Preparation, thermal stability and magnetic properties of new AgY1−xGdx(WO4)2 ceramic materials

Some optical and transport properties of a new subclass of ceramic tungstates and molybdates

“…show polymorphism and they crystallize in two polymorphs of the monoclinic (α-polymorph, the space group C 2 /m) and the tetragonal structure, similar to that of scheelite-type (β-polymorph, space group I 4 ), symmetries [18,19].…”

“…SEM images showed that the grain size of α-AgY 1-x Gd x (WO 4 ) 2 varied in the range from ~1 to ~5 µm [19].…”

“…Polycrystalline samples of α-AgY 1-x (Gd,Nd) x (WO 4 ) 2 with x = 0, 0.005, 0.01, 0.025, 0.05, 0.1, 0.2, and 1 were prepared by a solid state reaction method using Ag 2 WO 4 and RE 2 (WO 4 ) 3 (RE = Y, Nd, and Gd); the starting reactants and the thermal conditions are described in [19]. SEM images showed that the grain size of α-AgY 1-x Gd x (WO 4 ) 2 varied in the range from ~1 to ~5 µm [19].…”

Synthesis, structure, and thermal stability of new scheelite-type Pb1−3x□xPr2x(MoO4)1−3x(WO4)3x ceramic materials

“…The first one started at 1037°C is connected with a phase transformation of a monoclinic a-Pr 2 (WO 4 ) 3 (space group C2/c) to a high-temperature polymorph (b) with a orthorhombic symmetry (space group Pnca, a structure of Sc 2 (MoO 4 ) 3 -type) [51,52]. A similar polymorphic change is observed in other rare-earth metal tungstates, e.g., for Gd 2 (WO 4 ) 3 [38]. Praseodymium tungstate melts congruently in air at 1112°C (the second endothermic effect on DTA curve of this compound recorded during controlled heating).…”

“…Lead molybdate was prepared by heating PbO with MoO 3 (both with the purity 99.95 %, Alfa Aesar) mixed in an equimolar ratio, and in the following thermal conditions: 550°C (6 h), 600°C (6 h), 700°C (6 h), 800°C (12 h), 900°C (12 h), and 950°C (12 h). Praseodymium tungstate was obtained using a solid-state reaction method [37][38][39][40][41][42][43][44][45] and Pr 6 O 11 with WO 3 (both with the purity 99.95 %, Alfa Aesar) mixed in the 1:9 molar ratio according to the procedure used by us in a synthesis of other rare-earth tungstates, and under thermal conditions reported earlier [25][26][27][28][37][38][39]. Mixtures of starting reactants with Pr 2 (WO 4 ) 3 content changing from 0.50 to 50.00 mol% were homogenized in an agate mortar.…”