Thermal and elastic properties of silicate oxyapatite crystals

Abstract

The elastic constants, thermal expansion, thermal conductivity, and heat capacity are reported for a new class of laser hosts-the silicate oxyapatites. For Ca2La8(SiO4)6O2 the five independent elastic constants obtained from sound velocity measurements are C11=1.71, C12=0.62, C33=1.71, C44=0.52, and C13=0.39×1012 dyn/cm2, the thermal expansion coefficients at 300 K are 8.9×10−6 and 6.6×10−6 K−1 for the [101̄0] and [0001] directions, respectively, and the room-temperature conductivity is about 0.019 W cm−1 K−1. Sound velocity and thermal expansion data suggest a Debye temperature between 400 and 500 K.

A novel CMAS‐resistant material based on thermodynamic equilibrium design: Apatite‐type Gd10(SiO4)6O3

“…The dense region consists of large grains of 10‐50 μm, and the porous region consists of fine grains of 1‐2 μm. This type of microstructure can be attributed to the orientational growth of apatite materials . EDS analysis indicates that both regions are Gd 10 (SiO 4 ) 6 O 3 .…”

“…This type of microstructure can be attributed to the orientational growth of apatite materials. 31 EDS analysis indicates that both regions are Gd 10 (SiO 4 ) 6 O 3 . This agrees with the XRD pattern for the as-sintered Gd 10 (SiO 4 ) 6 O 3 pellet, which shows a single apatite phase, as shown in Figure 1B.…”

Effect of CMAS Deposits on MOCVD Coatings in the System Y2O3–ZrO2: Phase Relationships

“…Energy dispersive X‐ray spectroscopy analysis of the oxyapatite crystals formed above the Y 2 O 3 coating yield an average composition of 49.5 mol% SiO 2 , 16.2 mol% CaO, 34.3 mol% Y 2 O 3. This result matches the stoichiometry of Ca 2 Y 8 (SiO 4 ) 6 O 2 reported in the literature . Oxyapatite crystals formed above the Y 2 O 3 ·ZrO 2 coating hold a significant amount of ZrO 2 : EDS yields an average composition of 47.0 mol% SiO 2 , 19.9 mol% CaO, 26.6 mol% Y 2 O 3 , and 6.5 mol% ZrO 2 .…”

Volcanic Ash‐Induced Decomposition of EB‐PVD Gd2Zr2O7 Thermal Barrier Coatings to Gd‐Oxyapatite, Zircon, and Gd,Fe‐Zirconolite

“…The influence of Gd‐oxyapatite can be discussed in the light of literature data given for similar compounds of the apatite‐type rare‐earth silicate family. Work on isostructural, single‐crystal Ca 2 La 8 (SiO 4 ) 6 O 2 revealed anisotropic coefficients of thermal expansion (CTE) of 8.9 ppm along the a‐ and 6.6 ppm along the c ‐axis, respectively . This is considerably lower than the expansion of Gd 2 Zr 2 O 7 having a CTE of ~12 ppm.…”