From Serendipity to Rational Design: Tuning the Blue Trigonal Bipyramidal Mn3+ Chromophore to Violet and Purple through Application of Chemical Pressure
Jun Li, Simon Lorger, Judith K. Stalick, Arthur W. Sleight, M. A. Subramanian
We recently reported that an allowed d-d transition of trigonal bipyramidal (TBP) Mn3+ is responsible for the bright blue color in the YIn10xMnxO3 solid solution. The crystal field splitting between a'(dz2) and e'(dx2'y2, Dxy) energy levels is very sensitive to the apical Mn-O distance. we therefore applied chemical pressure to compress the apical Mn-O distance in YIn10xMnxO3, move the allowed d-d transition to higher energy, and thereby tune the color from blue to violet/purple. This was accomplished by substituting smaller cations such as Ti4+/Zn2+ and Al3+ onto the TBP In/Mn site, which yielded novel violet/purple phases. The general formula is YIn1-x-2y-zMnxTiyAlzO3 (x=0.0050.2, y=0.10.4 and z less than or equal to}0.1}, where the color darkens with the increasing amount of Mn. Higher y or small additions of Al provides a more reddish hue to the resulting purple colors. Substituting other rare earth cations for Y has little impact on color. Crystal structure analysis by neutron powder diffraction confirms a shorter apical Mn-O distance compared with that in the blue YIn1-xMnxO3. Magnetic susceptibility measurements verify the 3+ oxidation state for Mn. Diffuse reflection spectra were obtained over the wavelength 200 nm to 2500 nm. All samples show excellent near infrared reflectance comparable to that of commercial TiO2, making them ideal for cool pigment applications such as energy efficient roofs of buildings and cars where reducing solar heat to save energy is desired. Compared with commercial purple pigments, such as Co3(PO4)2, our environmentally benign pigments are much more thermally stable and chemically inert.
, Lorger, S.
, Stalick, J.
, Sleight, A.
and Subramanian, M.
From Serendipity to Rational Design: Tuning the Blue Trigonal Bipyramidal Mn<sup>3+</sup> Chromophore to Violet and Purple through Application of Chemical Pressure, Inorganic Chemistry, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=921441
(Accessed December 11, 2023)