New cadmium and rare-earth metal molybdates with scheelite-type structure

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

“…The new Cd 1-3x Gd 2x x MoO 4 molybdates (x = 0.0005, 0.0098, 0.0238, 0.0455, 0.0839, 0.1667, 0.2000, and 0.2222) were successfully synthesized via a high-temperature annealing of CdMoO 4 /Gd 2 (MoO 4 ) 3 mixtures in which the content of gadolinium molybdate did not exceed 50 mol% [13,14,22,23]. SEM images showed that the grain size of new molybdate materials varied in the range from ~2 to ~30 µm [14].…”

“…Molybdates and tungstates doped with Nd 3+ , Dy 3+ , Ho 3+ , Er 3+ ,Tm 3+ or Yb 3+ are used as ultra-fast diode pumped solid state lasers while doped with europium trivalent ions are used in light emitting diodes (LEDs) [1][2][3][4][5][6][7][8]. For many years we have conducted optical studies of new RE 3+ -doped molybdates and tungstates having two different types of structures (scheelite or wolframite-type) [9][10][11][12][13][14][15][16] [9,10]. Very strong red emission was observed in new tetragonal scheelite-type Cd 0.25 Gd 0.50 0.25 WO 4 ( denotes cationic vacancies) that is the host in which europium trivalent ions can easily substitute Gd 3+ ones and Eu 3+ ions occupy only low symmetry site of a certain type [11].…”

“…However, a special group of new materials are Cd 1-3x RE 2x x MoO 4 solid solutions, with the value of x strongly dependent on the radius of the rare earth ion [13][14][15][16]. The substitution of divalent Cd 2+ ions by trivalent RE 3+ ones leads to formation of cationic vacancies in the tetragonal scheelite-type CdMoO 4 framework (the space group I4 1 /a) as a result of the charge compensation: 3Cd 2+ → 2RE 3+ + vacancy ( ).…”

EPR properties of some new cadmium and rare-earth molybdates, molybdato-tungstates and their solid solutions

“…We also investigated the mutual reactivity in the solid state of cadmium molybdate (CdMoO 4 , the scheelite-type structure) with some rare-earth metal molybdates of the formula RE 2 (MoO 4 ) 3 or tungstates of the formula RE 2 (WO 4 ) 3 , where RE = Pr, Nd, Sm-Dy [19,20]. We synthesized new solid solutions: Cd 1−3x RE 2x x MoO 4 and Cd 1−3x RE 2x x (MoO 4 ) 1−3x (WO 4 ) 3x (where the symbol means vacancies in a cation sublattice) for 0 < x ≤ 0.25, according to the following solid-state reactions [19,20]: [19,20]. Their lattice constants linearly decrease as increase an atomic number of RE 3+ ion [19,20].…”

“…We synthesized new solid solutions: Cd 1−3x RE 2x x MoO 4 and Cd 1−3x RE 2x x (MoO 4 ) 1−3x (WO 4 ) 3x (where the symbol means vacancies in a cation sublattice) for 0 < x ≤ 0.25, according to the following solid-state reactions [19,20]: [19,20]. Their lattice constants linearly decrease as increase an atomic number of RE 3+ ion [19,20]. According to the Vegard law, the unit cell parameters of new solid solutions also linearly decrease as the CdMoO 4 content in CdMoO 4 /RE 2 (MoO 4 ) 3 as well as in CdMoO 4 /RE 2 (WO 4 ) 3 initial reaction mixtures increases [19,20].…”