Materials based on compounds with common formulae REAO₄ (RЕ – rare earth element,  A – element of the 5th group of Periodic table) are widely applied in optics, X-ray visualization and proposed for usage as scintillators for registration of X- and γ-rays [1, 2]. Rare earth orthotantalates due to high density from 7,8 g/cm3 for  LaTaO₄ up to 9,75 g/cm3 for LuTaO₄ can be considered as promising scintillators for high-energy physics. During recent 5 years materials based on yttrium tantalate-niobates with common formulae Y(Ta_1-xNb_x)O₄ attracted great interest [3, 4] from both scientific and technical points of view.

In the present work, methods of obtaining, luminescent and scintillation properties of compounds with common formulae REAO₄ (A=V, Ta and Nb) were explored. Optimal regimes of raw material solid-state synthesis were determined; content of the main phase after solid-state synthesis was up to 99%. Ceramic samples of both undoped orthotantalates (RETaO₄)  and tantalate-niobates (RE(Ta_1-xNb_x)O₄) and doped with familiar dopant (Eu, Pr и Ce) for scintillation materials were obtained. Single crystals of undoped orthovanadates (REVO₄) were grown by Czochralski technique. Optimal regimes of after-growth annealing for elimination of oxygen vacancies forming during the crystal growth in inert atmosphere, were determined.

YVO₄ and GdVO₄ single crystals demonstrate light yield up to 11500 ph/MeV, energy resolution about 16 % at 662 KeV, and microsecond decay after X- and γ -radiation. Light yield increases by 3 – 5 times at lowering the temperatures down to 77 K.

Among orthotantalates, the biggest light yield is observed with YTaO₄ and GdTaO₄ (110 % and 43 % compared to BGO). Significant light yield is observed for Eu- and Pr- doped samples as well (for example, for GdTaO₄:Eu light yield is 136 % compared to BGO). Orthotantalates demonstrate faster luminescence with decay times around 300 - 1000 ns.

With modifying of cation composition in yttrium and gadolinium tantalate-niobate samples  luminescent and scintillation characteristics of material significantly change. Light yield in some mixed compositions rises by up to 2 times compared to their constitutents. Brightest luminescence was observed for Eu-doped samples.

1. Patent WO 2008/094184 A3, publ. 07.08.2008.

2. O.V. Voloshina, V.N. Baumer, et al.,NIM A, 664 (2012) 299 – 303.

3. E.-J.Popovici, M. Nazarov, et al., Physics Procedia 2 (2009) 185–190.

4. I.D. Arellano, M.V.Nazarov, et al., J. of Lumin., 132 (2012) 2479–2483.

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