Thermal, Mechanical, and Chemical Properties of Sintered Xenotime‐Type RPO4 (R = Y, Er, Yb, or Lu)

Xenotime‐type RPO 4 (R = Y, Er, Yb, or Lu) powder was dry‐pressed into disks and bars. The disks and bars could be sintered to a relative density of greaterthan equal to98% in air without cracking at 1300° (R = Yb or Lu) or 1500°C (R = Y or Er), depending on the grain size. The linear thermal expansion coefficient (at 1000°C), thermal conductivity (at 20°C), and bending strength (at 20°C) of the xenotime‐type RPO 4 ceramics were 6.2 10 ‐6 /°C, 12.02 W(mK) ‐1 , and 95 ± 29 MPa for R = Y; 6.0 10 ‐6 /°C, 12.01 W(mK) ‐1 , and 100 ± 21 MPa for R = Er; 6.0 10 ‐6 /°C, 11.71 W(mK) ‐1 , and 135 ± 34 MPa for R = Yb; and 6.2 10 ‐6 /°C, 11.97 W(mK) ‐1 , and 155 ± 25 MPa for R = Lu. The xenotime‐type RPO 4 ceramics did not react with SiO 2 , TiO 2 , Al 2 O 3 , ZrO 2 , or ZrSiO 4 , even at 1600°C for 3 h in air, and were stable in aqueous solutions of HCl, H 2 SO 4 , HNO 3 , NaOH, and NH 4 OH at 20°C.