Crystal Structure, Luminescence, and Thermodynamic Properties of Pb10 – xEux(GeO4)2 + x(VO4)4 – x (x = 0.1, 0.2, 0.3) Substituted Apatites

Synthesis of Sodium-Lead Apatite Structure with the Excess and the Lack of Sodium

“…In addition to the sodium apatite phase, the parameters were thus increased. No change in the parameters was impacted by the decrease in sodium in the pure lead apatite compound [23,24].…”

Synthesis, crystal structure and high-temperature heat capacity of substituted apatites Pb-=SUB=-9-=/SUB=-R(GeO-=SUB=-4-=/SUB=-)-=SUB=-3-=/SUB=-(VO-=SUB=-4-=/SUB=-)-=SUB=-3-=/SUB=- (R=Tb, Dy, Ho)

“…Such a substitution allows both for changing the properties of the already known compounds with the apatite structure and for making new materials [16,17]. Thus, for instance, partial substitution of lead in apatite Pb 5 (GeO 4 )(VO 4 ) 2 (or Pb 10 (GeO 4 ) 2 (VO 4 ) 4 ) by rare earth elements (REE) provides compounds with the general formula Pb 10−x R x (GeO 4 ) 2+x (VO 4 ) 4−x (Rrare earth element, x takes on values from 0 to 3) [13,[18][19][20][21][22][23][24][25], and by bismuth -Pb 10−x Bi x (GeO 4 ) 2+x (VO 4 ) 4−x [26]. It should be noted that the properties of apatites Pb 10−x R x (GeO 4 ) 2+x (VO 4 ) 4−x have been poorly studied, while the available data mainly pertains to epy studies of their crystal structure.…”

“…We have obtained the heat capacity data only for the apatites of this class which contain La [19,20,22,25], Pr [23,25], Nd [21,25], Eu [24], Sm [25]. The available published data about thermodynamic properties pertains to other compounds with the apatite structure (fluor-, chlor-and hydroxyapatites) [27,28].…”