Nanoscale physics

Anomalies of Pb2MoO5 permittivity induced by UV irradiation 
I. Volnyanskaya1, M. Trubitsyn2, D. Bondar2, M. Buryi3, V. Laguta3, 
D. Volnyanskii4 
1 Prydniprovska state academy of building and architecture, 
vul. Chernyshevs’kogo 24 a, Dnipro, 49000, Ukraine. 
2 Oles Honchar Dnipro National University, 
prosp. Gagarina 72, Dnipro, 49010, Ukraine. 
E-mail: trubitsyn_m@ua.fm
3 Institute of Physics, CAS, The Czech Academy of Sciences, 
Cukrovarnicka 10/112, 162 00 Prague, Czechia.
4 Dnipro National University of Railway Transport named after academician 
V. Lazaryan, vul. Akademika Lazaryana, 2, Dnipro, 49010, Ukraine.

The dielectric properties of double lead molybdate Pb2MoO5 single crystal, exposed to UV light radiation (290 K), were studied in AC field (f=1 kHz) [1]. Appearance of permittivity  maximum near 530 K was detected after UV irradiation. The magnitude of the  peak increased for longer times of UV light exposure. Heating up to 700 K resulted in thermal dissociation of the dipole complexes, induced by UV light and contributing to  peak. 
It is supposed that the observed anomaly of  is determined by dielectric response of nanometer sized molybdenum-oxygen complexes which can be regular or distorted by substitutional impurities or lead vacancies in the immediate neighborhood. According to [2] (MoO3)- centers arise when photoelectrons are trapped by molybdenum ions with oxygen vacancy VO in the nearest surroundings. It is expected that (MoO3)- centers can cause photochromism, which worsens optical quality of Pb2MoO5 crystals. Undesirable photochromic effect can be eliminated by heterovalent doping with transition groups ions.

1.	Volnyanskaya I.P., Trubitsyn M.P., Volnyanskii D.M., Bondar D.S., Shvets T.V. Dielectric properties of the Pb2MoO5 crystals irradiated with UV light // Vìsnik Dnìpropetrovs’kogo unìversitetu. Serìâ Fìzika, radìoelektronika. - 2017.- 25, N 24.-P. 79-83.
2.	Buryi M., Laguta V., Fasoli M., Moretti F., Trubitsyn M., Volnianskii M., Vedda A., Nikl M. Electron self-trapped at molybdenum complex in lead molybdate: An EPR and TSL comparative study // J of Luminescence. -2005. -192.-P. 767-774.