*2.2.3 Photocatalytic properties of Ba*2*Tb(Bi,Sb)O*<sup>6</sup> *samples*

We conducted the gaseous 2-propanol (IPA) and methylene blue (MB) degradation experiments, to evaluate photocatalytic activities of the powder samples (in detail, refer to [18, 29]). The visible light radiation experiment started after the IPA gas concentration reached constant under the dark condition. This conformation suggested that the IPA gas finished absorbing on the surface of powders. We used a 300 W Xe lamp equipped with UV and IR filtering functions (Cermax LX300F,

*Functional Materials Synthesis and Physical Properties DOI: http://dx.doi.org/10.5772/intechopen.100241*

### **Figure 4.**

*(a) Photocatalytic activities of IPA decomposition vs visible light irradiation time for Ba*2*TbBiO*<sup>6</sup> *citrate pyrolysis and solid-state samples. For comparison, the data for the Sb50% substituted sample are given. The gaseous concentration is normalized by the surface area of the powder samples. (b) Illuminating spectra of the Xe lamp limited in the visible wavelength range between 390 and 780 nm. (c) Photograph of 0.5-L glass reactor vessel for the IPA experiment. The powder sample (about 1 g) placed on the bottom of a small glass cell was set in its vessel.*

Excelitas Technologies). The illuminating spectra of the Xe lamp covered the visible wavelength range from 390 to 780 nm (**Figure 4b**). We set the powder samples (about 1 g) placed on the bottom of a small glass cell in a 0.5-L glass reactor vessel (**Figure 4c**) and injected the dilute IPA gas (5 cc) into its vessel with a syringe.

It is well known that the IPA gas under photocatalytic reaction is finally decomposed into CO2 [29]. Accordingly, the CO2 concentration was measured as a function of irradiation time using a gas chromatography system (GC-2014, Shimazu Co.). The photocatalytic methylene blue degradation was carried out using 0.5 g of powders suspended in 50 mL of MB solution (10 ppm). The MB solution was stirred in dark for 30 min before starting visible light radiation. The bleaching of MB was measured using the UV–visible spectrometer (V550, JASCO Co.). The solution of about 3 mL was transferred from the 100 mL reactor vessel under light irradiation and it was then analyzed at the regular time interval, to determine the corresponding MB concentration.

### **3. Results and discussion**
