Scandium and aluminum substitution and energy transfer processes in the undoped and Ce-doped <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">Y</mml:mi> </mml:mrow> <mml:mn>3</mml:mn> </mml:

The structural and scintillation properties of pure and Ce-doped <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:msub> <a:mi mathvariant="normal">Y</a:mi> <a:mn>3</a:mn> </a:msub> <a:msub> <a:mi mathvariant="normal">Sc</a:mi> <a:mi>x</a:mi> </a:msub> <a:msub> <a:mi mathvariant="normal">Al</a:mi> <a:mrow> <a:mn>5</a:mn> <a:mo>−</a:mo> <a:mi>x</a:mi> </a:mrow> </a:msub> <a:msub> <a:mi mathvariant="normal">O</a:mi> <a:mn>12</a:mn> </a:msub> </a:mrow> </a:math> <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"> <f:mrow> <f:mo>(</f:mo> <f:mi>x</f:mi> <f:mo>=</f:mo> <f:mn>0</f:mn> <f:mo>,</f:mo> <f:mo> </f:mo> <f:mn>0.05</f:mn> <f:mo>,</f:mo> <f:mo> </f:mo> <f:mn>1.16</f:mn> <f:mo>,</f:mo> <f:mo> </f:mo> <f:mtext>and</f:mtext> <f:mo> </f:mo> <f:mn>2</f:mn> <f:mo>)</f:mo> </f:mrow> </f:math> crystals were systematically investigated. High-resolution <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"> <g:mmultiscripts> <g:mi>Sc</g:mi> <g:mprescripts/> <g:none/> <g:mn>45</g:mn> </g:mmultiscripts> </g:math> and <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"> <h:mmultiscripts> <h:mi>Al</h:mi> <h:mprescripts/> <h:none/> <h:mn>27</h:mn> </h:mmultiscripts> </h:math> magic angle spinning nuclear magnetic resonance spectroscopy revealed that <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"> <i:mrow> <i:mi mathvariant="normal">S</i:mi> <i:msup> <i:mrow> <i:mi mathvariant="normal">c</i:mi> </i:mrow> <i:mrow> <i:mn>3</i:mn> <i:mo>+</i:mo> </i:mrow> </i:msup> </i:mrow> </i:math> ions predominantly occupy octahedral sites, effectively replacing <l:math xmlns:l="http://www.w3.org/1998/Math/MathML"> <l:mrow> <l:mi mathvariant="normal">A</l:mi> <l:msup> <l:mrow> <l:mi mathvariant="normal">l</l:mi> </l:mrow> <l:mrow> <l:mn>3</l:mn> <l:mo>+</l:mo> </l:mrow> </l:msup> </l:mrow> </l:math> ions, while antisite Sc at Y dodecahedral positions remains below 0.2 at.%. Sc incorporation into <o:math xmlns:o="http://www.w3.org/1998/Math/MathML"> <o:mrow> <o:msub> <o:mi mathvariant="normal">Y</o:mi> <o:mn>3</o:mn> </o:msub> <o:msub> <o:mi mathvariant="normal">Al</o:mi> <o:mn>5</o:mn> </o:msub> <o:msub> <o:mi mathvariant="normal">O</o:mi> <o:mn>12</o:mn> </o:msub> </o:mrow> </o:math> induces strong exciton emission at 320–324 nm, nearly 10 times higher than that of reference <s:math xmlns:s="http://www.w3.org/1998/Math/MathML"> <s:mrow> <s:msub> <s:mi mathvariant="normal">Bi</s:mi> <s:mn>4</s:mn> </s:msub> <s:msub> <s:mi mathvariant="normal">Ge</s:mi> <s:mn>3</s:mn> </s:msub> <s:msub> <s:mi mathvariant="normal">O</s:mi> <s:mn>12</s:mn> </s:msub> </s:mrow> </s:math> (BGO) crystal, even at low Sc concentrations (5 at.%). <w:math xmlns:w="http://www.w3.org/1998/Math/MathML"> <w:mrow> <w:mi mathvariant="normal">C</w:mi> <w:msup> <w:mrow> <w:mi mathvariant="normal">e</w:mi> </w:mrow> <w:mrow> <w:mn>3</w:mn> <w:mo>+</w:mo> </w:mrow> </w:msup> </w:mrow> </w:math> doping introduces characteristic <z:math xmlns:z="http://www.w3.org/1998/Math/MathML"> <z:mrow> <z:mn>5</z:mn> <z:msup> <z:mi>d</z:mi> <z:mn>1</z:mn> </z:msup> <z:mo>→</z:mo> <z:mn>4</z:mn> <z:mi>f</z:mi> </z:mrow> </z:math> emission at 518 nm, accelerates scintillation decay, and in combination with <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML"> <ab:mrow> <ab:mi mathvariant="normal">M</ab:mi> <ab:msup> <ab:mrow> <ab:mi mathvariant="normal">g</ab:mi> </ab:mrow> <ab:mrow> <ab:mn>2</ab:mn> <ab:mo>+</ab:mo> </ab:mrow> </ab:msup> </ab:mrow> </ab:math> codoping, promotes the formation of <db:math xmlns:db="http://www.w3.org/1998/Math/MathML"> <db:mrow> <db:mi mathvariant="normal">C</db:mi> <db:msup> <db:mrow> <db:mi mathvariant="normal">e</db:mi> </db:mrow> <db:mrow> <db:mn>4</db:mn> <db:mo>+</db:mo> </db:mrow> </db:msup> </db:mrow> </db:math> ions that enable a fast radiative de-excitation pathway. <gb:math xmlns:gb="http://www.w3.org/1998/Math/MathML"> <gb:mrow> <gb:msub> <gb:mi mathvariant="normal">Y</gb:mi> <gb:mn>3</gb:mn> </gb:msub> <gb:msub> <gb:mi mathvariant="normal">Sc</gb:mi> <gb:mn>2</gb:mn> </gb:msub> <gb:msub> <gb:mi mathvariant="normal">Al</gb:mi> <gb:mn>3</gb:mn> </gb:msub> <gb:msub> <gb:mi mathvariant="normal">O</gb:mi> <gb:mn>12</gb:mn> </gb:msub> </gb:mrow> </gb:math> : Ce exhibits a maximum scintillation light yield of 80–84% relative to BGO with a mean decay time of 85–110 ns. Thermostimulated liminescence and electron paramagnetic resonance studies indicate that holes are mainly trapped at oxygen ions near Sc ions ( <lb:math xmlns:lb="http://www.w3.org/1998/Math/MathML"> <lb:msup> <lb:mrow> <lb:mi mathvariant="normal">O</lb:mi> </lb:mrow> <lb:mo>−</lb:mo> </lb:msup> </lb:math> centers), while electrons are primarily localized at Sc antisite ions near oxygen vacancies ( <nb:math xmlns:nb="http://www.w3.org/1998/Math/MathML"> <nb:mrow>