Phase Relationships and Physical Properties of Homologous Compounds in the Zinc Oxide‐Indium Oxide System

Abstract

Equilibrium phase relationships in the ZnO-In 2 O 3 system were determined between 1100°and 1400°C using solidstate reaction techniques and X-ray diffractometry. In addition to ZnO and In 2 O 3 , nine homologous compounds, Zn k In 2 O k+3 (where k = 3, 4, 5, 6, 7, 9, 11, 13, and 15), were observed. Electrical conductivity and diffuse reflectance of the k = 3, 4, 5, 7 and 11 members were measured before and after annealing at 400°C for 1 h under forming gas (4% H 2 -96% N 2 ). Room-temperature conductivity increased as k decreased, because of increased carrier concentration as well as increased mobility. In general, transparency in the wavelength range of 450-900 nm increased as k increased. Reduction in forming gas resulted in increased conductivity and reduced transparency for all compounds measured. The highest room-temperature conductivity measured, 270 S/cm, was that of reduced Zn 3 In 2 O 6 .

Microstructure and thermoelectric characteristics of (ZnO)k×In2O3: Based ceramics (k = 5 and 11)

“…1 (JC PDF 00-020-1441) homologous phases were clearly detected, while the XRD pattern also indicates the possible formation of the phases for k ≥ 11 towards the pure ZnO phase, which could be identified in accordance with the report of Moriga et al [15] They also reported that only (ZnO) 5 (Fig. 2), with the largest having a length up to 5m and a thickness of approximately 0.8m.…”

Thermal (Kapitza) resistance of interfaces in compositional dependent ZnO-In2O3 superlattices

“…19 With further increases in solute concentration, individual InO 2 sheets form on the basal plane of ZnO and their spacing decreases until, at x ¼ 0.22 (k ¼ 7), a distinct, identifiable crystallographic compound Zn 7 In 2 O 10 forms. 18 So, in essence, a two-phase solid-solution region exists between pure ZnO and Zn 7 In 2 O 10 that according to the phase diagram persists up to 1175 C. (Above this temperature, a different superlattice spacing between the InO 2 sheets becomes stable. 18 ) While there remains some uncertainty as to the precise atomic arrangement in this compound, it is known to be rhombohedral (space group R3m ) and the InO 2 sheets are spaced 2.45 nm apart.…”

“…18 So, in essence, a two-phase solid-solution region exists between pure ZnO and Zn 7 In 2 O 10 that according to the phase diagram persists up to 1175 C. (Above this temperature, a different superlattice spacing between the InO 2 sheets becomes stable. 18 ) While there remains some uncertainty as to the precise atomic arrangement in this compound, it is known to be rhombohedral (space group R3m ) and the InO 2 sheets are spaced 2.45 nm apart.…”

“…18 As low concentrations of indium solute are added to ZnO, which is the usual range studied in the electronic doping of ZnO, the solute ion enters the crystal structure at random. 19 With further increases in solute concentration, individual InO 2 sheets form on the basal plane of ZnO and their spacing decreases until, at x ¼ 0.22 (k ¼ 7), a distinct, identifiable crystallographic compound Zn 7 In 2 O 10 forms.…”

In2O3-Based Thermoelectric Materials: The State of the Art and the Role of Surface State in the Improvement of the Efficiency of Thermoelectric Conversion

“…However, due to the low Seebeck coefficient, the maximum value of PF is only 0.85 mW/m·K 2 at 330 K. Approximately the same thermoelectric parameters were obtained for sintered ZnO ceramics doped with indium [113][114][115][116][117][118][119]. When the concentration of In 2 O 3 in ZnO was increased to 10 mol%, the thermal conductivity of ZnO:In decreased to~1.6-2.0 W/m·K, and the ZT in samples with optimal doping reached values of~0.1 at 1073 K. According to [109,116], the optimization of the thermoelectric parameters of metal oxides from the ZnO-In 2 O 3 and ZnO-Ga 2 O 3 systems is conditioned by the specificity of point defects [120][121][122], generated at low doping levels, and by the formation of Ga 2 O 3 (ZnO) m and In 2 O 3 (ZnO) m superlattice compounds in the Ga and In highly doped ZnO. Such superlattices belongs to the RMO 3 (ZnO) m type of homologous layered oxides [111,119,[121][122][123].…”