Influence of initial charge composition and growth/annealing atmospheres on the structural parameters of Czochralski-grown (NaxGd1−x)MoO4 crystals

The composition of microparts of sodium-gadolinium molybdate crystals, grown by the Czochralski method in different atmospheres from stoichiometric ((Na0.5Gd0.5)MoO4; group I) and nonstoichiometric ((Na2/7Gd4/71/7)MoO4 (II.1) and (Na6/15Gd8/151/15)MoO4 (II.2); group II) initial charge compositions (where = vacancies), was refined by X-ray diffraction analysis. All the crystals under investigation were found to crystallize in the space group I41/a without any signs of structural modulation and the refined crystal compositions were different from the initial charge compositions. Crystals from group I had a gadolinium excess and sodium deficiency without vacancies in the dodecahedral site. Vacancies were found in the Mo and O sites of the structure of the dark-gray micropart of the crystal grown in an Ar atmosphere, with the composition of the near-colorless micropart of the same crystal being close to stoichiometry. Microparts of the crystals from group II contain vacancies in both cation sites in (Na0.348(8)Gd0.5280.124)(Mo6+0.996(3)0.004)O4 (II.1) and in the dodecahedral and oxygen sites in (Na0.300(8)Gd0.5760.124)Mo6+(O3.880(10)0.120) (II.2). It was revealed that an additional annealing in air of the crystals grown in a slightly oxidizing atmosphere reduces the oxygen vacancies content. The possibility of growing crystals with an ordered structure depending on the ratio of the formula coefficients of components in the dodecahedral site of scheelite structure is thus discussed herein.

[1]  A. Cousson,et al.  Structural investigation of Pb(Mo@@ xW1-@@ x)O4 solid solutions via X-ray and neutron diffraction , 2016 .

[2]  A. Cousson,et al.  Influence of growth conditions on structural parameters of scheelite PbTO4 (T = Mo, W) crystals , 2016 .

[3]  N. Bolotina,et al.  Structural perfection of (Na0.5Gd0.5)MoO4:Yb laser crystals , 2015 .

[4]  Q. Jing,et al.  Effect of the cation size on the framework structures of magnesium tungstate, A4Mg(WO4)3 (A = Na, K), R2Mg2(WO4)3 (R = Rb, Cs). , 2015, Dalton transactions.

[5]  A. Cousson,et al.  Influence of the dopant type on point defects in PbMoO4 crystals , 2014, Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques.

[6]  P. Ryabochkina,et al.  Spectroscopic properties of Nd3+ doped NaLa0.5Gd0.5(WO4)2 crystals , 2013 .

[7]  O. Zaharko,et al.  Colors of mixed-substituted double molybdate single crystals having scheelite structure , 2012, Russian Journal of Inorganic Chemistry.

[8]  O. Lebedev,et al.  Na(2/7)Gd(4/7)MoO4: a modulated scheelite-type structure and conductivity properties. , 2012, Inorganic chemistry.

[9]  U. Griebner,et al.  Comparative study of crystallographic, spectroscopic, and laser properties of Tm 3 + in Na T (WO 4 ) 2 ( T = La, Gd, Y, and Lu) disordered single crystals , 2011 .

[10]  Lizhen Zhang,et al.  Growth and spectroscopic properties of Nd3+-doped Na2Gd4(MoO4)7 crystal , 2011 .

[11]  O. Antipov,et al.  Tunable quasi-cw two-micron lasing in diode-pumped crystals of mixed Tm3+-doped sodium — lanthanum — gadolinium molybdates and tungstates , 2010 .

[12]  V. Rybakov,et al.  Symmetry of (Na0.5R0.5)MO4 crystals (R = Gd, La; M = W, Mo) , 2010 .

[13]  A. Cousson,et al.  Composition, structural parameters, and color of langatate , 2010 .

[14]  W. Sibbett,et al.  Continuous-wave laser operation of Tm and Hoco-doped NaY(WO(4))(2) and NaLu(WO(4))(2) crystals. , 2010, Optics express.

[15]  A. Popov,et al.  Growth, refined structural and spectroscopic characteristics of Tm3+-doped NaGd(WO4)2 single crystals , 2009 .

[16]  V. Rybakov,et al.  Structural features of phases (Na0.5R0.5)MO4 and (Na0.5R0.5)MO4:R′ (R = Gd, La; R′ = Er, Tm, Yb; M = W, Mo) of the scheelite family , 2009 .

[17]  C. Zaldo,et al.  Double Tungstate and Molybdate Crystals for Laser and Nonlinear Optical Applications , 2009 .

[18]  G. Sheldrick.  A short history of SHELX. , 2008, Acta crystallographica. Section A, Foundations of crystallography.

[19]  Valentin Petrov,et al.  Structural, spectroscopic, and tunable laser properties of Yb3+-doped NaGd(WO4)2 , 2006 .

[20]  A. Popov,et al.  Growth and spectroscopic investigations of Yb3+-doped NaGd(MoO4)2 and NaLa(MoO4)2—new promising laser crystals , 2006 .

[21]  V. A. Romanyuk,et al.  Longitudinally diode-pumped 1.06-{mu}m Nd{sup 3+}:NaLa(MoO{sub 4}){sub 2} laser without pump-wavelength stabilisation , 2006 .

[22]  C. Zaldo,et al.  The optical spectroscopy of lanthanides R3+ in ABi(XO4)2 (A = Li, Na; X = Mo, W) and LiYb(MoO4)2 multifunctional single crystals: Relationship with the structural local disorder , 2005 .

[23]  V. Rybakov,et al.  Growth and structural X-ray investigations of scheelite-like single crystals Er, Ce:NaLa(MoO4)2 and Yb:NaGd(WO4)2 , 2005 .

[24]  B. A. Smirnov,et al.  X-ray Diffraction Study of the Structure and Defect System of Yb-Activated (Na0.5Gd0.5)WO4 Crystals , 2003 .

[25]  Louis J. Farrugia,et al.  WinGX suite for small-molecule single-crystal crystallography , 1999 .

[26]  R. D. Shannon.  Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides , 1976 .

[27]  D. H. Templeton,et al.  X-RAY DIFFRACTION REFINEMENT OF THE CALCIUM TUNGSTATE STRUCTURE , 1964 .