The interaction between silver nitrate and niobium pentoxide has been studied under conventional thermal treatment (TT) as well as mechanochemical and sonochemical treatment (MChT and UST, respec-tively). The products of reaction have been investigated using XRD, DTA-TG, Raman spectroscopy, adsorp-tion of nitrogen. MChT and UST promote lowering the temperature of silver niobate (SN) formation. The formed SN possesses higher specific surface area and photocatalytic activity.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3527

Khalameida, S.

Leboda, R.

Skubiszewska-Zięba, J.

Starchevskii, V.

Sydorchuk, V.

Zakutevskii, O.

Zazhigalov, V.

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 2 No 1, 01PCSI12 (3pp) (2013) 
 
 
2304-1862/2013/2(1)01PCSI12(3) 01PCSI12-1  2013 Sumy State University 
Synthesis and Photocatalytic Properties of Silver Niobate 
 
V. Sydorchuk1, S. Khalameida1, J. Skubiszewska-Zięba2, R. Leboda2, V. Starchevskii 3, V. Zazhigalov1, 
O. Zakutevskii1 
 
1 Institute for Sorption and Problems of Endoecology National Academy of Science of Ukraine, 13, Naumov Str., 
03164, Kyiv, Ukraine 
2 Faculty of Chemistry, Maria Curie-Sklodowska, 3, pl. Marie Curie-Sklodowska, 20031, Lublin, Poland 
3 Department of General Chemistry, Lviv Polytechnic National University, 12,  Bandera Str., 79013, Lviv, Ukraine  
 
(Received 30 May 2013; published online 1 September 2013) 
 
The interaction between silver nitrate and niobium pentoxide has been studied under conventional 
thermal treatment (TT) as well as mechanochemical and sonochemical treatment (MChT and UST, respec-
tively). The products of reaction have been investigated using XRD, DTA-TG, Raman spectroscopy, adsorp-
tion of nitrogen. MChT and UST promote lowering the temperature of silver niobate (SN) formation. The 
formed SN possesses higher specific surface area and photocatalytic activity.  
 
Keywords: Silver Niobate,  Milling, Sonochemichal Treatment, Photocatalytic Activity. 
 
 PACS number: 42.70.Qs 
 
 
1. INTRODUCTION 
 
The development of photocatalysts with visible-light 
response has been studied extensively from the view-
point of the utilization of solar light energy including 
for degradation of pollutants in air and water. Such 
ferroelectric material as silver niobate AgNbO3 pos-
sessing the perovskite structure is a potential photo-
catalyst [1, 2]. The AgNbO3 samples were usually pre-
pared using a solid-state reaction method by mixing 
powders of Ag2O and Nb2O5 in nonstoichiometric ratio, 
followed by a pre-heat treatment at 800 C for 4 h and 
then calcination at 970 C for 7 h in air [3]. In this 
work, we studied the influence of preliminary sono- and 
mechanochemical activation of reaction mixture Ag-
NO3+Nb2O5 on structure and catalytic properties of 
AgNbO3. 
 
2. EXPERIMENTAL PROCEDURE 
 
2.1 Silver niobate synthesis 
 
Silver nitrate and niobium pentaoxide with differ-
ent specific surface area (2 and 355 m2·g-1) were used as 
initial reagents. These mixtures were subjected to ul-
trasound and mechanochemical treatment (UST and 
MChT, respectively) in water and air. Activated prod-
ucts (precursors) were additionally calcined at 450 and 
600 C. 
 
2.2 Physical-chemical characterization 
 
The phase composition was studied by means of X-
ray powder diffraction (XRD) using Philips PW 1830 
diffractometer with CuKα-radiation. The primary crys-
tallites size Dhkl was calculated using the broadening of 
the most intensive lines according to Sherrer’s equa-
tion. Curves of DTA and TG were recorded using Deri-
vatograph-C apparatus (F.Paulik, J.Paulik, L.Erdey) in 
the range of temperature 20-600 C at the heating rate 
10 /min. Initial mass of sample was 200 mg. Diffuse 
reflectance UV-Vis spectra of powders were registered 
on Lambda 35 UV-Vis spectrometer (Labsphere RSA-
PE-20 diffuse reflectance and transmittance accessory, 
Perkin-Elmer Instruments). BaSO4 was used as a ref-
erence. All spectra are presented in coordinates of Ku-
belka-Munk equation. Parameters of porous structure 
(specific surface area S, total pore volume VΣ, sorption 
pore volume Vs and volume of mesopores Vme) were de-
termined from isotherms of nitrogen adsorption-
desorption obtained with the help of ASAP 2405N ana-
lyzer (“Micromeritics Instrument Corp”). 
 
2.3. Catalytic activity  
 
The testing of photocatalytic activity was carried 
out using degradation of Rhodamine B (Rh B) in aque-
ous medium (0.5·10-5 mol L-1 solution). This reaction 
was performed in glass reactor with magnetic stirrer. 
The illumination was realized using high-intensity dis-
charge Na lamp GE Lucalox (Hungary) with power 
70 W which irradiates solely in visible region. The ratio 
catalyst/dye solution was 100 mg/150 ml and 100 mg/50 
ml during visible and UV-illumination, respectively. 
The initial solution and that after dye degradation was 
analyzed spectrophotometrically at λmax  555 nm 
(Lambda 35, PerkinElmer Instruments) after centrifu-
gation of reaction mixture (10 min at 8000 rpm). The 
calculation of photodegradation rate constants Kd was 
based on the concentration change of the solution after 
establishment of adsorption/desorption equilibrium. 
The samples of silver niobate were also tested as cata-
lysts in mechanochemical degradation of Rh B in solu-
tion (0.005 g L-1). 
 
3. RESULTS AND DISCUSSION 
 
3.1 Phase composition 
 
XRD and DTA-TG data show that silver niobates do 
not formed on the stage of modification. However, cris-
tallinity of reagents is changed. Thus, UST causes 
complete amorphization of reagents. At the same time, 
crystal structure of both components is partially de-
stroyed as a result of MChT. Both results can be esti-
mated as preparation of activated precursors. Indeed, 
 V. SYDORCHUK, S. KHALAMEIDA, J. SKUBISZEWSKA-ZIĘBA PROC. NAP 2, 01PCSI12 (2013) 
 
 
01PCSI12-2 
the next calcinations of obtained precursors results in 
facilitation of interaction between components as well 
as formation of pure niobates. 
Pure silver niobate does not formed from initial 
(non-activated) mixture after its annealing at 700˚C: 
reflexes of Nb2O5 are presented on diffractogramm (Fig. 
1, curve a). 
 
 
 
Fig. 1 – XRD patterns of AgNO3+Nb2O5 mixture: initial mix-
ture after calcined at 700 C (a), after MChT in air at 850 rpm 
(b), the same after calcined at 450 C (c),  after MChT in water 
at 850 rpm and calcined at 600 C (d) 
 
For example, sonochemical precursor is X-ray amor-
phous although its calcinations at 600 C cause appear-
ance of crystalline silver niobate. However, thermal 
treatment of precursor prepared through dry milling 
leads to formation of silver niobate AgNbO3 at 450 C 
(curve c). Elevation of temperature results in improve-
ment of crystal structure of AgNbO3. Crystallite size D020 
increases from 17 to 21 nm.  On the other hand, bi-phase 
product is formed in the same conditions from precursor 
activated via milling in water. These are Ag2Nb4O11 
(prevalent phase) and Nb2O5 (curve d). Content of nio-
bate and its crystallite size also increases after calcina-
tions at higher temperature. Raman spectra of calcined 
samples additionally exhibit differences in their struc-
ture (Fig. 2, curves a and b): there are three bands at-
tributed to AgNbO3 around 214, 256, 570 cm -1 [4]. These 
peaks are absent on spectrum of sample prepared from 
milled in water precursor. The latter sample contains 
another niobate, namely Ag2Nb4O11. 
 
 
 
Fig. 2 – Raman spectra for AgNO3+Nb2O5 mixture: initial 
mixture after calcined at 450 C (a), after MChT in air and 
calcined at 600 C (b), after MChT in water and calcined at 
600 C (c) 
 
3.2 Porous structure 
 
The specific surface area and parameters of porous 
structure of prepared silver niobate can be varied when 
conditions of modification and next calcinations are 
changed. Thus, milling in water and air enables to pre-
pare sample with increased S compared to that synthe-
sized by means of conventional solid state interaction 
(Table, samples NN1-7). Thus, specific surface area of 
sample milled in water and calcined at 450 C reaches 
8 m2·g-1 while “solid state” samples has  S  4.1 m2·g-1. 
The use of high-dispersed Nb2O5 and ultrasound treat-
ment allow to obtain macro-mesoporous samples pos-
sessing high values S and Vme (samples NN8-10). 
 
3.3 Catalytic activity 
 
The samples of silver niobate prepared from mech-
anochemical and sonochemical precursors also exhibit 
higher photocatalytic activity in process of rhodamine 
B degradation under UV- and visible light. This shows 
the kinetic curves, expressed on Fig. 3, and the rate 
constant of degradation under visible irradiation, val-
ues of which are presented in column 7 of Table. Be-
sides, one can see a clear dependence between Kd and 
value of specific surface area which is characteristic for 
photocatalytic properties, as a rule [5]. Similarly, the 
rate constant of mechanocatalytic degradation of Rh B 
increases with increasing of specific surface area of 
catalyst (silver niobate). The values of Kd for this pro-
cess are higher than ones obtained for visible photo-
catalytic degradation and equal within 2.3-5.3 10-4 s-1.  
 
Table 1 – Some properties of silver niobate samples 
 
N Modification conditions S, m2·g-1 VΣ, cm3·g-1 Vs, cm3·g-1 Vme, cm3·g-1 Kd·105, s-1 
1 2 3 4 5 6 7 
1 (AgNO3+Nb2O5) TT 700ºC 4.1 0.50 0.05 0.05 0.81 
2 (Ag NO3+Nb2O5) MChT 850 rpm air 2.8 0.01 0.005 0.005 - 
3 (AgNO3+Nb2O5) MChT 850 rpm air+TT 
450ºC 
6.8 0.03 0.01 0.01 3.90 
4 (AgNO3+Nb2O5) MChT 850 rpm air+TT 
600ºC 
4.5 0.01 0.005 0.01 1.27/3
7.5* 
 SYNTHESIS AND PHOTOCATALYTIC PROPERTIES … PROC. NAP 2, 01PCSI12 (2013) 
 
 
01PCSI12-3 
1 2 3 4 5 6 7 
5 (Ag NO3+Nb2O5) MChT 850 rpm water 5.4 0.21 0.01 0.01 - 
6 (AgNO3+Nb2O5) MChT 850 rpm water+TT 
450ºC 
8.0 0.28 0.02 0.02 5.5 
7 (AgNO3+Nb2O5) MChT 850 rpm water+TT 
600ºC 
6.7 0.20 0.005 0.01 2.39 
8 (Ag NO3+Nb2O5) UST 2 h 156 0.93 0.26 0.25 6.32 
9 (Ag NO3+Nb2O5) UST 2 h+TT 450ºC  93 0.62 0.18 0.19 3.16 
10 (Ag NO3+Nb2O5) UST 2 h+TT 600ºC 45 0.51 0.14 0.14 2.03 
*- under UV-irradiation 
 
 
 
Fig. 3 – Kinetic curves of photocatalytic Rh B degradation in 
the presence of  AgNO3+Nb2O5 after MChT in air and calcined 
at: 600 °C (a) and 450 °C (b) under visible irradiation, 600 °C 
under UV-irradiation (c) 
 
Noteworthy that shift of band at 555 nm (about 
10 nm) towards shorter wavelengths (namely, to 
545 nm) is observed on spectra of Rh B solution after 
the first 15 min of UV- and visible photocatalytic deg-
radation (for example, Fig. 4).  
 
 
 
Fig. 4 – UV-Vis spectral changes of Rhodamin B aqueous solution 
in the presence of AgNbO3 after MChT at 850 rpm in  water and 
calcined at 450 C (sample N6) after visible irradiation 
This corresponds to formation of N,N-diethyl-N’-
ethyl-rhodamine 110 (intermediate) as a result of 
deethylation of Rh B [6]. The cleavage of chromoforic 
ring obviously takes place later which leads to reduc-
tion of band 545 nm intensity. The further shift to 
535 nm is observed after 180-240 min. On the other 
hand, such shift does not revealed in spectra of Rh B 
solutions after mechanochemical degradation for the 
same time. Meanwhile, only decrease of band at 
555 nm occurs. 
 
4. CONCLUSION 
 
Mechano- and sonochemical activation allow to low-
er (compared to conventional solid state reaction) tem-
perature of interaction of AgNO3 and Nb2O5 with for-
mation of silver niobates. Milling in air promotes for-
mation of AgNbO3 while milling in water results in 
appearance of Ag2Nb4O11 phase. The formed niobates 
possess higher specific surface area and photocatalytic 
and mechanocatalytic activity in process of rhodamine 
B degradation, as a result.  
 
AKNOWLEDGEMENTS. 
 
This work was supported by the State Science 
Technology Program “Nanotechnology and nano-
materials” Project No 6.22.1.9. 
 
 
 
 
 
 
 
 
 
 
 
 
REFERENCES 
 
1. H. Shu, J. Xie, H. Xu, H. Li, Z. Gua, G. Sun, Y. Xu, 
J. Alloys Comp. 496, 633 (2010). 
2. A. Kudo, Int. J. Hydrogen Energy 31, 197 (2006). 
3. G. Li, Y. Bai, X. Liu, W.F. Zhang, J. Phys. D: Appl. Phys. 
42, 253503 (2009). 
4. D.S. Stone, J. Migas, A. Martini, et al., Surf. Coat. Tech-
nol. 206, 4316 (2012). 
5. L.P. Thompson, J.T. Yates, Chem. Rev. 106, 4428 (2006). 
6. F. Chen, J. Zhao, H. Hidaka, Int. J. Photoenergy 5, 209 
(2003). 
 
 


Synthesis and Photocatalytic Properties of Silver Niobate

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 2 No 1, 01PCSI12 (3pp) (2013)   2304-1862/2013/2(1)01PCSI12(3) 01PCSI12-1  2013 Sumy State University Synthesis and Photocatalytic Properties of Silver Niobate  V. Sydorchuk1, S. Khalameida1, J. Skubiszewska-Zięba2, R. Leboda2, V. Starchevskii 3, V. Zazhigalov1, O. Zakutevskii1  1 Institute for Sorption and Problems of Endoecology National Academy of Science of Ukraine, 13, Naumov Str., 03164, Kyiv, Ukraine 2 Faculty of Chemistry, Maria Curie-Sklodowska, 3, pl. Marie Curie-Sklodowska, 20031, Lublin, Poland 3 Department of General Chemistry, Lviv Polytechnic National University, 12,  Bandera Str., 79013, Lviv, Ukraine   (Received 30 May 2013; published online 1 September 2013)  The interaction between silver nitrate and niobium pentoxide has been studied under conventional thermal treatment (TT) as well as mechanochemical and sonochemical treatment (MChT and UST, respec-tively). The products of reaction have been investigated using XRD, DTA-TG, Raman spectroscopy, adsorp-tion of nitrogen. MChT and UST promote lowering the temperature of silver niobate (SN) formation. The formed SN possesses higher specific surface area and photocatalytic activity.   Keywords: Silver Niobate,  Milling, Sonochemichal Treatment, Photocatalytic Activity.   PACS number: 42.70.Qs   1. INTRODUCTION  The development of photocatalysts with visible-light response has been studied extensively from the view-point of the utilization of solar light energy including for degradation of pollutants in air and water. Such ferroelectric material as silver niobate AgNbO3 pos-sessing the perovskite structure is a potential photo-catalyst [1, 2]. The AgNbO3 samples were usually pre-pared using a solid-state reaction method by mixing powders of Ag2O and Nb2O5 in nonstoichiometric ratio, followed by a pre-heat treatment at 800 C for 4 h and then calcination at 970 C for 7 h in air [3]. In this work, we studied the influence of preliminary sono- and mechanochemical activation of reaction mixture Ag-NO3+Nb2O5 on structure and catalytic properties of AgNbO3.  2. EXPERIMENTAL PROCEDURE  2.1 Silver niobate synthesis  Silver nitrate and niobium pentaoxide with differ-ent specific surface area (2 and 355 m2·g-1) were used as initial reagents. These mixtures were subjected to ul-trasound and mechanochemical treatment (UST and MChT, respectively) in water and air. Activated prod-ucts (precursors) were additionally calcined at 450 and 600 C.  2.2 Physical-chemical characterization  The phase composition was studied by means of X-ray powder diffraction (XRD) using Philips PW 1830 diffractometer with CuKα-radiation. The primary crys-tallites size Dhkl was calculated using the broadening of the most intensive lines according to Sherrer’s equa-tion. Curves of DTA and TG were recorded using Deri-vatograph-C apparatus (F.Paulik, J.Paulik, L.Erdey) in the range of temperature 20-600 C at the heating rate 10 /min. Initial mass of sample was 200 mg. Diffuse reflectance UV-Vis spectra of powders were registered on Lambda 35 UV-Vis spectrometer (Labsphere RSA-PE-20 diffuse reflectance and transmittance accessory, Perkin-Elmer Instruments). BaSO4 was used as a ref-erence. All spectra are presented in coordinates of Ku-belka-Munk equation. Parameters of porous structure (specific surface area S, total pore volume VΣ, sorption pore volume Vs and volume of mesopores Vme) were de-termined from isotherms of nitrogen adsorption-desorption obtained with the help of ASAP 2405N ana-lyzer (“Micromeritics Instrument Corp”).  2.3. Catalytic activity   The testing of photocatalytic activity was carried out using degradation of Rhodamine B (Rh B) in aque-ous medium (0.5·10-5 mol L-1 solution). This reaction was performed in glass reactor with magnetic stirrer. The illumination was realized using high-intensity dis-charge Na lamp GE Lucalox (Hungary) with power 70 W which irradiates solely in visible region. The ratio catalyst/dye solution was 100 mg/150 ml and 100 mg/50 ml during visible and UV-illumination, respectively. The initial solution and that after dye degradation was analyzed spectrophotometrically at λmax  555 nm (Lambda 35, PerkinElmer Instruments) after centrifu-gation of reaction mixture (10 min at 8000 rpm). The calculation of photodegradation rate constants Kd was based on the concentration change of the solution after establishment of adsorption/desorption equilibrium. The samples of silver niobate were also tested as cata-lysts in mechanochemical degradation of Rh B in solu-tion (0.005 g L-1).  3. RESULTS AND DISCUSSION  3.1 Phase composition  XRD and DTA-TG data show that silver niobates do not formed on the stage of modification. However, cris-tallinity of reagents is changed. Thus, UST causes complete amorphization of reagents. At the same time, crystal structure of both components is partially de-stroyed as a result of MChT. Both results can be esti-mated as preparation of activated precursors. Indeed,  V. SYDORCHUK, S. KHALAMEIDA, J. SKUBISZEWSKA-ZIĘBA PROC. NAP 2, 01PCSI12 (2013)   01PCSI12-2 the next calcinations of obtained precursors results in facilitation of interaction between components as well as formation of pure niobates. Pure silver niobate does not formed from initial (non-activated) mixture after its annealing at 700˚C: reflexes of Nb2O5 are presented on diffractogramm (Fig. 1, curve a).    Fig. 1 – XRD patterns of AgNO3+Nb2O5 mixture: initial mix-ture after calcined at 700 C (a), after MChT in air at 850 rpm (b), the same after calcined at 450 C (c),  after MChT in water at 850 rpm and calcined at 600 C (d)  For example, sonochemical precursor is X-ray amor-phous although its calcinations at 600 C cause appear-ance of crystalline silver niobate. However, thermal treatment of precursor prepared through dry milling leads to formation of silver niobate AgNbO3 at 450 C (curve c). Elevation of temperature results in improve-ment of crystal structure of AgNbO3. Crystallite size D020 increases from 17 to 21 nm.  On the other hand, bi-phase product is formed in the same conditions from precursor activated via milling in water. These are Ag2Nb4O11 (prevalent phase) and Nb2O5 (curve d). Content of nio-bate and its crystallite size also increases after calcina-tions at higher temperature. Raman spectra of calcined samples additionally exhibit differences in their struc-ture (Fig. 2, curves a and b): there are three bands at-tributed to AgNbO3 around 214, 256, 570 cm -1 [4]. These peaks are absent on spectrum of sample prepared from milled in water precursor. The latter sample contains another niobate, namely Ag2Nb4O11.    Fig. 2 – Raman spectra for AgNO3+Nb2O5 mixture: initial mixture after calcined at 450 C (a), after MChT in air and calcined at 600 C (b), after MChT in water and calcined at 600 C (c)  3.2 Porous structure  The specific surface area and parameters of porous structure of prepared silver niobate can be varied when conditions of modification and next calcinations are changed. Thus, milling in water and air enables to pre-pare sample with increased S compared to that synthe-sized by means of conventional solid state interaction (Table, samples NN1-7). Thus, specific surface area of sample milled in water and calcined at 450 C reaches 8 m2·g-1 while “solid state” samples has  S  4.1 m2·g-1. The use of high-dispersed Nb2O5 and ultrasound treat-ment allow to obtain macro-mesoporous samples pos-sessing high values S and Vme (samples NN8-10).  3.3 Catalytic activity  The samples of silver niobate prepared from mech-anochemical and sonochemical precursors also exhibit higher photocatalytic activity in process of rhodamine B degradation under UV- and visible light. This shows the kinetic curves, expressed on Fig. 3, and the rate constant of degradation under visible irradiation, val-ues of which are presented in column 7 of Table. Be-sides, one can see a clear dependence between Kd and value of specific surface area which is characteristic for photocatalytic properties, as a rule [5]. Similarly, the rate constant of mechanocatalytic degradation of Rh B increases with increasing of specific surface area of catalyst (silver niobate). The values of Kd for this pro-cess are higher than ones obtained for visible photo-catalytic degradation and equal within 2.3-5.3 10-4 s-1.   Table 1 – Some properties of silver niobate samples  N Modification conditions S, m2·g-1 VΣ, cm3·g-1 Vs, cm3·g-1 Vme, cm3·g-1 Kd·105, s-1 1 2 3 4 5 6 7 1 (AgNO3+Nb2O5) TT 700ºC 4.1 0.50 0.05 0.05 0.81 2 (Ag NO3+Nb2O5) MChT 850 rpm air 2.8 0.01 0.005 0.005 - 3 (AgNO3+Nb2O5) MChT 850 rpm air+TT 450ºC 6.8 0.03 0.01 0.01 3.90 4 (AgNO3+Nb2O5) MChT 850 rpm air+TT 600ºC 4.5 0.01 0.005 0.01 1.27/37.5*  SYNTHESIS AND PHOTOCATALYTIC PROPERTIES … PROC. NAP 2, 01PCSI12 (2013)   01PCSI12-3 1 2 3 4 5 6 7 5 (Ag NO3+Nb2O5) MChT 850 rpm water 5.4 0.21 0.01 0.01 - 6 (AgNO3+Nb2O5) MChT 850 rpm water+TT 450ºC 8.0 0.28 0.02 0.02 5.5 7 (AgNO3+Nb2O5) MChT 850 rpm water+TT 600ºC 6.7 0.20 0.005 0.01 2.39 8 (Ag NO3+Nb2O5) UST 2 h 156 0.93 0.26 0.25 6.32 9 (Ag NO3+Nb2O5) UST 2 h+TT 450ºC  93 0.62 0.18 0.19 3.16 10 (Ag NO3+Nb2O5) UST 2 h+TT 600ºC 45 0.51 0.14 0.14 2.03 *- under UV-irradiation    Fig. 3 – Kinetic curves of photocatalytic Rh B degradation in the presence of  AgNO3+Nb2O5 after MChT in air and calcined at: 600 °C (a) and 450 °C (b) under visible irradiation, 600 °C under UV-irradiation (c)  Noteworthy that shift of band at 555 nm (about 10 nm) towards shorter wavelengths (namely, to 545 nm) is observed on spectra of Rh B solution after the first 15 min of UV- and visible photocatalytic deg-radation (for example, Fig. 4).     Fig. 4 – UV-Vis spectral changes of Rhodamin B aqueous solution in the presence of AgNbO3 after MChT at 850 rpm in  water and calcined at 450 C (sample N6) after visible irradiation This corresponds to formation of N,N-diethyl-N’-ethyl-rhodamine 110 (intermediate) as a result of deethylation of Rh B [6]. The cleavage of chromoforic ring obviously takes place later which leads to reduc-tion of band 545 nm intensity. The further shift to 535 nm is observed after 180-240 min. On the other hand, such shift does not revealed in spectra of Rh B solutions after mechanochemical degradation for the same time. Meanwhile, only decrease of band at 555 nm occurs.  4. CONCLUSION  Mechano- and sonochemical activation allow to low-er (compared to conventional solid state reaction) tem-perature of interaction of AgNO3 and Nb2O5 with for-mation of silver niobates. Milling in air promotes for-mation of AgNbO3 while milling in water results in appearance of Ag2Nb4O11 phase. The formed niobates possess higher specific surface area and photocatalytic and mechanocatalytic activity in process of rhodamine B degradation, as a result.   AKNOWLEDGEMENTS.  This work was supported by the State Science Technology Program “Nanotechnology and nano-materials” Project No 6.22.1.9.             REFERENCES  1. H. Shu, J. Xie, H. Xu, H. Li, Z. Gua, G. Sun, Y. Xu, J. Alloys Comp. 496, 633 (2010). 2. A. Kudo, Int. J. Hydrogen Energy 31, 197 (2006). 3. G. Li, Y. Bai, X. Liu, W.F. Zhang, J. Phys. D: Appl. Phys. 42, 253503 (2009). 4. D.S. Stone, J. Migas, A. Martini, et al., Surf. Coat. Tech-nol. 206, 4316 (2012). 5. L.P. Thompson, J.T. Yates, Chem. Rev. 106, 4428 (2006). 6. F. Chen, J. Zhao, H. Hidaka, Int. J. Photoenergy 5, 209 (2003).   

The interaction between silver nitrate and niobium pentoxide has been studied under conventional thermal treatment (TT) as well as mechanochemical and sonochemical treatment (MChT and UST, respec-tively). The products of reaction have been investigated using XRD, DTA-TG, Raman spectroscopy, adsorp-tion of nitrogen. MChT and UST promote lowering the temperature of silver niobate (SN) formation. The formed SN possesses higher specific surface area and photocatalytic activity

Synthesis and Photocatalytic Properties of Silver Niobate

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