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BaLnTeO (Ln = La, Pr, Nd, Sm, and Eu) double perovskites were synthesized via solid-state ceramic route. Preliminary X-ray diffraction studies indicated a pseudocubic structure with lattice parameters ranging from 8.55 to 8.44 Å for the substitution of rare earths from La to Eu. Raman spectra show the frequency dependence of various Raman bands with respect to rare-earth substitution and exhibit a significant shift in peaks to higher wavenumber region, which was observed only for symmetric stretching modes of LnO and TeO octahedra. In accordance with observed number of bands and group theoretical predictions, the most likely symmetry of all compounds in the BaLnTeO system was found to be monoclinic with P2 /n space group. Rietveld refinement of the XRD patterns further confirmed the P2 /n space group and also the 1:1 rock salt ordering of the B-site cations. Diffuse reflectance spectra of BaLnTeO showed the optical bandgaps of these compounds between 3.9 and 4.8 eV, indicating the suitability as luminescent host material. The reduction in bandgap energy with lanthanide contraction of rare-earth ions is attributed to the widening of conduction band with octahedral tilting. Photoluminescence (PL) spectra and PL excitation spectra of BaLaEu TeO ( x = 0.025, 0.05, 0.075, 0.1, 0.125, 0.15) were investigated and found to exhibit bright orange-red emission under UV excitation. Chromaticity coordinates closely resemble those of commercial red phosphor SrSiN:Eu, which points toward the possible applicability of these new red phosphors in solid-state lighting industry. Finally, Judd-Ofelt intensity parameters Ω (λ = 2 and 4) were calculated, which indicate that Eu ions occupy the symmetric octahedral B-site of the BaLaTeO.

Monoclinic (P21/n) structure of B-site ordered double perovskites Ba2R2/3TeO6 (R = Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) is elucidated from XRD, Raman and IR spectroscopy. The maximum relative temperature sensitivity of Ba2Y2/3TeO6:Eu3+ between 300–500 K is 0.18% K−1.

Among the different categories of ceramic compounds, perovskites draw worldwide attention amidst researchers due to their interesting properties such as superconductivity, nonlinear optical properties, photoluminescence, ionic conductivity, ferroelectricity, magnetoresistance, catalytic properties, etc. These versatilities in physical properties lead to the emergence of various functional electronic and optoelectronic devices that are capable of doing much better performance than their predecessors. 1 Due to hundreds of functional halide double perovskites reported over the past few years, the definition of perovskites seems inadequate and hence Song et al. categorize perovskites into three groups based on their structure viz., standard-perovskite (having 3D structure and general formula ABX 3 ), low-dimensional (low-D including 2D, 1D, and 0D) perovskites, and perovskite-like halides. 2 The first two consist of corner sharing or discrete octahedra, whereas the latter consist of edge sharing as well as face sharing octahedra. 2 The possibility of substituting cations in either A site or B site of the basic perovskite structure (ABX 3 ) leads to the formation of complex perovskites or generally double perovskites and falls under the category of "standard perovskite." The modifiability in cationic sites induces the development of new functional materials which further enhance the device properties. 1,2 Luminescence in double perovskites is an irresistible area of research and there are plenty of research articles published every year regarding this intriguing physical property. It has substantial applications in the field of photovoltaic devices, photocatalysis, electronic devices such as capacitors, transducers, sensors, lighting devices, etc. 3-8 Among these,

Impurities and growth-related defect structures are mainly responsible for low thermal conductivity of chemical vapor deposited diamond films. Different quality arc-jet-deposited, free-standing diamond samples were obtained from industry. Fourier transform infrared ͑FTIR͒, Raman, and x-ray photoelectron spectroscopy ͑XPS͒ were used to determine the quality of these samples. The nondiamond carbon was estimated from the 1560 cm Ϫ1 broad peak intensity, the CH x integrated peak absorbance, and the C 1s plasmon loss features for Raman, FTIR, and XPS studies, respectively. The diamond quality was also determined from the Raman diamond peak full width at half maximum ͑FWHM͒ and XPS valence band spectra. It was observed that the higher the hydrogen content ͑determined by FTIR͒, the darker the color of the film, the larger the nondiamond 1560 cm Ϫ1 peak intensity, and the larger the FWHM of the Raman diamond peak at 1332 cm Ϫ1 . Negligible difference in the C 1s diamond bulk plasmon loss peak was observed for films of wide ranging quality. The FTIR CH x band exhibited the highest sensitivity to film quality. Impurity-related peaks were observed in the one phonon region of the FTIR spectra and the photoluminescence spectra. The photoluminescence background peak centered at 2.0 eV was found to be strongly related to nondiamond carbon impurities. It is shown that a combination of different analytical tools is required to determine diamond quality.