Effect of sintering temperature on the thermoelectric properties of NaxCo2O4

Advantages of Low Partial Pressure of Oxygen Processing of Alkali Niobate: NaNbO3

“…The UV–vis diffuse reflectance was performed to determine the optical band‐gap energy of each calcined powder. The Kubelka–Munk equation, F ( R ) = (1 − R ) 2 /2 R = α/ s ( R , relative reflectance; α, absorption coefficient; s , scattering coefficient), was used to determine the optical absorbance curves. The optical reflectance curves were taken to form a Tauc plot of F ( R ) h n against photon energy by using the Tauc equation, [ F ( R ) hv ] n = A ( E g − hv ), where A is a proportionality constant with regard to a material, and E g is the band‐gap energy of a material; the value of the index n depends on the electronic transition (direct n = 2; indirect n = 1/2).…”

“…The pure NN ceramics were prepared without use of any sintering additives using the low-pO 2 process, and the microstructure and dielectric and ferroelectric properties were investigated and compared to those of conventional calcination and firing process in air atmosphere. This example may then be of interest to a broader number of materials in the functional oxide family that involve processing difficulties with alkali volatility, such as the thermoelectric oxide NaCoO 4 , [24][25][26] and other ferroelectrics NaTaO 3 , KTaO 3 , and KNbO 3 . 1,[27][28][29][30][31][32]…”

Thermoelectric properties of Cu1−xPtxFeO2 (0.0≤x≤0.05) delafossite-type transition oxide

“…Recently, thermoelectric properties of oxide materials have been shown conversion efficiency close to that of conventional semimetallic materials. For example, thermoelectric voltage and direct current conductivity of transition-metal oxides such as NiO, NaCo 2 O 4 and Ca 3 Co 4 O 9 have been reported to be large at high temperature conditions [5][6][7][8]. In addition, CuFeO 2 compound with delafossite structure has been reported to exhibit a large value of S (544 V/K) and PF (0.44 × 10 4 W/mK 2 ) [9].…”

The effect of synthesis technique on thermoelectric properties of nanocrystalline NaCo2O4 ceramics

“…The sharp peaks seen in Fig. 3 suggest that the obtained samples are predominantly of c-phase NaCo 2 O 4 (Cheng et al 2006;Nakatsugava and Nagasawa 2004;Park and Lee 2008;Ito and Furumoto 2008;Seetawan et al 2006). The X-ray results also exhibit that there are relatively small amounts of Co 3 O 4 present in the samples which is probably due to sodium evaporation during the calcination process at 850°C (Ma et al 2010).…”