将svg代码的path属性应用于按钮内容，去掉按钮边框，并且自适应svg大小，以下实现的是一个旋转按钮。
svg代码如下(iconfont下载)：

<svg t="1710741485848" class="icon" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="4468" width="32" height="32"><path d="M938.336973 255.26894c-16.685369-6.020494-35.090879 2.752226-40.939358 19.437594l-24.770032 69.493701c-29.070385-65.537376-74.998152-123.162103-133.48295-166.337645-185.947253-137.611288-450.848984-100.112212-590.180413 83.942886C81.534688 350.908785 52.980346 460.653788 68.805644 570.742819c15.825298 110.605073 74.48211 208.481102 164.789518 275.394591 75.686209 55.904586 164.273476 83.082815 252.172686 83.082815 128.494541 0 255.26894-57.624727 338.007727-166.853687 36.639006-48.335965 61.581052-102.348396 74.48211-160.833193 3.78431-17.373425-7.224593-34.402822-24.426004-38.187133-17.201411-3.78431-34.402822 7.052579-38.187133 24.426004-10.836889 49.36805-31.994625 95.123803-62.957164 135.891147-118.173694 156.016798-342.996136 187.839409-500.90509 70.869814-76.546279-56.592642-126.086343-139.33143-139.503444-232.907106-13.417101-93.059634 10.664875-185.775239 67.77356-261.11742C318.05409 144.491853 542.704519 112.497228 700.785486 229.466823c57.280699 42.315471 100.112212 100.972283 123.334117 167.197715l-110.261045-43.003528c-16.513355-6.364522-35.090879 1.720141-41.627415 18.233496-6.536536 16.513355 1.720141 35.090879 18.233496 41.627415l162.38132 63.473207c3.78431 1.548127 7.740635 2.236183 11.69696 2.236183 0.516042 0 1.032085-0.172014 1.548127-0.172014 1.204099 0.172014 2.408198 0.688056 3.612296 0.688056 13.245087 0 25.630102-8.256677 30.274483-21.32975l57.796741-161.693264C963.623047 279.694944 955.022342 261.289434 938.336973 255.26894z" fill="#575B66" p-id="4469"></path></svg>

xaml如下：

<UserControl.Resources>
	<Style x:Key="NoBorderButton" TargetType="Button">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="Button">
                        <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
    </Style>
<UserControl.Resources>
<Button Cursor="Hand" Height="20" Width="20" Style="{StaticResource NoBorderButton}">
	<Grid>
		<Viewbox Stretch="Uniform">
			<Path Data="M938.336973 255.26894c-16.685369-6.020494-35.090879 2.752226-40.939358 19.437594l-24.770032 69.493701c-29.070385-65.537376-74.998152-123.162103-133.48295-166.337645-185.947253-137.611288-450.848984-100.112212-590.180413 83.942886C81.534688 350.908785 52.980346 460.653788 68.805644 570.742819c15.825298 110.605073 74.48211 208.481102 164.789518 275.394591 75.686209 55.904586 164.273476 83.082815 252.172686 83.082815 128.494541 0 255.26894-57.624727 338.007727-166.853687 36.639006-48.335965 61.581052-102.348396 74.48211-160.833193 3.78431-17.373425-7.224593-34.402822-24.426004-38.187133-17.201411-3.78431-34.402822 7.052579-38.187133 24.426004-10.836889 49.36805-31.994625 95.123803-62.957164 135.891147-118.173694 156.016798-342.996136 187.839409-500.90509 70.869814-76.546279-56.592642-126.086343-139.33143-139.503444-232.907106-13.417101-93.059634 10.664875-185.775239 67.77356-261.11742C318.05409 144.491853 542.704519 112.497228 700.785486 229.466823c57.280699 42.315471 100.112212 100.972283 123.334117 167.197715l-110.261045-43.003528c-16.513355-6.364522-35.090879 1.720141-41.627415 18.233496-6.536536 16.513355 1.720141 35.090879 18.233496 41.627415l162.38132 63.473207c3.78431 1.548127 7.740635 2.236183 11.69696 2.236183 0.516042 0 1.032085-0.172014 1.548127-0.172014 1.204099 0.172014 2.408198 0.688056 3.612296 0.688056 13.245087 0 25.630102-8.256677 30.274483-21.32975l57.796741-161.693264C963.623047 279.694944 955.022342 261.289434 938.336973 255.26894z" Fill="Black" />
		</Viewbox>
		<TextBlock Background="Transparent" Cursor="Hand"></TextBlock>
	</Grid>
</Button>

TextBlock是为了解决只有点击到路径才能触发点击事件问题。
效果如下：