Pd and octahedra do not get along: Square planar [PdS4] units in non-centrosymmetric La6PdSi2S14

Non‐Linear Optical Properties of the (RE)3CuGeS7 Family of Compounds

“…While most infrared NLO materials have band gaps around 2.5 eV, there are reported phases with narrow band gaps that still exhibit good second-harmonic generation (SHG) and laser damage threshold (LDT) properties such as La 6 PdSi 2 S 14 , E g ~1.41 eV. [13] Figure 4 shows SHG and LDT data for the (RE) 3 CuGeS 7 compositions. Phases with RE=La, [13] Sm, and Gd have good SHG responses as compared to the standard AgGaS 2 and are also phase-matchable.…”

“…[13] Figure 4 shows SHG and LDT data for the (RE) 3 CuGeS 7 compositions. Phases with RE=La, [13] Sm, and Gd have good SHG responses as compared to the standard AgGaS 2 and are also phase-matchable. Furthermore, the Sm and Gd samples have enhanced LDT (83.5 and 89 MW/cm 2 ) as compared to both, the standard AgGaS 2 (29.6 MW/cm 2 ) and La analogue (41.5 MW/cm 2 ), showing further benefits of composition optimization.…”

“…All of the phases are semiconductors with direct band gaps in the visible range 2.12–2.67 eV, which are comparable to the band gap of the AgGaS 2 standard (2.5 eV). While most infrared NLO materials have band gaps around 2.5 eV, there are reported phases with narrow band gaps that still exhibit good second‐harmonic generation (SHG) and laser damage threshold (LDT) properties such as La 6 PdSi 2 S 14 , E g ∼1.41 eV [13] …”

“…Details of the arcmelting procedure can be found elsewhere. [12,13,[27][28][29][30] Utilization of precursor synthesis for such quaternary sulfides is discussed more in depth in [12] and compared to synthesis from elements and binary sulfides for select compositions. Phase compositions of the precursor materials can be found in Table 2.…”

“…Quaternary sulfides of the type (RE) 6 (TM) x (T) 2 Q 14 (RE = rareearth; TM = transition metals; T=Si, Ge, Sn, Be, Fe, Zn, Sm, Yb, B, Al, Ga, and In; Q=S and Se) are a large class of compounds which adopt the non-centrosymmetric, polar, and chiral P6 3 space group. [11][12][13] For coinage metals (group 11) with + 1 oxidation state, x = 2 and the aforementioned formula (6-2-2-14) can be reduced to the (RE) 3 (TM)TQ 7 notation (3-1-1-7), which will be used below. La 3 CuGeS 7 was previously identified as a promising NLO material with good SHG and LDT properties compared to its analogues with T=Si or Sn and other transition metals.…”