Yttrium(III) phosphate

Yttrium phosphate can be obtained by reacting yttrium chloride and sodium phosphate, or by reacting yttrium nitrate and diammonium hydrogen phosphate in solution:^[2]

${\displaystyle \mathrm {YCl_{3}+(NH_{4})_{3}PO_{4}\longrightarrow YPO_{4}\downarrow +3\ NH_{4}Cl} }$

${\displaystyle \mathrm {Y(NO_{3})_{3}+(NH_{4})_{2}HPO_{4}\longrightarrow YPO_{4}\downarrow \ +2\ NH_{4}NO_{3}+HNO_{3}} }$

Yttrium phosphate can also be prepared by the reaction of yttrium(III) oxide and diammonium hydrogen phosphate:^[4]

${\displaystyle \mathrm {Y_{2}O_{3}+2\ (NH_{4})_{2}HPO_{4}\longrightarrow YPO_{4}+2\ NH_{3}+3\ H_{2}O} }$

Yttrium chloride and phosphoric acid are mixed at 35~40°C, and then ammonia solution is added dropwise to react:^[5]

${\displaystyle \mathrm {YCl_{3}+H_{3}PO_{4}+3NH_{3}\cdot H_{2}O\ {\xrightarrow {35-40^{o}C}}\ YPO_{4}+3NH_{4}Cl+3H_{2}O} }$

Yttrium phosphate belongs to the tetragonal crystal system, and the unit cell parameters are a=0.68832 nm, c=0.60208 nm. It can exist as a monohydrate, dihydrate or the anhydrous form. The dihydrate belongs to the monoclinic crystal system, the space group is B 2/b, and the unit cell parameters are a=0.648 nm, b=1.512 nm, c=0.628 nm, β=129.4°, Z=4.^[6]

Yttrium phosphate reacts with concentrated alkali to form yttrium hydroxide.^[7]

Yttrium phosphate is used as a catalyst and is a potential containment material for nuclear waste.^[2] Ce³⁺-doped yttrium phosphate shows luminescence in the UV range and can be used for tanning lamps.^[8][9] Double-doped materials such as Ce³⁺-Tb³⁺ have also been reported.