Influence of growth conditions on the optical, electrical resistivity and piezoelectric properties of Ca₃TaGa₃Si₂O₁₄ single crystals

Abstract

(CTGS) single crystals are grown by the Czochralski technique and investigated in detail for high temperature sensor applications. The influence of the oxygen partial pressure during the growth on material properties is investigated by the use of Ir crucibles, as well as Pt ones. Colorless crystals are obtained, indicating that the typical yellowish coloration of CTGS crystals is related with the use of Ir-crucibles. Colored crystals present three absorption bands at 340, 450 and 1790 nm, however, related crystal defects do not affect the electrical properties of grown crystals. Dielectric and piezoelectric properties do not vary significantly with the growth conditions. Instead, it is found that the electrical resistivity depends on the oxygen partial pressure and it is higher for CTGS crystals grown under oxygen-less atmosphere.

Resistivity and piezoelectric properties of Ca3TaGa1.5Al1.5Si2O14 single crystals for high temperature sensors

“…For the sake of comparison, the linear thermal expansion coefficients were estimated and are listed in Table 3 together with those of LTGA, CTGS, CTAS and a-quartz crystals. 1,12,14,18 As can be seen, compared to other single crystals, the thermal expansion coefficients of CTGAS along a-and c-axes are quite close, namely 8.44 Â 10 À6 and 8.58 Â 10 À6 K À1 , respectively. The similarity of these two values indicates a small anisotropy on thermal expansion, which is benecial to avoid cracking for HT applications.…”

“…5 shows the lattice constants of CTGAS crystal at RT, together with the reported values for CTGS (Al content, x ¼ 0) and CTAS (Al content, x ¼ 3). 14,18 The insert illustrates the cation coordination of CTGAS crystal. As can be seen in Fig.…”

“…1 Therefore, the CTGS single crystal is attracting much attention for HT sensors. [13][14][15] Recently we have shown that the resistivity and piezoelectric coefficient d 11 of CTGS can be gradually enhanced by the incorporation of Al on the Ga site. We have even succeeded to grow the fully Al-substituted Ca 3 -TaAl 3 Si 2 O 14 (CTAS) crystal, which exhibits the best performance for HT applications.…”

Mo-La2O3 Multilayer Metallization Systems for High Temperature Surface Acoustic Wave Sensor Devices

“…Besides this, the electrical resistivity (bulk Mo ρMo≈5.50.166667emsans-serifμsans-serifΩcm at 300 K) and the thermal expansion coefficient (bulk Mo αthMo≈4.8×10−6 K−1 at 300 K) are much lower in Mo compared with Pt (ρPt≈10.80.166667emsans-serifμsans-serifΩcm, αthPt≈8.8×10−6 K−1 both at 300 K). Since sans-serifαthMo is closer to the value of CTGS (αthCTGS=4−5×10−6 K−1 in the basal plane at 300 K [26,27]) lower thermally induced mechanical stresses are expected in Mo-CTGS systems as compared to Pt on CTGS. All these properties make Mo based material systems very promising for the high-temperature SAW technology.…”

Crystal growth and optical properties of Ca3TaGa3Si2O14 single crystals

“…CGG is used as a piezoelectric material for filters with large pass bandwidths, devices with highfrequency stability, and high-temperature piezoelectric sensors. [1][2][3][4][5][6][7][8][9][10] These crystals from the so-called langasite family are represented by the formula A 3 BC 3 D 2 O 14 , where A is the decahedral site, B is the octahedral site, and C and D are two different tetrahedral sites. According to the ionic distribution, langasites are divided into ordered and disordered types.…”