Yttrium zirconium phosphate (YPO₄·Zr₃(PO₄)₄, YZP) is an inorganic material obtained by modifying zirconium phosphate with the rare-earth element yttrium. It has a tetragonal crystal system with a high melting point, high hardness, a low thermal expansion coefficient and excellent chemical inertness and thermal stability. It is used in high-performance ceramics, catalyst carriers (surface yttrium sites enhance solid acidity for esterification and alkylation, recommended addition 1–10 wt%), nuclear-waste immobilisation (good radiation stability, recommended 0.5%–5%), optical materials (laser and fluorescent materials), gas sensors (sensitive to CO and NOₓ) and lithium/sodium-ion batteries (stabilising the crystal structure, suppressing phase transitions and extending cycle life).
