Abstract The crystal structure of the quaternary compound CuVInSe 3, belonging to the system (CuInSe 2) 1 - x(VSe) x with x = 1 / 2, was analyzed using X-ray powder diffraction data. This material was synthesized by the melt and anneal method and crystallizes in the tetragonal space group P 4 ¯2c (N ∘ 112), with unit cell parameters a = 5.7909 ( 4 ) Å, c = 11.625 ( 1 ) Å, V = 389.84 ( 5 ) Å 3. The Rietveld refinement of 25 instrumental and structural variables led to R exp = 6.6%, R p = 8.7 %, R w p = 8.8 % and S = 1.3 for 4501 step intensities, and 153 independent reflections. This compound has a normal adamantane structure and is isostructural with CuFeInSe 3. The DTA indicates that this compound melts at 1332 K.

Chalcogenide alloys CuMnAlSe3, CuMnGaSe3 and CuMnInSe3, new members of the semiconductor system I-II-III-VI3, were synthetized and structurally characterized by the Rietveld method using X-ray powder diffraction data. All compounds crystallize in the tetragonal space group P4 2c (Nº 112) with a CuFeInSe3-type structure.

Se prepararon muestras policristalinas de CuCo2InTe4 and CuNi2InTe4 en su valor nominal por el método de fusión y recocido, y los productos fueron caracterizados por las técnicas de difracción de rayos X y SQUID. Se encontró que CuCo2InTe4 and CuNi2InTe4 cristalizan en una estructura tetragonal, grupo espacial (Nº 121), Z = 2, tipo estannita, con presencia de los binarios CoTe y NiTe como fases secundarias, respectivamente. El comportamiento magnético de CuCo2InTe4 es de tipo superparamagnético con una temperatura de irreversibilidad de ~450K y un campo coercitivo máximo de 35 Oe a 2K; mientras que CuNi2InTe4 presenta dos componentes magnéticas, una diamagnética y otra ferromagnética débil.

Polycrystalline samples of nominal CuCo2InTe4 and CuNi2InTe4 were prepared by the melt and anneal method and the products characterized by powder X-ray diffraction and SQUID techniques. It was found that CuCo2InTe4 and CuNi2InTe4 crystallize in the tetragonal space group (Nº 121), Z = 2, in a stannite-type structure, with the binaries CoTe and NiTe as secondary phases, respectively. The magnetic behavior of CuCo2InTe4 is that of a superparamagnetic state with an irreversibility temperature of ~450K and a maximum coercive field of 35 Oe at 2K; whereas CuNi2InTe4 shows two magnetic components, one diamagnetic an another weak ferromagnetic.

The crystal structure of the chalcogenide compounds CuCo2InTe4 and CuNi2InTe4, two new members of the I-II2-III-VI4 family, were characterized by Rietveld refinement using X-ray powder diffraction data. Both materials crystallize in the tetragonal space group I4 2m (No. 121), Z = 2, with a stannite-type structure, with the binaries CoTe and NiTe as secondary phases.

Se prepararon muestras policristalinas (peso ~ 1 g) de las aleaciones Cu2GeTe4 y Cu2SnTe4 por el método de fusión y recocido y los productos caracterizados por las técnicas de Difracción de Rayos X (DRX ) , Análisis Térmico Diferencial (ATD), Microscopía Electrónica de Barrido (MEB) y espectroscopía de reflectancia óptica difusa UV / VIS / CIR. Se encontró que : a) Cu2GeTe4 y Cu2SnTe4 cristalizan en una estructura ortorrómbica ( g.e. Imm2; Nº 44 ) con parámetros de red a = 5,9281 (4) Å , b = 4.2211 (6) Å , c = 12.645 (5) Å y a = 6.0375 (6) Å , b = 4,2706 (3) Å , c = 12.844 (1) Å , respectivamente ; b) ambas aleaciones muestran dos transiciones térmicas : 762 y 636K al calentar y ; 700 y 578K tras el enfriamiento para Cu2GeTe4 ; 702 y 636K al calentar y ; 650 y 590K tras el enfriamiento para Cu2SnTe4 ; c) ambas aleaciones presentan importantes desviaciones estequiométricas en sus cationes: Cu (~35%), Ge (7.2%) and Sn (26.4%) y menor que el error experimental para el anión Te; y d) las brechas ópticas de energía medidas fueron 0.63 y 0.53 eV para Cu2SnTe4 y Cu2GeTe4, respectivamente.

Polycrystalline samples (weight ~ 1g) of Cu2GeTe4 and Cu2SnTe4 alloys were prepared by the usual melt and anneal method and the products characterized by X-Ray Diffraction (XRD), Differential Thermal Analysis (DTA), Scanning Electron Microscopy (SEM) and Optical Diffuse Reflectance UV/VIS/NIR Spectroscopy techniques. It was found that: a) Cu2GeTe4 and Cu2SnTe4 crystallize in an orthorhombic structure (s.g. Imm2; Nº 44) with lattice parameters a=5.9281(4) Å, b=4.2211(6) Å, c=12.645(5) Å and a=6.0375(6) Å, b= 4.2706 (3) Å, c=12.844(1) Å, respectively; b) both alloys show two thermal transitions: 762 and 636K upon heating and; 700 and 578K upon cooling for Cu2GeTe4; 702 and 636K upon heating and; 650 and 590K upon cooling for Cu2SnTe4; c) both alloys present large deviations of stoichiometry for the cations Cu (~35%), Ge (7.2%) and Sn (26.4%) and minor deviation within the experimental error, for the anion Te; and, d) the measured optical band gaps were 0.63 and 0.53 eV for Cu2SnTe4 and Cu2GeTe4, respectively.

Se investigó la dependencia con la presión (hasta 30 Kb y a temperatura ambiente) de las frecuencias y los anchos de línea de los modos Raman activos del compuesto ternario Cu3NbS4 usando una celda de presión de diamante y la técnica de micro-Raman focalizado. Se observaron claramente siete modos de frecuencia Raman-activos en el rango de presión estudiado y se reportan sus variaciones en función. Se confirmó una transición de fase estructural a 25 ± 5 Kb anteriormente reportada en literatura.

Pressure dependence of Raman-active mode frequencies and linewidths in Cu3NbS4 ternary compound has been investigated up to 30 Kb (at room temperature) using focalized micro-Raman technique in a diamond anvil high pressure cell. Seven Raman-active modes frequencies were clearly observed in the pressure range studied and the variation of their respective Raman shift frequency as a function of pressure were given. A structural phase transition at 25 ± 5 Kb previously reported in literature was confirmed.

Se prepararon muestras policristalinas del sistema de aleaciones (CuGaSe2)1-x (FeSe)x en el rango de composiciones (0≤x≤0,5) por la técnica de fusión y recocido. Los productos fueron analizados usando las técnicas de Difracción de Rayos X (DRX) y Análisis Térmico Diferencial (ATD). Del análisis de los resultados experimentales se propone un diagrama de fases, T-x, en la región de composiciones cercana al CuGaSe2

Polycrystalline samples of the (CuGaSe2)1-x (FeSe)x alloy system in the composition range (0≤x≤0.5) were prepared by the melt and anneal technique. X-Ray Diffraction (XRD) and Differential Thermal Analysis (DTA) techniques were used to characterize the products. From the analysis of the experimental results a T-x phase diagram is proposed in the CuGaSe2-rich field (0≤x≤0.5)

Las medidas de absorción óptica en función de la temperatura (300 hasta 750)K sobre muestras semiconductoras de brecha de energía directa CuInVI2 (S, Se y Te) fueron realizadas en el espectro de luz visible. Estos resultados son utilizados para determinar el valor de la brecha fundamental de energía directa Eg en función de la temperatura T, por medio de modelos teóricos clásicos. El parámetro dEg/dT obtenido en el rango de altas temperaturas en los semiconductores ternarios CuInS2, CuInSe2 y CuInTe2 son -3.3x10-4eVK-1, -2.1x10-4eVK-1 y -5.3x10-4eVK-1 respectivamente, estos resultados serán comparados con los reportados hasta los momentos en rangos menores de temperaturas (T<300K)

Optical absorption measurements as a function of high temperature (300 to 750)K on semiconductor direct energy gap CuInVI2 (S, Se and Te) were performed in the visible light spectrum. These results are used to determine the value of the fundamental direct energy gap Eg as a function of temperature T, through classical theoretical models. The dEg/dT parameter obtained in the range of high temperature in the ternary semiconductor compounds CuInS2, CuInSe2 and CuInTe2 are -3.3x10-4eVK-1, -2.1x10-4eVK-1 and -5.3x10-4eVK-1 respectively, these results will be compared with those reported to date in lower ranges of temperatures (T <300K)