 3 ), as shown in Table 1. It should be noted that the n-type conductivity, normally observed in undoped SnO 2 , is due to the co-existence of oxygen vacancies ( ) and interstitial tin (Sn i ), occurring simultaneously and producing shallow donor levels [11].…”

“…Unfortunately, the use of SnO 2 ceramics is limited by the low densification of this oxide during sintering. Indeed, Leite et al [19,20] and Varela et al [21] reported no significant macroscopic shrinkage during sintering, even at up to 1300 • C. However, a meaningful shrinkage, associated with high densification, is possible by addition of cationic dopants with oxidation states lower than Sn 4+ , such as Mn 2+ , Cu 2+ , Zn 2+ or Co 3+ [22][23][24]. In this work SnO 2 was doped with both Zn 2+ and Sb 5+ ions in order to obtain dense ceramics with high electrical conductivities.…”

'Parking' and packing problems in particulate materials processing

“…19 the pore size distributions are lognormal; this figure includes data from zirconia, tin oxide and alumina bodies. [35][36][37] The behaviour is as expected from the random assembly process.…”

“…17 Small packing density increase accompanies segment agglomeration due to short range attractive force: this plot gives packing density versus distance parameter (from 0?0 to 0?1) that induces segment attractive rearrangement a zirconia; 35 b alumina; 36 c tin oxide 37 19 Three examples of lognormal pore size distribution in powder structures as expected based on random parking structure used in forming green bodies 2. Lognormal size distributions best describe the unfilled void space corresponding to the pore size distribution.…”

Surfactantless synthesis and textural properties of self-assembled mesoporous SnO2

“…Before proceeding into the morphological interpretation of our sorption results, it would be very useful to remember the main conclusions that have been reached with respect to the structural evolution of undoped SnO 2 xerogels during sintering [20,21]. First, desiccated SnO 2 gels (110 • C) have been seen to consist of nanocrystallites possessing an incipient cassiterite structure.…”