Search

Single-phase delafossite-type CuMxLa1-xO2 (M=Mg, Ba, Ca, Sr, Mg, Zn, Cd) was synthesized by means of the solid-state reaction of a stoichiometrically mixed powder of binary oxides at 1273 K, for 10 h in an argon flow, and their luminescent properties were investigated. Undoped CuLaO2 exhibited a weak yellow-green photoluminescence-emission band due to the Cu+ interconfiguration transition at room temperature. The effect of II-group element doping on the photoluminescent properties was classified into two types. CuSrxLa1-xO2, CuBaxLa1-xO2 and CuZnxLa1-xO2 (x≤0.01) exhibited the emission slightly shifted to the shorter-wavelength side than that of undoped CuLaO2 and a strong emission intensity, with increasing doping concentration. These emission behaviors in CuSrxLa1-xO2, CuBaxLa1-xO2 and CuCaxLa1-xO2 was considered to be due to the formation of new emission centers upon doping Sr, Ba and Ca, respectively. CuZnxLa1-xO2, CuCdxLa1-xO2 and CuMgxLa1-xO2 (x≤0.01) exhibited the emission similar to one due to the Cu+ interconfiguration transition in undoped CuLaO2 and a weaker emission intensity, with increasing doping.

CuMxAl1-xO2 (M=Mg, Sr, Ca, Ba, Zn and Cd) ceramics have been prepared using a solid phase reaction method. The phase identification during synthesis was investigated using X-ray diffraction measurement. The thermoelectric properties such as the Seebeck coefficient (S), electrical conductivity (σ) and thermal conductivity of the ceramics were evaluated after sintering at 1423 K for 2 h in air. The power factor, S2σ, of CuMg0.005Al0.995O2 was approximately 1.6 × 10-5 W/K2m over a wide range of temperature of 650 to 900 K, which was the highest among all specimens prepared, and the value was approximately twentyfold larger than the value of CuA1O2.

Gels with nominal molar compositions of CaO⋅MgO⋅2SiO2 and CaO⋅MgO⋅1.95SiO2 using a mixture of each individual metal alkoxide were prepared without adding hydrochloric acid as a catalyst. The crystallization of CaMgSi2O6 (diopside) by heating the gels at various temperatures was investigated. Elemental analysis by EPMA showed the microscopic compositional nonuniformity of the metals in the gels. It was found from DTA-TG, XRD and FTIR analyses that calcium silicates firstly crystallized from a gel-like glass upon heating at temperatures below 1073K, beyond which CaMgSi2O6 formed as a predominant crystalline phase. This crystallization process was different from that observed for calcined powders of carbonate and oxides prepared by the conventional solid-state reaction method.