Physical Properties of La1−xEuxPO4,0 ≤ x ≤ 1, Monazite‐Type Ceramics

Synthetic La1−xEuxPO4 monazite-type ceramics with 0 ≤ x ≤ 1 have been characterized by ultrasound techniques, dilatometry, and micro-calorimetry. The coefficients of thermal expansion and the elastic properties are, to a good approximation, linearly dependent on the europium concentration. Elastic stiffness coefficients range from 182(1) to 202(1) GPa for c11 and from 53.8(7) to 61.1(4) GPa for c44. They are strongly dependent on the density of the sample. The coefficient of thermal expansion at 673 K is 8.4(3)  × 10−6 K−1 for LaPO4 and 9.9(3)  × 10−6 K−1 for EuPO4, respectively. The heat capacities at ambient temperature are between 101.6(8) J·(mol·K)−1 for LaPO4 and 110.1(8) J·(mol·K)−1 for EuPO4. The difference between the heat capacity of LaPO4 and the Eu-containing solid solutions is dominated by electronic transitions of the 4f-electrons at temperatures above 75 K.